# `ftputil` -- a high-level FTP client library

Version: | 5.0.3
Date: | 2022-01-26
Summary: | high-level FTP client library for Python
Keywords: | FTP, `ftplib` substitute, virtual filesystem, pure Python
Author: | Stefan Schwarzer <sschwarzer@sschwarzer.net>

Contents

- Introduction
- `ftputil` features
- Exception hierarchy
- `FTPHost` objects
  - Construction
    - Introduction
    - Session factories
  - Directory and file names
  - Hidden files and directories
  - `FTPHost` attributes and methods
    - Attributes
    - Remote file system navigation
    - Uploading and downloading files
    - Time zone correction
    - Creating and removing directories
    - Removing files and links
    - Retrieving information about directories, files and links
    - Local caching of file system information
    - Iteration over directories
    - Other methods
- File-like objects
  - Construction
    - Basics
  - Attributes and methods
- `FTPHost` instances vs. FTP connections
- Writing directory parsers
- FAQ / Tips and tricks
  - Where can I get the latest version?
  - Is there a mailing list on `ftputil`?
  - I found a bug! What now?
  - Does `ftputil` support TLS?
  - How do I connect to a non-default port?
  - How do I set active or passive mode?
  - How can I debug an FTP connection problem?
  - Conditional upload/download to/from a server in a different time zone
  - When I use `ftputil`, all I get is a `ParserError` exception
  - `isdir`, `isfile` or `islink` incorrectly return `False`
  - I don't find an answer to my problem in this document
- Bugs and limitations
- Files
- References
- Authors

# Introduction

The `ftputil` module is a high-level interface to the ftplib module. The FTPHost objects generated from it allow many operations similar to those of os, os.path and shutil.

Example:

    import ftputil

    # Download some files from the login directory.
    with ftputil.FTPHost("ftp.domain.com", "user", "password") as ftp_host:
        names = ftp_host.listdir(ftp_host.curdir)
        for name in names:
            if ftp_host.path.isfile(name):
                ftp_host.download(name, name)  # remote, local
        # Make a new directory and copy a remote file into it.
        ftp_host.mkdir("newdir")
        with ftp_host.open("index.html", "rb") as source:
            with ftp_host.open("newdir/index.html", "wb") as target:
                ftp_host.copyfileobj(source, target)  # similar to shutil.copyfileobj

Also, there are FTPHost.lstat and FTPHost.stat to request size and modification time of a file. The latter can also follow links, similar to os.stat. FTPHost.walk and FTPHost.path.walk work, too.

# `ftputil` features

- Method names are familiar from Python's `os`, `os.path` and `shutil` modules. For example, use `os.path.join` to join paths for a local file system and `ftp_host.path.join` to join paths for a remote FTP file system.
- Remote file system navigation (`getcwd`, `chdir`)
- Upload and download files (`upload`, `upload_if_newer`, `download`, `download_if_newer`)
- Time zone synchronization between client and server (needed for `upload_if_newer` and `download_if_newer`)
- Create and remove directories (`mkdir`, `makedirs`, `rmdir`, `rmtree`) and remove files (`remove`)
- Get information about directories, files and links (`listdir`, `stat`, `lstat`, `exists`, `isdir`, `isfile`, `islink`, `abspath`, `dirname`, `basename` etc.)
- Iterate over remote file systems (`walk`)
- Local caching of results from `lstat` and `stat` calls to reduce network access (also applies to `exists`, `getmtime` etc.).
- Read files from and write files to remote hosts via file-like objects (`FTPHost.open`; the generated file-like objects have the familiar methods like `read`, `readline`, `readlines`, `write`, `writelines` and `close`. You can also iterate over these files line by line in a `for` loop.

# Exception hierarchy

The exceptions are in the namespace of the `ftputil.error` module, e. g. `ftputil.error.TemporaryError`.

The exception classes are organized as follows:

    FTPError
        FTPOSError(FTPError, OSError)
            PermanentError(FTPOSError)
                CommandNotImplementedError(PermanentError)
            TemporaryError(FTPOSError)
        FTPIOError(FTPError)
        InternalError(FTPError)
            InaccessibleLoginDirError(InternalError)
            NoEncodingError(InternalError)
            ParserError(InternalError)
            RootDirError(InternalError)
            TimeShiftError(InternalError)

and are described here:

- `FTPError`

  is the root of the exception hierarchy of the module.

- `FTPOSError`

  is derived from `OSError`. This is for similarity between the os module and `FTPHost` objects. Compare

      try:
          os.chdir("nonexisting_directory")
      except OSError:
          ...

  with

      host = ftputil.FTPHost("host", "user", "password")
      try:
          host.chdir("nonexisting_directory")
      except OSError:
          ...

  Imagine a function

      def func(path, file):
          ...

  which works on the local file system and catches `OSErrors`. If you change the parameter list to

      def func(path, file, os=os):
          ...

  where `os` denotes the `os` module, you can call the function also as

      host = ftputil.FTPHost("host", "user", "password")
      func(path, file, os=host)

  to use the same code for both a local and remote file system. Another similarity between `OSError` and `FTPOSError` is that the latter holds the FTP server return code in the `errno` attribute of the exception object and the error text in `strerror`.

- `PermanentError`

  is raised for 5xx return codes from the FTP server. This corresponds to `ftplib.error_perm` (though `PermanentError` and `ftplib.error_perm` are not identical).

- `CommandNotImplementedError`

  indicates that an underlying command the code tries to use is not implemented. For an example, see the description of the FTPHost.chmod method.

- `TemporaryError`

  is raised for FTP return codes from the 4xx category. This corresponds to `ftplib.error_temp` (though `TemporaryError` and `ftplib.error_temp` are not identical).

- `FTPIOError`

  denotes an I/O error on the remote host. This appears mainly with file-like objects that are retrieved by calling `FTPHost.open`. Compare

      >>> try:
      ...     f = open("not_there")
      ... except IOError as obj:
      ...     print(obj.errno)
      ...     print(obj.strerror)
      ...
      2
      No such file or directory

  with

      >>> ftp_host = ftputil.FTPHost("host", "user", "password")
      >>> try:
      ...     f = ftp_host.open("not_there")
      ... except IOError as obj:
      ...     print(obj.errno)
      ...     print(obj.strerror)
      ...
      550
      550 not_there: No such file or directory.

  As you can see, both code snippets are similar. However, the error codes aren't the same.

- `InternalError`

  subsumes exception classes for signaling errors due to limitations of the FTP protocol or the concrete implementation of `ftputil`.

