# `apt.progress.base` — Abstract classes for progress reporting

This module provides base classes for progress handlers from which all progress classes should inherit from. Progress reporting classes not inheriting from those classes may not work and are not supported.

When creating a subclass of one of those classes, all overridden methods should call the parent’s method first before doing anything else, because the parent method may have to set some attributes. Subclasses not doing so may not work correctly or may not work at all and are completely unsupported.

## AcquireProgress

class apt.progress.base.AcquireProgress

  A monitor object for downloads controlled by the Acquire class. This base class does nothing and should only be used as a base class to inherit from. Instances of this class can be passed to the constructor of `apt_pkg.Acquire` and the Acquire object then uses it to report its progress.

  This class provides several methods which may be overridden by subclasses to implement progress reporting:

  done(item: apt_pkg.AcquireItemDesc)

    Invoked when an item is successfully and completely fetched.

  fail(item: apt_pkg.AcquireItemDesc)

    Invoked when the process of fetching an item encounters a fatal error like a non existing file or no connection to the server.

  fetch(item: apt_pkg.AcquireItemDesc)

    Invoked when some of the item’s data is fetched. This normally means that the file is being fetched now and e.g. the headers have been retrieved already.

  ims_hit(item: apt_pkg.AcquireItemDesc)

    Invoked when an item is confirmed to be up-to-date. For instance, when an HTTP download is informed that the file on the server was not modified.

  media_change(media: str, drive: str) → bool

    Prompt the user to change the inserted removable media. This function is called whenever a media change is needed to ask the user to insert the needed media.

    The parameter media decribes the name of the media type that should be changed, whereas the parameter drive should be the identifying name of the drive whose media should be changed.

    This method should not return until the user has confirmed to the user interface that the media change is complete. It must return True if the user confirms the media change, or False to cancel it.

  pulse(owner: apt_pkg.Acquire) → bool

    This method gets invoked while the Acquire progress given by the parameter owner is underway. It should display information about the current state. It must return `True` to continue the acquistion or `False` to cancel it. This base implementation always returns `True`.

  start()

    Invoked when the Acquire process starts running.

  stop()

    Invoked when the Acquire process stops running.

  In addition to those methods, this class provides several attributes which are set automatically and represent the fetch progress:

  current_bytes

    The number of bytes fetched.

  current_cps

    The current rate of download, in bytes per second.

  current_items

    The number of items that have been successfully downloaded.

  elapsed_time

    The amount of time that has elapsed since the download started.

  fetched_bytes

    The total number of bytes accounted for by items that were successfully fetched.

  last_bytes

    The number of bytes fetched as of the previous call to pulse(), including local items.

  total_bytes

    The total number of bytes that need to be fetched. This member is inaccurate, as new items might be enqueued while the download is in progress!

  total_items

    The total number of items that need to be fetched. This member is inaccurate, as new items might be enqueued while the download is in progress!

## CdromProgress

class apt.progress.base.CdromProgress

  Base class for reporting the progress of adding a cdrom which could be used with apt_pkg.Cdrom to produce an utility like apt-cdrom.

  Methods defined here:

  ask_cdrom_name() → str

    Ask for the name of the cdrom. This method is called when a CD-ROM is added (e.g. via `apt_pkg.Cdrom.add()`) and no label for the CD-ROM can be found.

    Implementations should request a label from the user (e.g. via `raw_input()`) and return this label from the function. The operation can be cancelled if the function returns `None` instead of a string.

  change_cdrom() → bool

    Ask for the CD-ROM to be changed. This method should return `True` if the CD-ROM has been changed or `False` if the CD-ROM has not been changed and the operation should be cancelled. This base implementation returns `False` and thus cancels the operation.

  update(text: str, current: int)

    Periodically invoked in order to update the interface and give information about the progress of the operation.

    This method has two parameters. The first parameter text defines the text which should be displayed to the user as the progress message. The second parameter current is an integer describing how many steps have been completed already.

  total_steps

    The number of total steps, set automatically by python-apt. It may be used in conjunction with the parameter current of the `update()` method to show how far the operation progressed.

