parso - A Python Parser

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"

Resources

• Testing
• PyPI
• Docs
• Uses semantic versioning

Installation

pip install parso

Future

• 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.

Acknowledgements

• Guido van Rossum (@gvanrossum) for creating the parser generator pgen2 (originally used in lib2to3).
• Salome Schneider for the extremely awesome parso logo.