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A Python Parser

Project description

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Parso is a Python parser that supports error recovery and round-trip parsing for different Python versions (in multiple Python versions). Parso is also able to list multiple syntax errors in your python file.

Parso has been battle-tested by jedi. It was pulled out of jedi to be useful for other projects as well.

Parso consists of a small API to parse Python and analyse the syntax tree.

A simple example:

>>> import parso
>>> module = parso.parse('hello + 1', version="3.6")
>>> expr = module.children[0]
>>> expr
PythonNode(arith_expr, [<Name: hello@1,0>, <Operator: +>, <Number: 1>])
>>> print(expr.get_code())
hello + 1
>>> name = expr.children[0]
>>> name
<Name: hello@1,0>
>>> name.end_pos
(1, 5)
>>> expr.end_pos
(1, 9)

To list multiple issues:

>>> grammar = parso.load_grammar()
>>> module = grammar.parse('foo +\nbar\ncontinue')
>>> error1, error2 = grammar.iter_errors(module)
>>> error1.message
'SyntaxError: invalid syntax'
>>> error2.message
"SyntaxError: 'continue' not properly in loop"



pip install parso


  • There will be better support for refactoring and comments. Stay tuned.

  • There’s a WIP PEP8 validator. It’s however not in a good shape, yet.

Known Issues

  • async/await are already used as keywords in Python3.6.

  • from __future__ import print_function is not ignored.


  • Guido van Rossum (@gvanrossum) for creating the parser generator pgen2 (originally used in lib2to3).

  • Salome Schneider for the extremely awesome parso logo.


0.3.1 (2018-07-09)

  • Bugfixes in the diff parser and keyword-only arguments

0.3.0 (2018-06-30)

  • Rewrote the pgen2 parser generator.

0.2.1 (2018-05-21)

  • A bugfix for the diff parser.

  • Grammar files can now be loaded from a specific path.

0.2.0 (2018-04-15)

  • f-strings are now parsed as a part of the normal Python grammar. This makes it way easier to deal with them.

0.1.1 (2017-11-05)

  • Fixed a few bugs in the caching layer

  • Added support for Python 3.7

0.1.0 (2017-09-04)

  • Pulling the library out of Jedi. Some APIs will definitely change.

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