- `InaccessibleLoginDirError`

  This exception is raised if the directory in which "you" are placed upon login is not accessible, i. e. a `chdir` call with the directory as argument would fail.

- `NoEncodingError`

  is raised if an FTP session instance doesn't have an `encoding` attribute (see also session factories).

- `ParserError`

  is used for errors during the parsing of directory listings from the server. This exception is used by the `FTPHost` methods `stat`, `lstat`, and `listdir`.

- `RootDirError`

  Because of the implementation of the `lstat` method it is not possible to do a `stat` call on the root directory `/`. If you know any way to do it, please let me know. :-)

  This problem does not affect stat calls on items in the root directory.

- `TimeShiftError`

  is used to denote errors which relate to setting the time shift.

# `FTPHost` objects

## Construction

### Introduction

`FTPHost` instances can be created with the following call:

    ftp_host = ftputil.FTPHost(server, user, password, account,
                               session_factory=ftplib.FTP)

The first four parameters are strings with the same meaning as for the FTP class in the `ftplib` module. Usually the `account` and `session_factory` arguments aren't needed though.

`FTPHost` objects can also be used in a `with` statement:

    import ftputil

    with ftputil.FTPHost(server, user, password) as ftp_host:
        print(ftp_host.listdir(ftp_host.curdir))

After the `with` block, the `FTPHost` instance and the associated FTP sessions will be closed automatically.

If something goes wrong during the `FTPHost` construction or in the body of the `with` statement, the instance is closed as well. Exceptions will be propagated (as with `try ... finally`).

### Session factories

The keyword argument `session_factory` may be used to generate FTP connections with other factories than the default `ftplib.FTP`. For example, the standard library of Python 3 contains a class `ftplib.FTP_TLS` which extends `ftplib.FTP` to use an encrypted connection.

In fact, all positional and keyword arguments other than `session_factory` are passed to the factory to generate a new background session. This also happens for every remote file that is opened; see below.

This functionality of the constructor also allows to wrap `ftplib.FTP` objects to do something that wouldn't be possible with the `ftplib.FTP` constructor alone.

As an example, assume you want to connect to another than the default port, but `ftplib.FTP` only offers this by means of its `connect` method, not via its constructor. One solution is to use a custom class as a session factory:

    import ftplib
    import ftputil

    EXAMPLE_PORT = 50001

    class MySession(ftplib.FTP):

        def __init__(self, host, userid, password, port):
            """Act like ftplib.FTP's constructor but connect to another port."""
            ftplib.FTP.__init__(self)
            self.connect(host, port)
            self.login(userid, password)

    # Try _not_ to use an _instance_ `MySession()` as factory, -
    # use the class itself.
    with ftputil.FTPHost(host, userid, password, port=EXAMPLE_PORT,
                         session_factory=MySession) as ftp_host:
        # Use `ftp_host` as usual.
        ...

On login, the format of the directory listings (needed for stat'ing files and directories) should be determined automatically. If not, please enter a ticket.

For the most common uses you don't need to create your own session factory class though. The `ftputil.session` module has a function `session_factory` that can create session factories for a variety of parameters:

    session_factory(base_class=ftplib.FTP,
                    port=21,
                    use_passive_mode=None,
                    encrypt_data_channel=True,
                    encoding=None,
                    debug_level=None)

with

- `base_class` is a base class to inherit a new session factory class from. By default, this is `ftplib.FTP` from the Python standard library.

- `port` is the command channel port. The default is 21, used in most FTP server configurations.

- `use_passive_mode` is either a boolean that determines whether passive mode should be used or `None`. `None` means to let the base class choose active or passive mode.

- `encrypt_data_channel` defines whether to encrypt the data channel for secure connections. This is only supported for the base classes `ftplib.FTP_TLS` and `M2Crypto.ftpslib.FTP_TLS`, otherwise the parameter is ignored.

- `encoding` can be a string to set the encoding of directory and file paths on the remote server. (This has nothing to do with the encoding of file contents!) If you pass a string and your base class is neither `ftplib.FTP` nor `ftplib.FTP_TLS`, the used heuristic in `session_factory` may not work reliably. Therefore, if in doubt, let `encoding` be `None` and define your `base_class` so that it sets the encoding you want.

  Note: In Python 3.9, the default path encoding for `ftplib.FTP` and `ftplib.FTP_TLS` changed from previously "latin-1" to "utf-8". Hence, if you don't pass an `encoding` to `session_factory`, you'll get different path encodings for Python 3.8 and earlier vs. Python 3.9 and later.

  If you're sure that you always use only ASCII characters in your remote paths, you don't need to worry about the path encoding and don't need to use the `encoding` argument.

- `debug_level` sets the debug level for FTP session instances. The semantics is defined by the base class. For example, a debug level of 2 causes the most verbose output for Python's `ftplib.FTP` class.

All of these parameters can be combined. For example, you could use

    import ftplib

    import ftputil
    import ftputil.session

    my_session_factory = ftputil.session.session_factory(
                           base_class=ftpslib.FTP_TLS,
                           port=31,
                           encrypt_data_channel=True,
                           encoding="UTF-8",
                           debug_level=2)

    with ftputil.FTPHost(server, user, password,
                         session_factory=my_session_factory) as ftp_host:
        ...

to create and use a session factory derived from `ftplib.FTP_TLS` that connects on command channel 31, will encrypt the data channel, use the UTF-8 encoding for remote paths and print output for debug level 2.

Note: Generally, you can achieve everything you can do with `ftputil.session.session_factory` with an explicit session factory as described at the start of this section.

## Directory and file names

Note

Keep in mind that this section only applies to directory and file names, not file contents. Encoding and decoding for file contents is handled by the `encoding` argument for FTPHost.open.

Generally, paths can be `str` or `bytes` objects (or PathLike objects wrapping `str` or `bytes`). However, you can't mix different string types (`bytes` and `str`) in one call (for example in `FTPHost.path.join`). If a method gets a string argument (or a string argument wrapped in a PathLike object) and returns one or more strings, these strings will have the same string type (`bytes` or `str`) as the argument(s). Mixing different string types in one call (for example in `FTPHost.path.join`) isn't allowed and will cause a `TypeError`. These rules are the same as for local file system operations.

Although you can pass paths as `str` or `bytes`, the former is recommended. See below for the reason.

If you have directory or file names with non-ASCII characters, you need to be aware of the encoding the session factory (e. g. `ftplib.FTP`) uses. This needs to be the same encoding that the FTP server uses for the paths.

