Compile (but do not run) a Python script [duplicate]

Question

I want to check a script for syntax errors. In both 2.x and 3.x, how can I compile the script without running it?

Aeon

@sukhbir: You're right, but I just realized the answer, and it isn't given in that thread. – Aeon

@asmeurer: Yes it is, the answer that you posted is in that question. – Karachi

Compiling and syntax checking are different things, really. You want to syntax check, The answer is in the other thread. You ask how to compile it, which is a different question, you should really change the topic. – Tautologize

@Lennart: Is there a way to check syntax without compiling? I suppose you could use something like pylint, but in Python compiling is such a fast operation that you might as well do that and make truly sure that everything works. – Aeon

Using pylint or pyflakes will find more problems than compiling will. – Tautologize

@Lennart: Unfortunately, Pylint/Pyflakes currently do not satisfy one of the conditions of my original question, which is that it must run in Python 3. – Aeon

This is true, but also just a matter of time. – Tautologize

flake8 (github.com/pycqa/flake8/blob/master/docs/source/index.rst) – Coadjutrix

Answer 1

py_compile — Compile Python source files

import py_compile
py_compile.compile('my_script.py')

Canvas

Before you use this approach, take a look at Mark Johnson's highly voted answer to make this a command-line execution without additional python. – Apostasy

Answer 2

python -m py_compile script.py

Kendry

You can expand on this with find and xargs to check directories. Here's how to run it on your src/ dir: find src -type f -name '*.py' | xargs -n1 python3 -m py_compile – Petcock

Documentation: docs.python.org/3/using/cmdline.html#using-on-cmdline and docs.python.org/3/library/py_compile.html (In particular, see the discussion of main().) – Rainfall

This is a great answer, but note there is a similar one python -m compileall some/dir/ that will recurse unlike py_compile. – Hamadryad

Answer 3

You can use pylint to find syntax errors as well as more subtle errors, such as accessing undefined variables in some rarely-used conditional branch.

Bartram

Answer 4

One way is to do something like this (for test.py):

python -c "__import__('compiler').parse(open('test.py').read())"

This works for Python 2.x.

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