Compile (but do not run) a Python script

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?

@sukhbir: You're right, but I just realized the answer, and it isn't given in that thread. — asmeurer, Dec 27 '10 at 08:23
@asmeurer: Yes it is, the answer that you posted is in that question. — Falmarri, Dec 27 '10 at 08:26
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. — Lennart Regebro, Dec 27 '10 at 08:44
@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. — asmeurer, Dec 27 '10 at 20:42
Using pylint or pyflakes will find *more* problems than compiling will. — Lennart Regebro, Dec 27 '10 at 20:46
@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. — asmeurer, Dec 28 '10 at 05:07
flake8 (https://github.com/pycqa/flake8/blob/master/docs/source/index.rst) — MIkee, Jul 29 '19 at 17:00

score 400 · Answer 1 · answered Dec 08 '11 at 20:56

400

python -m py_compile script.py

answered Dec 08 '11 at 20:56

Mark Johnson

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` – stealthybox Aug 16 '18 at 20:58
Documentation: https://docs.python.org/3/using/cmdline.html#using-on-cmdline and https://docs.python.org/3/library/py_compile.html (In particular, see the discussion of `main()`.) – Alan Jan 22 '19 at 14:53
This is a great answer, but note there is a similar one `python -m compileall some/dir/` that will recurse unlike `py_compile`. – spagh-eddie Aug 31 '21 at 23:57

score 54 · Accepted Answer · edited Jan 16 '15 at 15:34

54

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

edited Jan 16 '15 at 15:34

Eric Leschinski

answered Dec 27 '10 at 08:23

yurymik

7

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. – erik258 Aug 29 '18 at 19:55

score 17 · Answer 3 · edited May 05 '18 at 12:56

17

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.

edited May 05 '18 at 12:56

chaim

answered Dec 27 '10 at 08:28

pafcu

score 9 · Answer 4 · answered Dec 27 '10 at 08:25

9

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.

answered Dec 27 '10 at 08:25

Greg Hewgill

4 Answers4