The following diagram shows string conversions on the way from your code to the remote FTP server. The opposite way works analogously, so encoding steps in the diagram become decoding steps and decoding steps in the diagram become encoding steps.

Both "branching points" in the upper and lower part of diagrams are independent, so depending on how you pass paths to ftputil and which file system API the FTP server uses, there are four possible combinations.

      +-----------+       +-----------+
      | Your code |       | Your code |
      +-----------+       +-----------+
           |                    |
           |  str               |  bytes
           v                    v
     +-------------+     +-------------+  decode with encoding of session,
     | ftputil API |     | ftputil API |  e. g. `ftplib.FTP` instance
     +-------------+     +-------------+
             \               /
              \     str     /
               v           v
             +---------------+  encode with encoding
             |  ftplib API   |  specified in `FTP` instance
             +---------------+
                     |
                     |  bytes
                     v
              +-------------+
              | socket API  |
              +-------------+
                 /       \
                /         \                 local / client
     - - - - - / - - - - - \ - - - - - - - - - - - - - - - - - - - - - -
              /             \              remote / server
             /     bytes     \
            v                 v
     +------------+      +------------+  decode with encoding from
     | FTP server |      | FTP server |  FTP server configuration
     +------------+      +------------+
           |                   |
           |  bytes            |  str
           v                   v
    +-------------+      +-------------+
    | remote file |      | remote file |
    | system API  |      | system API  |
    +-------------+      +-------------+
            \                 /
             \      bytes    /
              v             v
           +-------------------+
           |    file system    |
           +-------------------+

As you can see at the top of the diagram, if you use `str` objects (regular unicode strings), there's one fewer decoding step, and so one fewer source of problems. If you use `bytes` objects for paths, ftputil tries to get the encoding for the FTP server from the `encoding` attribute of the session instance (say, an instance of `ftplib.FTP`). If no `encoding` attribute is present, a `NoEncodingError` is raised.

All encoding/decoding steps must use the same encoding, the encoding the server uses (at the bottom of the diagram). If the server uses the bytes from the socket directly, i. e. without an encoding step, you have to use the file system encoding.

Until and including Python 3.8, the encoding implicitly assumed by the `ftplib` module was latin-1, so using `bytes` was the safest strategy. However, Python 3.9 made the `encoding` configurable via an `ftplib.FTP` constructor argument `encoding`, but defaults to UTF-8.

If you don't pass a session factory to the `ftputil.FTPHost` constructor, ftputil will use latin-1 encoding for the paths. This is the same value as in earlier ftputil versions in combination with Python 3.8 and earlier.

Summary:

- If possible, use only ASCII characters in paths.
- If possible, pass paths to ftputil as `str`, not `bytes`.
- If you use a custom session factory, the session instances created by the factory must have an `encoding` attribute with the name of the path encoding to use. If your session instances don't have an `encoding` attribute, ftputil raises a `NoEncodingError` when the session is created.

## Hidden files and directories

Whether ftputil sees "hidden" files and directories (usually files or directories whose names start with a dot) depends on the FTP server configuration. By default, ftputil does not use the `-a` option in the FTP `LIST` command to find hidden files.

To tell the server to list hidden directories and files, set `FTPHost.use_list_a_option` to `True`:

    ftp_host = ftputil.FTPHost(server, user, password, account,
                               session_factory=ftplib.FTP)
    ftp_host.use_list_a_option = True

Caveats:

- If the server doesn't understand the `-a` option at all, the server may interpret `-a` as the name of a file or directory, which can result in odd behavior. Therefore, use `-a` only if you're sure the server you're talking to supports it. Another approach is to have test code for `-a` support and fall back to not using the option.
- Even if the server knows about the `-a` option, the server may be configured to ignore it.

## `FTPHost` attributes and methods

### Attributes

- `curdir`, `pardir`, `sep`

  are strings which denote the current and the parent directory on the remote server. `sep` holds the path separator. Though RFC 959 (File Transfer Protocol) notes that these values may depend on the FTP server implementation, the Unix variants seem to work well in practice, even for non-Unix servers.

  Nevertheless, it's recommended that you don't hardcode these values for remote paths, but use FTPHost.path as you would use `os.path` to write platform-independent Python code for local filesystems. Keep in mind that most, but not all, arguments of `FTPHost` methods refer to remote directories or files. For example, in FTPHost.upload, the first argument is a local path and the second a remote path. Both of these should use their respective path separators.

### Remote file system navigation

- `getcwd()`

  returns the absolute current directory on the remote host. This method works like `os.getcwd`.

- `chdir(directory)`

  sets the current directory on the FTP server. This resembles `os.chdir`, as you may have expected.

### Uploading and downloading files

- `upload(source, target, callback=None)`

  copies a local source file (given by a filename, i. e. a string) to the remote host under the name target. Both `source` and `target` may be absolute paths or relative to their corresponding current directory (on the local or the remote host, respectively).

  The file content is always transferred in binary mode.

  The callback, if given, will be invoked for each transferred chunk of data:

      callback(chunk)

  where `chunk` is a bytestring. An example usage of a callback method is to display a progress indicator.

- `download(source, target, callback=None)`

  performs a download from the remote source file to a local target file. Both `source` and `target` are strings. See the description of `upload` for more details.

- `upload_if_newer(source, target, callback=None)`

  is similar to the `upload` method. The only difference is that the upload is only invoked if the time of the last modification for the source file is more recent than that of the target file or the target doesn't exist at all. The check for the last modification time considers the precision of the timestamps and transfers a file "if in doubt". Consequently the code

      ftp_host.upload_if_newer("source_file", "target_file")
      time.sleep(10)
      ftp_host.upload_if_newer("source_file", "target_file")

  might upload the file again if the timestamp of the target file is precise up to a minute, which is typically the case because the remote datetime is determined by parsing a directory listing from the server. To avoid unnecessary transfers, wait at least a minute between calls of `upload_if_newer` for the same file. If it still seems that a file is uploaded unnecessarily (or not when it should), read the subsection on time shift settings.

  If an upload actually happened, the return value of `upload_if_newer` is a `True`, else `False`.

  Note that the method only checks the existence and/or the modification time of the source and target file; it doesn't compare any other file properties, say, the file size.

