pylint(1)

NAME
pylint - python code static checker

SYNOPSIS
pylint [ OPTIONS ] [ <arguments> ]

DESCRIPTION
pylint is a Python source code analyzer which looks for programming errors, helps enforcing a coding standard and sniffs for some code smells (as defined in Martin Fowler's Refactoring book)

Pylint can be seen as another PyChecker since nearly all tests you can do with PyChecker can also be done with Pylint. However, Pylint offers some more features, like checking length of lines of code, checking if variable names are well-formed according to your coding standard, or checking if declared interfaces are truly implemented, and much more.

Additionally, it is possible to write plugins to add your own checks.

Pylint is shipped with "pyreverse" (UML diagram generator) and "symilar" (an independent similarities checker).

OPTIONS

--version
    show program's version number and exit

--help, -h
    show this help message and exit

--long-help
    more verbose help.

MASTER

--rcfile=<file>
    Specify a configuration file.

--init-hook=<code>
    Python code to execute, usually for sys.path manipulation such as pygtk.require().

--errors-only, -E
    In error mode, checkers without error messages are disabled and for others, only the ERROR messages are displayed, and no reports are done by default.

--py3k
    In Python 3 porting mode, all checkers will be disabled and only messages emitted by the porting checker will be displayed.

--verbose, -v
    In verbose mode, extra non-checker-related info will be displayed.

--ignore=<file>[,<file>...]
    Add files or directories to the blacklist. They should be base names, not paths. [default: CVS]

--ignore-patterns=<pattern>[,<pattern>...]
    Add files or directories matching the regex patterns to the blacklist. The regex matches against base names, not paths. [default: none]

--persistent=<y_or_n>
    Pickle collected data for later comparisons. [default: yes]

--load-plugins=<modules>
    List of plugins (as comma separated values of python module names) to load, usually to register additional checkers. [default: none]

--jobs=<n-processes>, -j <n-processes>
    Use multiple processes to speed up Pylint. Specifying 0 will auto-detect the number of processors available to use. [default: 1]

--limit-inference-results=<number-of-results>
    Control the amount of potential inferred values when inferring a single object. This can help the performance when dealing with large functions or complex, nested conditions. [default: 100]

--extension-pkg-whitelist=<pkg[,pkg]>
    A comma-separated list of package or module names from where C extensions may be loaded. Extensions are loading into the active Python interpreter and may run arbitrary code. [default: none]

--suggestion-mode=<yn>
    When enabled, pylint would attempt to guess common misconfiguration and emit user-friendly hints instead of false-positive error messages. [default: yes]

--exit-zero
    Always return a 0 (non-error) status code, even if lint errors are found. This is primarily useful in continuous integration scripts.

--from-stdin
    Interpret the stdin as a python script, whose filename needs to be passed as the module_or_package argument.

COMMANDS

--help-msg=<msg-id>
    Display a help message for the given message id and exit. The value may be a comma separated list of message ids.

--list-msgs
    Generate pylint's messages.

--list-groups
    List pylint's message groups.

--list-conf-levels
    Generate pylint's confidence levels.

--full-documentation
    Generate pylint's full documentation.

--generate-rcfile
    Generate a sample configuration file according to the current configuration. You can put other options before this one to get them in the generated configuration.

MESSAGES CONTROL

--confidence=<levels>
    Only show warnings with the listed confidence levels. Leave empty to show all. Valid levels: HIGH, INFERENCE, INFERENCE_FAILURE, UNDEFINED. [default: none]

--enable=<msg ids>, -e <msg ids>
    Enable the message, report, category or checker with the given id(s). You can either give multiple identifier separated by comma (,) or put this option multiple time (only on the command line, not in the configuration file where it should appear only once). See also the "--disable" option for examples.

--disable=<msg ids>, -d <msg ids>
    Disable the message, report, category or checker with the given id(s). You can either give multiple identifiers separated by comma (,) or put this option multiple times (only on the command line, not in the configuration file where it should appear only once). You can also use "--disable=all" to disable everything first and then reenable specific checks. For example, if you want to run only the similarities checker, you can use "--disable=all --enable=similarities". If you want to run only the classes checker, but have no Warning level messages displayed, use "--disable=all --enable=classes --disable=W".

REPORTS

--output-format=<format>, -f <format>
    Set the output format. Available formats are text, parseable, colorized, json and msvs (visual studio). You can also give a reporter class, e.g. mypackage.mymodule.MyReporterClass. [default: text]

--reports=<y_or_n>, -r <y_or_n>
    Tells whether to display a full report or only the messages. [default: no]

--evaluation=<python_expression>
    Python expression which should return a score less than or equal to 10. You have access to the variables 'error', 'warning', 'refactor', and 'convention' which contain the number of messages in each category, as well as 'statement' which is the total number of statements analyzed. This score is used by the global evaluation report (RP0004). [default: 10.0 - ((float(5 * error + warning + refactor + convention) / statement) * 10)]

--score=<y_or_n>, -s <y_or_n>
    Activate the evaluation score. [default: yes]

--msg-template=<template>
    Template used to display messages. This is a python new-style format string used to format the message information. See doc for all details.

