Running Pylint
**************
Invoking Pylint
===============
Pylint is meant to be called from the command line. The usage is
pylint [options] module_or_package
You should give Pylint the name of a python package or module. Pylint
"will not import" this package or module, though uses Python internals
to locate them and as such is subject to the same rules and
configuration. You should pay attention to your "PYTHONPATH", since it
is a common error to analyze an installed version of a module instead
of the development version.
It is also possible to analyze python files, with a few restrictions.
The thing to keep in mind is that Pylint will try to convert the file
name to a module name, and only be able to process the file if it
succeeds.
pylint mymodule.py
should always work since the current working directory is
automatically added on top of the python path
pylint directory/mymodule.py
will work if "directory" is a python package (i.e. has an __init__.py
file) or if "directory" is in the python path.
For more details on this see the Frequently Asked Questions.
You can also start a thin gui around Pylint (require tkinter) by
typing
pylint-gui
This should open a window where you can enter the name of the package
or module to check, at Pylint messages will be displayed in the user
interface.
It is also possible to call Pylint from an other python program,
thanks to "py_run()" function in "epylint" module, assuming Pylint
options are stored in "pylint_options" string, as:
from pylint import epylint as lint
lint.py_run(pylint_options)
To silently run Pylint on a "module_name.py" module, and get its
standard output and error:
from pylint import epylint as lint
(pylint_stdout, pylint_stderr) = lint.py_run('module_name.py', return_std=True)
Command line options
====================
First of all, we have two basic (but useful) options.
--version
show program's version number and exit
-h, --help
show help about the command line options
Pylint is architectured around several checkers. By default all
checkers are enabled. You can disable a specific checker or some of
its messages or messages categories by specifying "--disable=<id>". If
you want to enable only some checkers or some message ids, first use "
--disable=all" then "--enable=<id>" with <id> being a comma separated
list of checker names and message identifiers. See the list of
available features for a description of provided checkers with their
functionalities. The "--disable" and "--enable" options can be used
with comma separated lists mixing checkers, message ids and categories
like "-d C,W,E0611,design"
It is possible to disable all messages with "--disable=all". This is
useful to enable only a few checkers or a few messages by first
disabling everything, and then re-enabling only what you need.
Each checker has some specific options, which can take either a yes/no
value, an integer, a python regular expression, or a comma separated
list of values (which are generally used to override a regular
expression in special cases). For a full list of options, use "--help"
Specifying all the options suitable for your setup and coding
standards can be tedious, so it is possible to use a configuration
file to specify the default values. You can specify a configuration
file on the command line using the "--rcfile" option. Otherwise,
Pylint searches for a configuration file in the following order and
uses the first one it finds:
1. "pylintrc" in the current working directory
2. If the current working directory is in a Python module, Pylint
searches up the hierarchy of Python modules until it finds a
"pylintrc" file. This allows you to specify coding standards on a
module-by-module basis. Of course, a directory is judged to be a
Python module if it contains an "__init__.py" file.
3. The file named by environment variable "PYLINTRC"
4. if you have a home directory which isn't "/root":
1. ".pylintrc" in your home directory
2. ".config/pylintrc" in your home directory
5. "/etc/pylintrc"
The "--generate-rcfile" option will generate a commented configuration
file on standard output according to the current configuration and
exit. This includes:
* Any configuration file found as explained above
* Options appearing before "--generate-rcfile" on the Pylint command
line
Of course you can also start with the default values and hand tune the
configuration.
Other useful global options include:
--ignore=<file[,file]>
Add <file> (may be a directory) to the black list. It should be a base
name, not a path. Multiple entries can be given, separated by comma.
--persistent=y_or_n
Pickle collected data for later comparisons.
--output-format=<format>
Select output format (text, html, custom).
--msg-template=<template>
Modifiy text output message template.
--list-msgs
Generate pylint's messages.
--full-documentation
Generate pylint's full documentation, in reST format.
Parallel execution
==================
It is possible to speed up the execution of Pylint. If the running
computer has more CPUs than one, then the files to be checked could be
spread on all processors to Pylint sub-processes. This functionality
is exposed via "-j" command line parameter. It takes a number of sub-
processes that should be spawned. If the provided number is 0 then the
number of CPUs will be used. The default number of workers is 1.
Example:
This will spawn 4 parallel Pylint sub-process, where each provided
module will be checked in parallel. Discovered problems by checkers
are not displayed immediately. They are shown just after completing
checking a module.
There are some limitations in running checks in parallel in current
implementation. It is not possible to use custom plugins (i.e. "--
load-plugins" option), nor it is not possible to use initialization
hooks (i.e. "--init-hook" option).