Developer’s notes

Source code

The source code is currently available on GitHub under the terms and conditions of the Expat license. Fork away!

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You can add checks to this program by writing plugins. Each plugin is a simple function that is called for each line of source code, either physical or logical.

Physical line:

  • Raw line of text from the input file.

Logical line:

  • Multi-line statements converted to a single line.
  • Stripped left and right.
  • Contents of strings replaced with "xxx" of same length.
  • Comments removed.

The check function requests physical or logical lines by the name of the first argument:

def maximum_line_length(physical_line)
def extraneous_whitespace(logical_line)
def blank_lines(logical_line, blank_lines, indent_level, line_number)

The last example above demonstrates how check plugins can request additional information with extra arguments. All attributes of the Checker object are available. Some examples:

  • lines: a list of the raw lines from the input file
  • tokens: the tokens that contribute to this logical line
  • line_number: line number in the input file
  • blank_lines: blank lines before this one
  • indent_char: first indentation character in this file (" " or "\t")
  • indent_level: indentation (with tabs expanded to multiples of 8)
  • previous_indent_level: indentation on previous line
  • previous_logical: previous logical line

The docstring of each check function shall be the relevant part of text from PEP 8. It is printed if the user enables --show-pep8. Several docstrings contain examples directly from the PEP 8 document.

Okay: spam(ham[1], {eggs: 2})
E201: spam( ham[1], {eggs: 2})

These examples are verified automatically when pep8.py is run with the --doctest option. You can add examples for your own check functions. The format is simple: "Okay" or error/warning code followed by colon and space, the rest of the line is example source code. If you put 'r' before the docstring, you can use \n for newline and \t for tab.

Then be sure to pass the tests:

$ python pep8.py --testsuite testsuite
$ python pep8.py --doctest
$ python pep8.py --verbose pep8.py

Changes

1.4.4 (2013-02-24)

  • Report E227 or E228 instead of E225 for whitespace around bitwise, shift or modulo operators. (Issue #166)
  • Change the message for E226 to make clear that it is about arithmetic operators.
  • Fix a false positive E128 for continuation line indentation with tabs.
  • Fix regression with the --diff option. (Issue #169)
  • Fix the TestReport class to print the unexpected warnings and errors.

1.4.3 (2013-02-22)

  • Hide the --doctest and --testsuite options when installed.
  • Fix crash with AST checkers when the syntax is invalid. (Issue #160)
  • Read from standard input if no path is specified.
  • Initiate a graceful shutdown on Control+C.
  • Allow to change the checker_class for the StyleGuide.

1.4.2 (2013-02-10)

  • Support AST checkers provided by third-party applications.
  • Register new checkers with register_check(func_or_cls, codes).
  • Allow to construct a StyleGuide with a custom parser.
  • Accept visual indentation without parenthesis after the if statement. (Issue #151)
  • Fix UnboundLocalError when using # noqa with continued lines. (Issue #158)
  • Re-order the lines for the StandardReport.
  • Expand tabs when checking E12 continuation lines. (Issue #155)
  • Refactor the testing class TestReport and the specific test functions into a separate test module.

1.4.1 (2013-01-18)

  • Allow sphinx.ext.autodoc syntax for comments. (Issue #110)
  • Report E703 instead of E702 for the trailing semicolon. (Issue #117)
  • Honor # noqa in addition to # nopep8. (Issue #149)
  • Expose the OptionParser factory for better extensibility.