## OpProgress

class apt.progress.base.OpProgress

  OpProgress classes are used for reporting the progress of operations such as opening the cache. It is based on the concept of one operation consisting of a series of sub operations.

  Methods defined here:

  done()

    Called once an operation has been completed.

  update([percent=None])

    Called periodically to update the user interface. This function should use the attributes defined below to display the progress information.

    The optional parameter percent is included for compatibility reasons and may be removed at a later time.

  The following attributes are available and are changed by the classes wanting to emit progress:

  major_change

    An automatically set boolean value describing whether the current call to update is caused by a major change. In this case, the last operation has finished.

  op

    An automatically set string which describes the current operation in an human-readable way.

  percent

    An automatically set float value describing how much of the operation has been completed, in percent.

  subop

    An automatically set string which describes the current sub-operation in an human-readable way.

## InstallProgress

class apt.progress.base.InstallProgress

  InstallProgress classes make it possible to monitor the progress of dpkg and APT and emit information at certain stages. It uses file descriptors to read the status lines from APT/dpkg and parses them and afterwards calls the callback methods.

  Subclasses should override the following methods in order to implement progress reporting:

  conffile(current, new)

    Called when a conffile question from dpkg is detected.

    Note

    This part of the API is semi-stable and may be extended with 2 more parameters before the release of 0.7.100.

  error(pkg, errormsg)

    (Abstract) Called when a error is detected during the install.

  The following method should be overridden to implement progress reporting for dpkg-based runs i.e. calls to `run()` with a filename:

  processing(pkg, stage)

    This method is called just before a processing stage starts. The parameter pkg is the name of the package and the parameter stage is one of the stages listed in the dpkg manual under the status-fd option, i.e. “upgrade”, “install” (both sent before unpacking), “configure”, “trigproc”, “remove”, “purge”.

  dpkg_status_change(pkg: str, status: str)

    This method is called whenever the dpkg status of the package changes. The parameter pkg is the name of the package and the parameter status is one of the status strings used in the status file (`/var/lib/dpkg/status`) and documented in dpkg(1).

  The following methods should be overridden to implement progress reporting for `run()` calls with an `apt_pkg.PackageManager` object as their parameter:

  status_change(pkg, percent, status)

    This method implements progress reporting for package installation by APT and may be extended to dpkg at a later time.

    This method takes two parameters: The parameter percent is a float value describing the overall progress and the parameter status is a string describing the current status in an human-readable manner.

  start_update()

    This method is called before the installation of any package starts.

  finish_update()

    This method is called when all changes have been applied.

  There are also several methods which are fully implemented and should not be overridden by subclasses unless the subclass has very special needs:

  fork() → int

    Fork a child process and return 0 to the child process and the PID of the child to the parent process. This implementation just calls `os.fork()` and returns its value.

  run(obj)

    This method runs install actions. The parameter obj may either be a PackageManager object in which case its do_install() method is called or the path to a deb file.

    If the object is a `apt_pkg.PackageManager`, the functions returns the result of calling its `do_install()` method. Otherwise, the function returns the exit status of dpkg. In both cases, `0` means that there were no problems and `!= 0` means that there were issues.

  update_interface()

    This method is responsible for reading the status from dpkg/APT and calling the correct callback methods. Subclasses should not override this method.

  wait_child()

    This method is responsible for calling `update_interface()` from time to time. It exits once the child has exited. The return value is the full status returned by `os.waitpid()` (not only the return code). Subclasses should not override this method.

  The class also provides several attributes which may be useful:

  percent

    The percentage of completion as it was in the last call to `status_change()`.

  status

    The status string passed in the last call to `status_change()`.

  select_timeout

    Used in `wait_child()` to when calling `select.select()` on dpkg’s/APT’s status descriptor. Subclasses may set their own value if needed.

  statusfd

    A readable `file` object from which the status information from APT or dpkg is read.

  writefd

    A writable `file` object to which dpkg or APT write their status information.