Pylint output

Output options

Output by default is written to stdout. The simplest way to output to a file is with the --output=<filename> option.

The default format for the output is raw text. You can change this by passing pylint the --output-format=<value> option. Possible values are: text, json, parseable, colorized and msvs (for Visual Studio).

Multiple output formats can be used at the same time by passing a comma-separated list of formats to --output-format. This output can be redirected to a file by giving a filename after a colon.

For example, to save a json report to somefile.json and print a colorized report to stdout at the same time:

--output-format=json:somefile.json,colorized

Finally, it is possible to invoke pylint programmatically with a reporter initialized with a custom stream:

pylint_output = StringIO() # Custom open stream
reporter = text.TextReporter(pylint_output)
Run(["test_file.py"], reporter=reporter, do_exit=False)
print(pylint_output.getvalue()) # Retrieve and print the text report

The reporter can accept any stream object as as parameter. In this example, the stream outputs to a file:

with open("report.out", "w") as f:
  reporter = text.TextReporter(f)
  Run(["test_file.py"], reporter=reporter, do_exit=False)

This would be useful to capture pylint output in an open stream which can be passed onto another program.

Custom message formats

You can customize the exact way information are displayed using the --msg-template=<format string> option. The format string uses the Python new format syntax and the following fields are available :

path

relative path to the file

abspath

absolute path to the file

line

line number

column

column number

end_line

line number of the end of the node

end_column

column number of the end of the node

module

module name

obj

object within the module (if any)

msg

text of the message

msg_id

the message code (eg. I0011)

symbol

symbolic name of the message (eg. locally-disabled)

C

one letter indication of the message category

category

fullname of the message category

For example, the former (pre 1.0) default format can be obtained with:

pylint --msg-template='{msg_id}:{line:3d},{column}: {obj}: {msg}'

A few other examples:

  • the default format:

    {path}:{line}:{column}: {msg_id}: {msg} ({symbol})

  • Visual Studio compatible format (former 'msvs' output format):

    {path}({line}): [{msg_id}{obj}] {msg}

  • Parseable (Emacs and all, former 'parseable' output format) format:

    {path}:{line}: [{msg_id}({symbol}), {obj}] {msg}

The --msg-template option can only be combined with text-based reporters (--output-format either unspecified or one of: parseable, colorized or msvs). If both --output-format and --msg-template are specified, the --msg-template option will take precedence over the default line format defined by the reporter class.

If end_line or end_column are None, they will be represented as an empty string by the default TextReporter.

Source code analysis section

For each python module, Pylint will first display a few '*' characters followed by the name of the module. Then, a number of messages with the following format:

MESSAGE_TYPE: LINE_NUM:[OBJECT:] MESSAGE

You can get another output format, useful since it's recognized by most editors or other development tools using the --output-format=parseable option.

The message type can be:

  • [I]nformational messages that Pylint emits (do not contribute to your analysis score)

  • [R]efactor for a "good practice" metric violation

  • [C]onvention for coding standard violation

  • [W]arning for stylistic problems, or minor programming issues

  • [E]rror for important programming issues (i.e. most probably bug)

  • [F]atal for errors which prevented further processing

Sometimes the line of code which caused the error is displayed with a caret pointing to the error. This may be generalized in future versions of Pylint.

Example (extracted from a run of Pylint on itself...):

************* Module pylint.checkers.format
W: 50: Too long line (86/80)
W:108: Operator not followed by a space
     print >>sys.stderr, 'Unable to match %r', line
            ^
W:141: Too long line (81/80)
W: 74:searchall: Unreachable code
W:171:FormatChecker.process_tokens: Redefining built-in (type)
W:150:FormatChecker.process_tokens: Too many local variables (20/15)
W:150:FormatChecker.process_tokens: Too many branches (13/12)

Reports section

Following the analysis message, Pylint can display a set of reports, each one focusing on a particular aspect of the project, such as number of messages by categories, modules dependencies. These features can be enabled through the --reports=y option, or its shorthand version -rn.

For instance, the metrics report displays summaries gathered from the current run.

  • the number of processed modules

  • for each module, the percentage of errors and warnings

  • the total number of errors and warnings

  • percentage of classes, functions and modules with docstrings, and a comparison from the previous run

  • percentage of classes, functions and modules with correct name (according to the coding standard), and a comparison from the previous run

  • a list of external dependencies found in the code, and where they appear

Score section

Finally, Pylint displays a global evaluation score for the code, rated out of a maximum score of 10.0. This output can be suppressed through the --score=n option, or its shorthand version -sn.

The evaluation formula can be overridden with the --evaluation=<python_expression> option.