  This also means that if a transfer is interrupted, the remote file will have a newer modification time than the local file, and thus the transfer won't be repeated if `upload_if_newer` is used a second time. There are at least two possibilities after a failed upload:

  - use `upload` instead of `upload_if_newer`, or
  - remove the incomplete target file with `FTPHost.remove`, then use `upload` or `upload_if_newer` to transfer it again.

- `download_if_newer(source, target, callback=None)`

  corresponds to `upload_if_newer` but performs a download from the server to the local host. Read the descriptions of download and `upload_if_newer` for more information. If a download actually happened, the return value is `True`, else `False`.

### Time zone correction

For `upload_if_newer` and `download_if_newer` to work correctly, the time zone of the server must be taken into account. By default, ftputil assumes that the timestamps in server listings are in UTC.

- `set_time_shift(time_shift)`

  sets the so-called time shift value, measured in seconds. The time shift here is defined as the difference between the time used in server listings and UTC.

      time_shift = server_time - utc_time

  For example, a server in Berlin/Germany set to the local time (currently UTC+03:00), would require a time shift value of 3 * 3600.0 = 10800.0 seconds to be handled correctly by ftputil's `upload_if_newer` and `download_if_newer`, as well as the `stat` and `lstat` calls.

  Note that servers don't necessarily send their file system listings in their local time zone. Some use UTC, which actually makes sense because UTC doesn't lead to an ambiguity when there's a switch back from the daylight saving time to the "normal" time of the server location.

  If the time shift value is invalid, for example its absolute value is larger than 24 hours, a `TimeShiftError` is raised.

  Note

  Versions of ftputil before 4.0.0 used a different definition of "time shift", server_time - local_client_time.

  This had the advantage that the default of 0.0 would be correct if the server was set to the same time zone as the client where ftputil runs. On the other hand, this approach meant that the time shift depended on two time zones, not only the one used on the server side. This could be confusing if server and client didn't use the same time zone.

  See also synchronize_times for a way to set the time shift with a simple method call. If you can't use `synchronize_times` and the server uses the same time zone as the client, you can set the time shift value with

      set_time_shift(
        round( (datetime.datetime.now() - datetime.datetime.utcnow()).seconds, -2 )
      )

- `time_shift()`

  returns the currently-set time shift value. See `set_time_shift` above for its definition.

- `synchronize_times()`

  synchronizes the local times of the server and the client, so that upload_if_newer and download_if_newer work as expected, even if the client and the server use different time zones. For this to work, all of the following conditions must be true:

  - The connection between server and client is established.
  - The client has write access to the directory that is current when `synchronize_times` is called.

  If you can't fulfill these conditions, you can nevertheless set the time shift value explicitly with set_time_shift. Trying to call `synchronize_times` if the above conditions aren't met results in a `TimeShiftError` exception.

### Creating and removing directories

- `mkdir(path, [mode])`

  makes the given directory on the remote host. This does not construct "intermediate" directories that don't already exist. The `mode` parameter is ignored; this is for compatibility with `os.mkdir` if an `FTPHost` object is passed into a function instead of the `os` module. See the explanation in the subsection Exception hierarchy.

- `makedirs(path, [mode], exist_ok=False)`

  works similar to `mkdir` (see above), but also makes intermediate directories like `os.makedirs`. The `mode` parameter is only there for compatibility with `os.makedirs` and is ignored.

  `exist_ok` controls whether the existence of any directory but the last in the `path` should be considered an error. If the default `False` is used or passed to `makedirs`, ftputil will raise a `PermanentError` if any directory but the last already exists.

- `rmdir(path)`

  removes the given remote directory. If it's not empty, raise a `PermanentError`.

- `rmtree(path, ignore_errors=False, onerror=None)`

  removes the given remote, possibly non-empty, directory tree. The interface of this method is rather complex, in favor of compatibility with `shutil.rmtree`.

  If `ignore_errors` is set to a true value, errors are ignored. If `ignore_errors` is a false value and `onerror` isn't set, all exceptions occurring during the tree iteration and processing are raised. These exceptions are all of type `PermanentError`.

  To distinguish between different kinds of errors, pass in a callable for `onerror`. This callable must accept three arguments: `func`, `path` and `exc_info`. `func` is a bound method object, for example `your_host_object.listdir`. `path` is the path that was the recent argument of the respective method (`listdir`, `remove`, `rmdir`). `exc_info` is the exception info as it is gotten from `sys.exc_info`.

  The code of `rmtree` is taken from Python's `shutil` module and adapted for `ftputil`.

### Removing files and links

- `remove(path)`

  removes a file or link on the remote host, similar to `os.remove`.

- `unlink(path)`

  is an alias for `remove`.

### Retrieving information about directories, files and links

- `listdir(path)`

  returns a list containing the names of the files and directories in the given path, similar to os.listdir. The special names `.` and `..` are not in the list.

The methods `lstat` and `stat` (and some others) rely on the directory listing format used by the FTP server. When connecting to a host, `FTPHost`'s constructor tries to guess the right format, which succeeds in most cases. However, if you get strange results or `ParserError` exceptions by a mere `lstat` call, please enter a ticket.

If `lstat` or `stat` give wrong modification dates or times, look at the methods that deal with time zone differences (time zone correction).

- `lstat(path)`

  returns an object similar to that from os.lstat. This is a kind of tuple with additional attributes; see the documentation of the `os` module for details.

  The result is derived by parsing the output of a `LIST` command on the server. Therefore, the result from `FTPHost.lstat` can not contain more information than the received text. In particular:

  - User and group ids can only be determined as strings, not as numbers, and that only if the server supplies them. This is usually the case with Unix servers but maybe not for other FTP servers.

  - Values for the time of the last modification may be rough, depending on the information from the server. For timestamps older than a year, this usually means that the precision of the modification timestamp value is not better than a day. For newer files, the information may be accurate to a minute.

    If the time of the last modification is before the epoch (usually 1970-01-01 UTC), set the time of the last modification to 0.0.

  - Links can only be recognized on servers that provide this information in the `LIST` output.

  - Stat attributes that can't be determined at all are set to

      `None`. For example, a line of a directory listing may not contain the date/time of a directory's last modification.

  - There's a special problem with stat'ing the root directory. (Stat'ing things in the root directory is fine though.) In this case, a `RootDirError` is raised. This has to do with the algorithm used by `(l)stat`, and I know of no approach which mends this problem.

  Currently, `ftputil` recognizes the common Unix-style and Microsoft/DOS-style directory formats. If you need to parse output from another server type, please write to the ftputil mailing list. You may consider writing your own parser.