TYPECHECK

--ignore-on-opaque-inference=<y_or_n>
    This flag controls whether pylint should warn about no-member and similar checks whenever an opaque object is returned when inferring. The inference can return multiple potential results while evaluating a Python object, but some branches might not be evaluated, which results in partial inference. In that case, it might be useful to still emit no-member and other checks for the rest of the inferred objects. [default: yes]

--ignore-mixin-members=<y_or_n>
    Tells whether missing members accessed in mixin class should be ignored. A mixin class is detected if its name ends with "mixin" (case insensitive). [default: yes]

--ignore-none=<y_or_n>
    Tells whether to warn about missing members when the owner of the attribute is inferred to be None. [default: yes]

--ignored-modules=<module names>
    List of module names for which member attributes should not be checked (useful for modules/projects where namespaces are manipulated during runtime and thus existing member attributes cannot be deduced by static analysis). It supports qualified module names, as well as Unix pattern matching. [default: none]

--ignored-classes=<members names>
    List of class names for which member attributes should not be checked (useful for classes with dynamically set attributes). This supports the use of qualified names. [default: optparse.Values,thread._local,_thread._local]

--generated-members=<members names>
    List of members which are set dynamically and missed by pylint inference system, and so shouldn't trigger E1101 when accessed. Python regular expressions are accepted. [default: none]

--contextmanager-decorators=<decorator names>
    List of decorators that produce context managers, such as contextlib.contextmanager. Add to this list to register other decorators that produce valid context managers. [default: contextlib.contextmanager]

--missing-member-hint-distance=<member hint edit distance>
    The minimum edit distance a name should have in order to be considered a similar match for a missing member name. [default: 1]

--missing-member-max-choices=<member hint max choices>
    The total number of similar names that should be taken in consideration when showing a hint for a missing member. [default: 1]

--missing-member-hint=<missing member hint>
    Show a hint with possible names when a member name was not found. The aspect of finding the hint is based on edit distance. [default: yes]

--signature-mutators=<decorator names>
    List of decorators that change the signature of a decorated function. [default: none]

LOGGING

--logging-modules=<comma separated list>
    Logging modules to check that the string format arguments are in logging function parameter format. [default: logging]

--logging-format-style=<old (%) or new ({)>
    Format style used to check logging format string. `old` means using % formatting, while `new` is for `{}` formatting. [default: old]

EXCEPTIONS

--overgeneral-exceptions=<comma-separated class names>
    Exceptions that will emit a warning when being caught. Defaults to "BaseException, Exception". [default: BaseException,Exception]

SIMILARITIES

--min-similarity-lines=<int>
    Minimum lines number of a similarity. [default: 4]

--ignore-comments=<y or n>
    Ignore comments when computing similarities. [default: yes]

--ignore-docstrings=<y or n>
    Ignore docstrings when computing similarities. [default: yes]

--ignore-imports=<y or n>
    Ignore imports when computing similarities. [default: no]

IMPORTS

--deprecated-modules=<modules>
    Deprecated modules which should not be used, separated by a comma. [default: optparse,tkinter.tix]

--preferred-modules=<module:preferred-module>
    Couples of modules and preferred modules, separated by a comma. [default: none]

--import-graph=<file.dot>
    Create a graph of every (i.e. internal and external) dependencies in the given file (report RP0402 must not be disabled). [default: none]

--ext-import-graph=<file.dot>
    Create a graph of external dependencies in the given file (report RP0402 must not be disabled). [default: none]

--int-import-graph=<file.dot>
    Create a graph of internal dependencies in the given file (report RP0402 must not be disabled). [default: none]

--known-standard-library=<modules>
    Force import order to recognize a module as part of the standard compatibility libraries. [default: none]

--known-third-party=<modules>
    Force import order to recognize a module as part of a third party library. [default: enchant]

--analyse-fallback-blocks=<y_or_n>
    Analyse import fallback blocks. This can be used to support both Python 2 and 3 compatible code, which means that the block might have code that exists only in one or another interpreter, leading to false positives when analysed. [default: no]

--allow-wildcard-with-all=<y_or_n>
    Allow wildcard imports from modules that define __all__. [default: no]

VARIABLES

--init-import=<y_or_n>
    Tells whether we should check for unused import in __init__ files. [default: no]