1.4 (2012-12-22)

  • Report E226 instead of E225 for optional whitespace around common operators (*, **, /, + and -). This new error code is ignored in the default configuration because PEP 8 recommends to “use your own judgement”. (Issue #96)
  • Lines with a # nopep8 at the end will not issue errors on line length E501 or continuation line indentation E12*. (Issue #27)
  • Fix AssertionError when the source file contains an invalid line ending "\r\r\n". (Issue #119)
  • Read the [pep8] section of tox.ini or setup.cfg if present. (Issue #93 and #141)
  • Add the Sphinx-based documentation, and publish it on http://pep8.readthedocs.org/. (Issue #105)

1.3.4 (2012-12-18)

  • Fix false positive E124 and E128 with comments. (Issue #100)
  • Fix error on stdin when running with bpython. (Issue #101)
  • Fix false positive E401. (Issue #104)
  • Report E231 for nested dictionary in list. (Issue #142)
  • Catch E271 at the beginning of the line. (Issue #133)
  • Fix false positive E126 for multi-line comments. (Issue #138)
  • Fix false positive E221 when operator is preceded by a comma. (Issue #135)
  • Fix --diff failing on one-line hunk. (Issue #137)
  • Fix the --exclude switch for directory paths. (Issue #111)
  • Use - filename to read from standard input. (Issue #128)

1.3.3 (2012-06-27)

  • Fix regression with continuation line checker. (Issue #98)

1.3.2 (2012-06-26)

  • Revert to the previous behaviour for --show-pep8: do not imply --first. (Issue #89)
  • Add E902 for IO errors. (Issue #87)
  • Fix false positive for E121, and missed E124. (Issue #92)
  • Set a sensible default path for config file on Windows. (Issue #95)
  • Allow verbose in the configuration file. (Issue #91)
  • Show the enforced max-line-length in the error message. (Issue #86)

1.3.1 (2012-06-18)

  • Explain which configuration options are expected. Accept and recommend the options names with hyphen instead of underscore. (Issue #82)
  • Do not read the user configuration when used as a module (except if config_file=True is passed to the StyleGuide constructor).
  • Fix wrong or missing cases for the E12 series.
  • Fix cases where E122 was missed. (Issue #81)

1.3 (2012-06-15)

Warning

The internal API is backwards incompatible.

  • Remove global configuration and refactor the library around a StyleGuide class; add the ability to configure various reporters. (Issue #35 and #66)
  • Read user configuration from ~/.config/pep8 and local configuration from ./.pep8. (Issue #22)
  • Fix E502 for backslash embedded in multi-line string. (Issue #68)
  • Fix E225 for Python 3 iterable unpacking (PEP 3132). (Issue #72)
  • Enable the new checkers from the E12 series in the default configuration.
  • Suggest less error-prone alternatives for E712 errors.
  • Rewrite checkers to run faster (E22, E251, E27).
  • Fixed a crash when parsed code is invalid (too many closing brackets).
  • Fix E127 and E128 for continuation line indentation. (Issue #74)
  • New option --format to customize the error format. (Issue #23)
  • New option --diff to check only modified code. The unified diff is read from STDIN. Example: hg diff | pep8 --diff (Issue #39)
  • Correctly report the count of failures and set the exit code to 1 when the --doctest or the --testsuite fails.
  • Correctly detect the encoding in Python 3. (Issue #69)
  • Drop support for Python 2.3, 2.4 and 3.0. (Issue #78)

1.2 (2012-06-01)

  • Add E121 through E128 for continuation line indentation. These checks are disabled by default. If you want to force all checks, use switch --select=E,W. Patch by Sam Vilain. (Issue #64)
  • Add E721 for direct type comparisons. (Issue #47)
  • Add E711 and E712 for comparisons to singletons. (Issue #46)
  • Fix spurious E225 and E701 for function annotations. (Issue #29)
  • Add E502 for explicit line join between brackets.
  • Fix E901 when printing source with --show-source.
  • Report all errors for each checker, instead of reporting only the first occurence for each line.
  • Option --show-pep8 implies --first.

1.1 (2012-05-24)

  • Add E901 for syntax errors. (Issues #63 and #30)
  • Add E271, E272, E273 and E274 for extraneous whitespace around keywords. (Issue #57)
  • Add tox.ini configuration file for tests. (Issue #61)
  • Add .travis.yml configuration file for continuous integration. (Issue #62)

1.0.1 (2012-04-06)

  • Fix inconsistent version numbers.