- `stat(path)`

  returns `stat` information also for files which are pointed to by a link. This method follows multiple links until a regular file or directory is found. If an infinite link chain is encountered or the target of the last link in the chain doesn't exist, a `PermanentError` is raised.

  The limitations of the `lstat` method also apply to `stat`.

`FTPHost` objects contain an attribute named `path`, similar to os.path. The following methods can be applied to the remote host with the same semantics as for `os.path`:

    abspath(path)
    basename(path)
    commonprefix(path_list)
    dirname(path)
    exists(path)
    getmtime(path)
    getsize(path)
    isabs(path)
    isdir(path)
    isfile(path)
    islink(path)
    join(path1, path2, ...)
    normcase(path)
    normpath(path)
    split(path)
    splitdrive(path)
    splitext(path)
    walk(path, func, arg)

Like Python's counterparts under os.path, `ftputil`'s `is...` methods return `False` if they can't find the path given by their argument.

### Local caching of file system information

Many of the above methods need access to the remote file system to obtain data on directories and files. To get the most recent data, each call to `lstat`, `stat`, `exists`, `getmtime` etc. would require to fetch a directory listing from the server, which can make the program very slow. This effect is more pronounced for operations which mostly scan the file system rather than transferring file data.

For this reason, `ftputil` by default saves the results from directory listings locally and reuses those results. This reduces network accesses and so speeds up the software a lot. However, since data is more rarely fetched from the server, the risk of obsolete data also increases. This will be discussed below.

Caching can be controlled -- if necessary at all -- via the `stat_cache` object in an `FTPHost`'s namespace. For example, after calling

    ftp_host = ftputil.FTPHost(host, user, password)

the cache can be accessed as `ftp_host.stat_cache`.

While `ftputil` usually manages the cache quite well, there are two possible reasons for modifying cache parameters.

The first is when the number of possible entries is too low. You may notice that when you are processing very large directories and the program becomes much slower than before. It's common for code to read a directory with `listdir` and then process the found directories and files. This can also happen implicitly by a call to `FTPHost.walk`. Since version 2.6 `ftputil` automatically increases the cache size if directories with more entries than the current maximum cache size are to be scanned. Most of the time, this works fine.

However, if you need access to stat data for several directories at the same time, you may need to increase the cache explicitly. This is done by the `resize` method:

    ftp_host.stat_cache.resize(20000)

where the argument is the maximum number of `lstat` results to store (the default is 5000, in versions before 2.6 it was 1000). Note that each path on the server, e. g. "/home/schwa/some_dir", corresponds to a single cache entry. Methods like `exists` or `getmtime` all derive their results from a previously fetched `lstat` result.

The value 5000 above means that the cache will hold at most 5000 entries (unless increased automatically by an explicit or implicit `listdir` call, see above). If more are about to be stored, the entries which haven't been used for the longest time will be deleted to make place for newer entries.

The second possible reason to change the cache parameters is to avoid stale cache data. Caching is so effective because it reduces network accesses. This can also be a disadvantage if the file system data on the remote server changes after a stat result has been retrieved; the client, when looking at the cached stat data, will use obsolete information.

There are two potential ways to get such out-of-date stat data. The first happens when an `FTPHost` instance modifies a file path for which it has a cache entry, e. g. by calling `remove` or `rmdir`. Such changes are handled transparently; the path will be deleted from the cache. A different matter are changes unknown to the `FTPHost` object which inspects its cache. Obviously, for example, these are changes by programs running on the remote host. On the other hand, cache inconsistencies can also occur if two `FTPHost` objects change a file system simultaneously:

    with (
      ftputil.FTPHost(server, user1, password1) as ftp_host1,
      ftputil.FTPHost(server, user1, password1) as ftp_host2
    ):
        stat_result1 = ftp_host1.stat("some_file")
        stat_result2 = ftp_host2.stat("some_file")
        ftp_host2.remove("some_file")
        # `ftp_host1` will still see the obsolete cache entry!
        print(ftp_host1.stat("some_file"))
        # Will raise an exception since an `FTPHost` object
        # knows of its own changes.
        print(ftp_host2.stat("some_file"))

At first sight, it may appear to be a good idea to have a shared cache among several `FTPHost` objects. After some thinking, this turns out to be very error-prone. For example, it won't help with different processes using `ftputil`. So, if you have to deal with concurrent write/read accesses to a server, you have to handle them explicitly.

The most useful tool for this is the `invalidate` method. In the example above, it could be used like this:

    with (
      ftputil.FTPHost(server, user1, password1) as ftp_host1,
      ftputil.FTPHost(server, user1, password1) as ftp_host2
    ):
        stat_result1 = ftp_host1.stat("some_file")
        stat_result2 = ftp_host2.stat("some_file")
        ftp_host2.remove("some_file")
        # Invalidate using an absolute path.
        absolute_path = ftp_host1.path.abspath(
                          ftp_host1.path.join(ftp_host1.getcwd(), "some_file"))
        ftp_host1.stat_cache.invalidate(absolute_path)
        # Will now raise an exception as it should.
        print(ftp_host1.stat("some_file"))
        # Would raise an exception since an `FTPHost` object
        # knows of its own changes, even without `invalidate`.
        print(ftp_host2.stat("some_file"))

The method `invalidate` can be used on any absolute path, be it a directory, a file or a link.

By default, the cache entries (if not replaced by newer ones) are stored for an infinite time. That is, if you start your Python process using `ftputil` and let it run for three days a stat call may still access cache data that old. To avoid this, you can set the `max_age` attribute:

    with ftputil.FTPHost(server, user, password) as ftp_host:
        ftp_host.stat_cache.max_age = 60 * 60  # = 3600 seconds

This sets the maximum age of entries in the cache to an hour. This means any entry older won't be retrieved from the cache but its data instead fetched again from the remote host and then again stored for up to an hour. To reset max_age to the default of unlimited age, i. e. cache entries never expire, use `None` as value.

If you are certain that the cache will be in the way, you can disable and later re-enable it completely with `disable` and `enable`:

    with ftputil.FTPHost(server, user, password) as ftp_host:
        ftp_host.stat_cache.disable()
        ...
        ftp_host.stat_cache.enable()

During that time, the cache won't be used; all data will be fetched from the network. After enabling the cache again, its entries will be the same as when the cache was disabled, that is, entries won't get updated with newer data during this period. Note that even when the cache is disabled, the file system data in the code can become inconsistent:

    with ftputil.FTPHost(server, user, password) as ftp_host:
        ftp_host.stat_cache.disable()
        if ftp_host.path.exists("some_file"):
            mtime = ftp_host.path.getmtime("some_file")

In that case, the file `some_file` may have been removed by another process between the calls to `exists` and `getmtime`!