--dummy-variables-rgx=<regexp>
    A regular expression matching the name of dummy variables (i.e. expected to not be used). [default: _+$|(_[a-zA-Z0-9_]*[a-zA-Z0-9]+?$)|dummy|^ignored_|^unused_]

--additional-builtins=<comma separated list>
    List of additional names supposed to be defined in builtins. Remember that you should avoid defining new builtins when possible. [default: none]

--callbacks=<callbacks>
    List of strings which can identify a callback function by name. A callback name must start or end with one of those strings. [default: cb_,_cb]

--redefining-builtins-modules=<comma separated list>
    List of qualified module names which can have objects that can redefine builtins. [default: six.moves,past.builtins,future.builtins,builtins,io]

--ignored-argument-names=<regexp>
    Argument names that match this expression will be ignored. Default to name with leading underscore. [default: _.*|^ignored_|^unused_]

--allow-global-unused-variables=<y_or_n>
    Tells whether unused global variables should be treated as a violation. [default: yes]

CLASSES

--defining-attr-methods=<method names>
    List of method names used to declare (i.e. assign) instance attributes. [default: __init__,__new__,setUp]

--valid-classmethod-first-arg=<argument names>
    List of valid names for the first argument in a class method. [default: cls]

--valid-metaclass-classmethod-first-arg=<argument names>
    List of valid names for the first argument in a metaclass class method. [default: cls]

--exclude-protected=<protected access exclusions>
    List of member names, which should be excluded from the protected access warning. [default: _asdict,_fields,_replace,_source,_make]

SPELLING

--spelling-dict=<dict name>
    Spelling dictionary name. Available dictionaries: none. To make it work, install the python-enchant package. [default: none]

--spelling-ignore-words=<comma separated words>
    List of comma separated words that should not be checked. [default: none]

--spelling-private-dict-file=<path to file>
    A path to a file that contains the private dictionary; one word per line. [default: none]

--spelling-store-unknown-words=<y_or_n>
    Tells whether to store unknown words to the private dictionary (see the --spelling-private-dict-file option) instead of raising a message. [default: no]

--max-spelling-suggestions=N
    Limits count of emitted suggestions for spelling mistakes. [default: 4]

FORMAT

--max-line-length=<int>
    Maximum number of characters on a single line. [default: 100]

--ignore-long-lines=<regexp>
    Regexp for a line that is allowed to be longer than the limit. [default: ^\s*(# )?<?https?://\S+>?$]

--single-line-if-stmt=<y_or_n>
    Allow the body of an if to be on the same line as the test if there is no else. [default: no]

--single-line-class-stmt=<y_or_n>
    Allow the body of a class to be on the same line as the declaration if body contains single statement. [default: no]

--no-space-check=trailing-comma,dict-separator,empty-line
    List of optional constructs for which whitespace checking is disabled. `dict-separator` is used to allow tabulation in dicts, etc.: {1 : 1,\n222: 2}. `trailing-comma` allows a space between comma and closing bracket: (a, ). `empty-line` allows space-only lines. [default: trailing-comma,dict-separator]

--max-module-lines=<int>
    Maximum number of lines in a module. [default: 1000]

--indent-string=<string>
    String used as indentation unit. This is usually " " (4 spaces) or "\t" (1 tab). [default: ' ']

--indent-after-paren=<int>
    Number of spaces of indent required inside a hanging or continued line. [default: 4]

--expected-line-ending-format=<empty or LF or CRLF>
    Expected format of line ending, e.g. empty (any line ending), LF or CRLF. [default: none]

BASIC

--good-names=<names>
    Good variable names which should always be accepted, separated by a comma. [default: i,j,k,ex,Run,_]

--bad-names=<names>
    Bad variable names which should always be refused, separated by a comma. [default: foo,bar,baz,toto,tutu,tata]

--name-group=<name1:name2>
    Colon-delimited sets of names that determine each other's naming style when the name regexes allow several styles. [default: none]

--include-naming-hint=<y_or_n>
    Include a hint for the correct naming format with invalid-name. [default: no]

--property-classes=<decorator names>
    List of decorators that produce properties, such as abc.abstractproperty. Add to this list to register other decorators that produce valid properties. These decorators are taken in consideration only for invalid-name. [default: abc.abstractproperty]

--argument-naming-style=<style>
    Naming style matching correct argument names. [default: snake_case]

--argument-rgx=<regexp>
    Regular expression matching correct argument names. Overrides argument-naming-style.

--attr-naming-style=<style>
    Naming style matching correct attribute names. [default: snake_case]

--attr-rgx=<regexp>
    Regular expression matching correct attribute names. Overrides attr-naming-style.