1.0 (2012-04-04)

  • Fix W602 raise to handle multi-char names. (Issue #53)

0.7.0 (2012-03-26)

  • Now --first prints only the first occurence of each error. The --repeat flag becomes obsolete because it is the default behaviour. (Issue #6)
  • Allow to specify --max-line-length. (Issue #36)
  • Make the shebang more flexible. (Issue #26)
  • Add testsuite to the bundle. (Issue #25)
  • Fixes for Jython. (Issue #49)
  • Add PyPI classifiers. (Issue #43)
  • Fix the --exclude option. (Issue #48)
  • Fix W602, accept raise with 3 arguments. (Issue #34)
  • Correctly select all tests if DEFAULT_IGNORE == ''.

0.6.1 (2010-10-03)

  • Fix inconsistent version numbers. (Issue #21)

0.6.0 (2010-09-19)

  • Test suite reorganized and enhanced in order to check more failures with fewer test files. Read the run_tests docstring for details about the syntax.
  • Fix E225: accept print >>sys.stderr, "..." syntax.
  • Fix E501 for lines containing multibyte encoded characters. (Issue #7)
  • Fix E221, E222, E223, E224 not detected in some cases. (Issue #16)
  • Fix E211 to reject v = dic['a'] ['b']. (Issue #17)
  • Exit code is always 1 if any error or warning is found. (Issue #10)
  • --ignore checks are now really ignored, especially in conjunction with --count. (Issue #8)
  • Blank lines with spaces yield W293 instead of W291: some developers want to ignore this warning and indent the blank lines to paste their code easily in the Python interpreter.
  • Fix E301: do not require a blank line before an indented block. (Issue #14)
  • Fix E203 to accept NumPy slice notation a[0, :]. (Issue #13)
  • Performance improvements.
  • Fix decoding and checking non-UTF8 files in Python 3.
  • Fix E225: reject True+False when running on Python 3.
  • Fix an exception when the line starts with an operator.
  • Allow a new line before closing ), } or ]. (Issue #5)

0.5.0 (2010-02-17)

  • Changed the --count switch to print to sys.stderr and set exit code to 1 if any error or warning is found.
  • E241 and E242 are removed from the standard checks. If you want to include these checks, use switch --select=E,W. (Issue #4)
  • Blank line is not mandatory before the first class method or nested function definition, even if there’s a docstring. (Issue #1)
  • Add the switch --version.
  • Fix decoding errors with Python 3. (Issue #13 [1])
  • Add --select option which is mirror of --ignore.
  • Add checks E261 and E262 for spaces before inline comments.
  • New check W604 warns about deprecated usage of backticks.
  • New check W603 warns about the deprecated operator <>.
  • Performance improvement, due to rewriting of E225.
  • E225 now accepts:
    • no whitespace after unary operator or similar. (Issue #9 [1])
    • lambda function with argument unpacking or keyword defaults.
  • Reserve “2 blank lines” for module-level logical blocks. (E303)
  • Allow multi-line comments. (E302, issue #10 [1])

0.4.2 (2009-10-22)

  • Decorators on classes and class methods are OK now.

0.4 (2009-10-20)

  • Support for all versions of Python from 2.3 to 3.1.
  • New and greatly expanded self tests.
  • Added --count option to print the total number of errors and warnings.
  • Further improvements to the handling of comments and blank lines. (Issue #1 [1] and others changes.)
  • Check all py files in directory when passed a directory (Issue #2 [1]). This also prevents an exception when traversing directories with non *.py files.
  • E231 should allow commas to be followed by ). (Issue #3 [1])
  • Spaces are no longer required around the equals sign for keyword arguments or default parameter values.
[1](1, 2, 3, 4, 5, 6) These issues refer to the previous issue tracker.

0.3.1 (2009-09-14)

  • Fixes for comments: do not count them when checking for blank lines between items.
  • Added setup.py for pypi upload and easy_installability.

0.2 (2007-10-16)

  • Loads of fixes and improvements.

0.1 (2006-10-01)

  • First release.