### Iteration over directories

- `walk(top, topdown=True, onerror=None, followlinks=False)`

  iterates over a directory tree, similar to os.walk. Actually, `FTPHost.walk` uses the code from Python with just the necessary modifications, so see the linked documentation.

- `path.walk(path, func, arg)`

  Similar to `os.path.walk`, the `walk` method in FTPHost.path can be used, though `FTPHost.walk` is probably easier to use.

### Other methods

- `close()`

  closes the connection to the remote host. After this, no more interaction with the FTP server is possible with this `FTPHost` object. Usually you don't need to close an `FTPHost` instance with `close` if you set up the instance in a `with` statement.

- `rename(source, target)`

  renames the source file (or directory) on the FTP server.

- `chmod(path, mode)`

  sets the access mode (permission flags) for the given path. The mode is an integer as returned for the mode by the `stat` and `lstat` methods. Be careful: Usually, mode values are written as octal numbers, for example 0755 to make a directory readable and writable for the owner, but not writable for the group and others. If you want to use such octal values, rely on Python's support for them:

      ftp_host.chmod("some_directory", 0o755)

  Not all FTP servers support the `chmod` command. In case of an exception, how do you know if the path doesn't exist or if the command itself is invalid? If the FTP server complies with RFC 959, it should return a status code 502 if the `SITE CHMOD` command isn't allowed. `ftputil` maps this special error response to a `CommandNotImplementedError` which is derived from `PermanentError`.

  So you need to code like this:

      with ftputil.FTPHost(server, user, password) as ftp_host:
          try:
              ftp_host.chmod("some_file", 0o644)
          except ftputil.error.CommandNotImplementedError:
              # `chmod` not supported
              ...
          except ftputil.error.PermanentError:
              # Possibly a non-existent file
              ...

  Because the `CommandNotImplementedError` is more specific, you have to test for it first.

- `copyfileobj(source, target, length=64*1024)`

  copies the contents from the file-like object `source` to the file-like object `target`. The only difference to `shutil.copyfileobj` is the default buffer size. Note that arbitrary file-like objects can be used as arguments (e. g. local files, remote FTP files).

  However, the interfaces of `source` and `target` have to match; the string type read from `source` must be an accepted string type when written to `target`. For example, if you open `source` in Python 3 as a local text file and `target` as a remote file object in binary mode, the transfer will fail since `source.read` gives unicode strings (`str`) whereas `target.write` only accepts byte strings (`bytes`).

  See File-like objects for the construction and use of remote file-like objects.

- `set_parser(parser)`

  sets a custom parser for FTP directories. Note that you have to pass in a parser instance, not the class.

  An extra section shows how to write own parsers if the default parsers in `ftputil` don't work for you.

- `keep_alive()`

  attempts to keep the connection to the remote server active in order to prevent timeouts from happening. This method is primarily intended to keep the underlying FTP connection of an `FTPHost` object alive while a file is uploaded or downloaded. This will require either an extra thread while the upload or download is in progress or calling `keep_alive` from a callback function.

  The `keep_alive` method won't help if the connection has already timed out. In this case, a `ftputil.error.TemporaryError` is raised.

  If you want to use this method, keep in mind that FTP servers define a timeout for a reason. A timeout prevents running out of server connections because of clients that never disconnect on their own.

  Note that the `keep_alive` method does not affect the "hidden" FTP child connections established by `FTPHost.open` (see section FTPHost instances vs. FTP connections for details). You can't use `keep_alive` to avoid a timeout in a stalling transfer like this:

      with ftputil.FTPHost(server, userid, password) as ftp_host:
          with ftp_host.open("some_remote_file", "rb") as fobj:
              data = fobj.read(100)
              # _Futile_ attempt to avoid file connection timeout.
              for i in range(15):
                  time.sleep(60)
                  ftp_host.keep_alive()
              # Will raise an `ftputil.error.TemporaryError`.
              data += fobj.read()

# File-like objects

## Construction

### Basics

`FTPFile` objects are returned by a call to `FTPHost.open`; never use the `FTPFile` constructor directly.

The APIs for remote file-like objects is modeled after the APIs of the built-in `open` function and its return value.

- `FTPHost.open(path, mode="r", buffering=None, encoding=None, errors=None, newline=None, rest=None)`

  returns a file-like object that refers to the path on the remote host. This path may be absolute or relative to the current directory on the remote host (this directory can be determined with the `getcwd` method). As with local file objects, the default mode is "r", i. e. reading text files. Valid modes are "r", "rb", "w", and "wb".

  If a file is opened in binary mode, you must not specify an encoding. On the other hand, if you open a file in text mode, an encoding is used. By default, this is the return value of `locale.getpreferredencoding`, but you can (and probably should) specify a distinct encoding.

  If you open a file in binary mode, the read and write operations use `bytes` objects. That is, read operations return `bytes` and write operations only accept `bytes`.

  Similarly, text files always work with strings (`str`). Here, read operations return string and write operations only accept strings.

  The arguments `buffering`, `errors` and `newline` have the same semantics as in open.

  If the file is opened in binary mode, you may pass 0 or a positive integer for the `rest` argument. The argument is passed to the underlying FTP session instance (for example an instance of `ftplib.FTP`) to start reading or writing at the given byte offset. For example, if a remote file contains the letters "abcdef" in ASCII encoding, `rest=3` will start reading at "d".

  Warning

  If you pass `rest` values which point after the file, the behavior is undefined and may even differ from one FTP server to another. Therefore, use the `rest` argument only for error recovery in case of interrupted transfers. You need to keep track of the transferred data so that you can provide a valid `rest` argument for a resumed transfer.

`FTPHost.open` can also be used in a `with` statement:

    import ftputil

    with ftputil.FTPHost(...) as ftp_host:
        ...
        with ftp_host.open("new_file", "w", encoding="utf8") as fobj:
            fobj.write("This is some text.")

At the end of the `with` block, the remote file will be closed automatically.

If something goes wrong during the construction of the file or in the body of the `with` statement, the file will be closed as well. Exceptions will be propagated as with `try ... finally`.