--class-naming-style=<style>
    Naming style matching correct class names. [default: PascalCase]

--class-rgx=<regexp>
    Regular expression matching correct class names. Overrides class-naming-style.

--class-attribute-naming-style=<style>
    Naming style matching correct class attribute names. [default: any]

--class-attribute-rgx=<regexp>
    Regular expression matching correct class attribute names. Overrides class-attribute-naming-style.

--const-naming-style=<style>
    Naming style matching correct constant names. [default: UPPER_CASE]

--const-rgx=<regexp>
    Regular expression matching correct constant names. Overrides const-naming-style.

--function-naming-style=<style>
    Naming style matching correct function names. [default: snake_case]

--function-rgx=<regexp>
    Regular expression matching correct function names. Overrides function-naming-style.

--inlinevar-naming-style=<style>
    Naming style matching correct inline iteration names. [default: any]

--inlinevar-rgx=<regexp>
    Regular expression matching correct inline iteration names. Overrides inlinevar-naming-style.

--method-naming-style=<style>
    Naming style matching correct method names. [default: snake_case]

--method-rgx=<regexp>
    Regular expression matching correct method names. Overrides method-naming-style.

--module-naming-style=<style>
    Naming style matching correct module names. [default: snake_case]

--module-rgx=<regexp>
    Regular expression matching correct module names. Overrides module-naming-style.

--variable-naming-style=<style>
    Naming style matching correct variable names. [default: snake_case]

--variable-rgx=<regexp>
    Regular expression matching correct variable names. Overrides variable-naming-style.

--no-docstring-rgx=<regexp>
    Regular expression which should only match function or class names that do not require a docstring. [default: ^_]

--docstring-min-length=<int>
    Minimum line length for functions/classes that require docstrings, shorter ones are exempt. [default: -1]

MISCELLANEOUS

--notes=<comma separated values>
    List of note tags to take in consideration, separated by a comma. [default: FIXME,XXX,TODO]

DESIGN

--max-args=<int>
    Maximum number of arguments for function / method. [default: 5]

--max-locals=<int>
    Maximum number of locals for function / method body. [default: 15]

--max-returns=<int>
    Maximum number of return / yield for function / method body. [default: 6]

--max-branches=<int>
    Maximum number of branch for function / method body. [default: 12]

--max-statements=<int>
    Maximum number of statements in function / method body. [default: 50]

--max-parents=<num>
    Maximum number of parents for a class (see R0901). [default: 7]

--max-attributes=<num>
    Maximum number of attributes for a class (see R0902). [default: 7]

--min-public-methods=<num>
    Minimum number of public methods for a class (see R0903). [default: 2]

--max-public-methods=<num>
    Maximum number of public methods for a class (see R0904). [default: 20]

--max-bool-expr=<num>
    Maximum number of boolean expressions in an if statement (see R0916). [default: 5]

REFACTORING

--max-nested-blocks=<int>
    Maximum number of nested blocks for function / method body [default: 5]

--never-returning-functions=NEVER_RETURNING_FUNCTIONS
    Complete name of functions that never returns. When checking for inconsistent-return-statements if a never returning function is called then it will be considered as an explicit return statement and no message will be printed. [default: sys.exit]

STRING

--check-str-concat-over-line-jumps=<y_or_n>
    This flag controls whether the implicit-str-concat-in-sequence should generate a warning on implicit string concatenation in sequences defined over several lines. [default: no]

ENVIRONMENT VARIABLES

The following environment variables are used:
    * PYLINTHOME
    Path to the directory where persistent data for the run will be stored. If not found, it defaults to ~/.pylint.d/ or .pylint.d (in the current working directory).
    * PYLINTRC
    Path to the configuration file. See the documentation for the method used to search for configuration file.

OUTPUT
Using the default text output, the message format is :

        MESSAGE_TYPE: LINE_NUM:[OBJECT:] MESSAGE

There are 5 kind of message types :
    * (C) convention, for programming standard violation
    * (R) refactor, for bad code smell
    * (W) warning, for python specific problems
    * (E) error, for probable bugs in the code
    * (F) fatal, if an error occurred which prevented pylint from doing further processing.

OUTPUT STATUS CODE
Pylint should leave with following status code:
    * 0 if everything went fine
    * 1 if a fatal message was issued
    * 2 if an error message was issued
    * 4 if a warning message was issued
    * 8 if a refactor message was issued
    * 16 if a convention message was issued
    * 32 on usage error

status 1 to 16 will be bit-ORed so you can know which different categories has been issued by analysing pylint output status code

SEE ALSO
/usr/share/doc/pythonX.Y-pylint/

BUGS
Please report bugs on the project's mailing list: mailto:code-quality@python.org

AUTHOR
Python Code Quality Authority <code-quality@python.org>