## Attributes and methods

The methods

    close()
    read([count])
    readline([count])
    readlines()
    write(data)
    writelines(string_sequence)

and the attribute `closed` have the same semantics as for file objects of a local disk file system. The iterator protocol is supported as well, i. e. you can use a loop to read a file line by line:

    with ftputil.FTPHost(server, user, password) as ftp_host:
        with ftp_host.open("some_file") as input_file:
            for line in input_file:
                # Do something with the line, e. g.
                print(line.strip().replace("ftplib", "ftputil"))

For more on file objects, see the section File objects in the Python Library Reference.

# `FTPHost` instances vs. FTP connections

This section explains why keeping an `FTPHost` instance "alive" without timing out sometimes isn't trivial. If you always finish your FTP operations in time, you don't need to read this section.

The file transfer protocol is a stateful protocol. That means an FTP connection always is in a certain state. Each of these states can only change to certain other states under certain conditions triggered by the client or the server.

One of the consequences is that a single FTP connection can't be used at the same time, say, to transfer data on the FTP data channel and to create a directory on the remote host.

For example, consider this:

    >>> import ftplib
    >>> ftp = ftplib.FTP(server, user, password)
    >>> ftp.pwd()
    '/'
    >>> # Start transfer. `CONTENTS` is a text file on the server.
    >>> socket = ftp.transfercmd("RETR CONTENTS")
    >>> socket
    <socket._socketobject object at 0x7f801a6386e0>
    >>> ftp.pwd()
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
      File "/usr/lib64/python2.7/ftplib.py", line 578, in pwd
        return parse257(resp)
      File "/usr/lib64/python2.7/ftplib.py", line 842, in parse257
        raise error_reply, resp
    ftplib.error_reply: 226-File successfully transferred
    226 0.000 seconds (measured here), 5.60 Mbytes per second
    >>>

Note that `ftp` is a single FTP connection, represented by an `ftplib.FTP` instance, not an `ftputil.FTPHost` instance.

On the other hand, consider this:

    >>> import ftputil
    >>> ftp_host = ftputil.FTPHost(server, user, password)
    >>> ftp_host.getcwd()
    >>> fobj = ftp_host.open("CONTENTS")
    >>> fobj
    <ftputil.file.FTPFile object at 0x7f8019d3aa50>
    >>> ftp_host.getcwd()
    u'/'
    >>> fobj.readline()
    u'Contents of FTP test directory\n'
    >>> fobj.close()
    >>>

To be able to start a file transfer (i. e. open a remote file for reading or writing) and still be able to use other FTP commands, ftputil uses a trick. For every remote file, ftputil creates a new FTP connection, called a child connection in the ftputil source code. (Actually, FTP connections belonging to closed remote files are re-used if they haven't timed out yet.)

In most cases this approach isn't noticeable by code using ftputil. However, the nice abstraction of dealing with a single FTP connection falls apart if one of the child connections times out. For example, if you open a remote file and work only with the initial "main" connection to navigate the file system, the FTP connection for the remote file may eventually time out.

While it's often relatively easy to prevent the "main" connection from timing out it's unfortunately practically impossible to do this for a remote file connection (apart from transferring some data, of course). For this reason, FTPHost.keep_alive affects only the main connection. Child connections may still time out if they're idle for too long.

Some more details:

- A kind of "straightforward" way of keeping the main connection alive would be to call `ftp_host.getcwd()`. However, this doesn't work because ftputil caches the current directory and returns it without actually contacting the server. That's the main reason why there's a `keep_alive` method since it calls `pwd` on the FTP connection (i. e. the session object), which isn't a public attribute.
- Some servers define not only an idle timeout but also a transfer timeout. This means the connection times out unless there's some transfer on the data channel for this connection. So ftputil's `keep_alive` doesn't prevent this timeout, but an `ftp_host.listdir(ftp_host.curdir)` call should do it. However, this transfers the data for the whole directory listing which might take some time if the directory has many entries.

Bottom line: If you can, you should organize your FTP actions so that you finish everything before a timeout happens.

# Writing directory parsers

`ftputil` recognizes the two most widely-used FTP directory formats, Unix and MS style, and adjusts itself automatically. Almost every FTP server uses one of these formats.

However, if your server uses a format which is different from the two provided by `ftputil`, you can plug in a custom parser with a single method call and have `ftputil` use this parser.

For this, you need to write a parser class by inheriting from the class `Parser` in the `ftputil.stat` module. Here's an example:

    import ftputil.error
    import ftputil.stat

    class XyzParser(ftputil.stat.Parser):
        """
        Parse the default format of the FTP server of the XYZ
        corporation.
        """

        def parse_line(self, line, time_shift=0.0):
            """
            Parse a `line` from the directory listing and return a
            corresponding `StatResult` object. If the line can't
            be parsed, raise `ftputil.error.ParserError`.

            The `time_shift` argument can be used to fine-tune the
            parsing of dates and times. See the class
            `ftputil.stat.UnixParser` for an example.
            """
            # Split the `line` argument and examine it further; if
            # something goes wrong, raise an `ftputil.error.ParserError`.
            ...
            # Make a `StatResult` object from the parts above.
            stat_result = ftputil.stat.StatResult(...)
            # `_st_name`, `_st_target` and `_st_mtime_precision` are optional.
            stat_result._st_name = ...
            stat_result._st_target = ...
            stat_result._st_mtime_precision = ...
            return stat_result

        # Define `ignores_line` only if the default in the base class
        # doesn't do enough!
        def ignores_line(self, line):
            """
            Return a true value if the line should be ignored. For
            example, the implementation in the base class handles
            lines like "total 17". On the other hand, if the line
            should be used for stat'ing, return a false value.
            """
            is_total_line = super().ignores_line(line)
            my_test = ...
            return is_total_line or my_test

A `StatResult` object is similar to the value returned by os.stat and is usually built with statements like

    stat_result = StatResult(
                    (st_mode, st_ino, st_dev, st_nlink, st_uid,
                     st_gid, st_size, st_atime, st_mtime, st_ctime))
    stat_result._st_name = ...
    stat_result._st_target = ...
    stat_result._st_mtime_precision = ...

with the arguments of the `StatResult` constructor described in the following table.

Index | Attribute | os.stat type | `StatResult` type | Notes
--- | --- | --- | --- | ---
0 | st_mode | int | int |
1 | st_ino | long | long |
2 | st_dev | long | long |
3 | st_nlink | int | int |
4 | st_uid | int | str | usually only available as string
5 | st_gid | int | str | usually only available as string
6 | st_size | long | long |
7 | st_atime | int/float | float |
8 | st_mtime | int/float | float |
9 | st_ctime | int/float | float |
- | _st_name | - | str | file name without directory part
- | _st_target | - | str | link target (may be absolute or relative)
- | _st_mtime_precision | - | int | `st_mtime` precision in seconds

If you can't extract all the desirable data from a line (for example, the MS format doesn't contain any information about the owner of a file), set the corresponding values in the `StatResult` instance to `None`.

Parser classes can use several helper methods which are defined in the class `Parser`:

- `parse_unix_mode` parses strings like "drwxr-xr-x" and returns an appropriate `st_mode` integer value.
- `parse_unix_time` returns a float number usable for the `st_...time` values by parsing arguments like "Nov"/"23"/"02:33" or "May"/"26"/"2005". Note that the method expects the timestamp string already split at whitespace.
- `parse_ms_time` parses arguments like "10-23-01"/"03:25PM" and returns a float number like from `time.mktime`. Note that the method expects the timestamp string already split at whitespace.

Additionally, there's an attribute `_month_numbers` which maps lowercase three-letter month abbreviations to integers.

For more details, see the two "standard" parsers `UnixParser` and `MSParser` in the module `ftputil/stat.py`.

To actually use the parser, call the method set_parser of the `FTPHost` instance.

If you can't write a parser or don't want to, please ask on the ftputil mailing list. Possibly someone has already written a parser for your server or can help with it.

# FAQ / Tips and tricks

## Where can I get the latest version?

See the download page. Announcements will be sent to the mailing list. Announcements on major updates will also be posted to the Python announcements list.

## Is there a mailing list on `ftputil`?

Yes, please visit https://ftputil.sschwarzer.net/mailinglist to subscribe or read the archives.

Though you can technically post without subscribing first I can't recommend it: The mails from non-subscribers have to be approved by me and because the arriving mails contain lots of spam, I rarely go through these mails.

## I found a bug! What now?

Before reporting a bug, make sure that you already read this manual and tried the latest version of `ftputil`. There the bug might have already been fixed.

Please see https://ftputil.sschwarzer.net/issuetrackernotes for guidelines on entering a bug in `ftputil`'s ticket system. If you are unsure if the behaviour you found is a bug or not, you should write to the ftputil mailing list. Never include confidential information (user id, password, file names, etc.) in the problem report! Be careful!

## Does `ftputil` support TLS?

`ftputil` has no built-in TLS support.

On the other hand, there are two ways to get TLS support with ftputil:

- The `ftplib` library has a class `FTP_TLS` that you can use for the `session_factory` keyword argument in the `FTPHost` constructor. You can't use the class directly though if you need additional setup code in comparison to `ftplib.FTP`, for example calling `prot_p`, to secure the data connection. On the other hand, ftputil.session.session_factory can be used to create a custom session factory.

- If you have other requirements that `session_factory` can't fulfill, you may create your own session factory by inheriting from `ftplib.FTP_TLS`:

      import ftplib

      import ftputil

      class FTPTLSSession(ftplib.FTP_TLS):

          def __init__(self, host, user, password):
              ftplib.FTP_TLS.__init__(self)
              self.connect(host, port)
              self.login(user, password)
              # Set up encrypted data connection.
              self.prot_p()
              ...

      # Note the `session_factory` parameter. Pass the class, not
      # an instance.
      with ftputil.FTPHost(server, user, password,
                           session_factory=FTPTLSSession) as ftp_host:
          # Use `ftp_host` as usual.
          ...

## How do I connect to a non-default port?

By default, an instantiated `FTPHost` object connects on the usual FTP port. If you have to use a different port, refer to the section Session factories.

## How do I set active or passive mode?

Please see the section Session factories.

## How can I debug an FTP connection problem?

You can do this with a session factory. See Session factories.

If you want to change the debug level only temporarily after the connection is established, you can reach the session object as the `_session` attribute of the `FTPHost` instance and call `_session.set_debuglevel`. Note that the `_session` attribute should only be accessed for debugging. Calling arbitrary `ftplib.FTP` methods on the session object may cause bugs!

## Conditional upload/download to/from a server in a different time zone

You may find that `ftputil` uploads or downloads files unnecessarily, or not when it should. Please see the section on time zone correction. It may even be sufficient to call synchronize_times.

## When I use `ftputil`, all I get is a `ParserError` exception

The FTP server you connect to may use a directory format that `ftputil` doesn't understand. You can either write and plug in your own parser or ask on the mailing list for help.

## `isdir`, `isfile` or `islink` incorrectly return `False`

Like Python's counterparts under os.path, `ftputil`'s methods return `False` if they can't find the given path.

Probably you used `listdir` on a directory and called `is...()` on the returned names. But if the argument for `listdir` wasn't the current directory, the paths won't be found and so all `is...()` variants will return `False`.

## I don't find an answer to my problem in this document

Please send an email with your problem report or question to the ftputil mailing list, and we'll see what we can do for you. :-)

# Bugs and limitations

- `ftputil` needs at least Python 3.6 to work.
- Whether `ftputil` "sees" "hidden" directory and file names (i. e. names starting with a dot) depends on the configuration of the FTP server. See Hidden files and directories for details.
- Due to the implementation of `lstat` it can not return a sensible value for the root directory `/` though stat'ing entries in the root directory isn't a problem. If you know an implementation that can do this, please let me know. The root directory is handled appropriately in `FTPHost.path.exists/isfile/isdir/islink`, though.
- In multithreaded programs, you can have each thread use one or more `FTPHost` instances as long as no instance is shared with other threads.
- Currently, it is not possible to continue an interrupted upload or download. Contact me if this causes problems for you.
- There's exactly one cache for `lstat` results for each `FTPHost` object, i. e. there's no sharing of cache results determined by several `FTPHost` objects. See Local caching of file system information for the reasons.

# Files

If not overwritten via installation options, the `ftputil` files reside in the `ftputil` package. There's also documentation in reStructuredText and in HTML format. The locations of these files after installation is system-dependent.

The files `test_*.py` and `scripted_session.py` are for unit-testing. If you only use `ftputil`, i. e. don't modify it, you can delete these files.

# References

- Postel J, Reynolds J. 1985. RFC 959 - File Transfer Protocol (FTP).
- Python Software Foundation. 2020. The Python Standard Library.

# Authors

`ftputil` is written by Stefan Schwarzer <sschwarzer@sschwarzer.net> and contributors (see `doc/contributors.txt`).

The original `lrucache` module was written by Evan Prodromou <evan@prodromou.name>.

Feedback is appreciated. :-)