Generate .pyc from Python AST?

Question

How would I generate a .pyc file from a Python AST such that I could import the file from Python?

I've used compile to create a code object, then written the co_code attribute to a file, but when I try to import the file from Python, I get an ImportError: Bad magic number in output.pyc.

evandrix · Accepted Answer · 2012-02-23 22:52:23Z

19

The solution can be adapted from the py_compile module:

import marshal
import py_compile
import time
import ast

codeobject = compile(ast.parse('print "Hello World"'), '<string>', 'exec')

with open('output.pyc', 'wb') as fc:
    fc.write('\0\0\0\0')
    py_compile.wr_long(fc, long(time.time()))
    marshal.dump(codeobject, fc)
    fc.flush()
    fc.seek(0, 0)
    fc.write(py_compile.MAGIC)

edited Feb 23, 2012 at 22:52

evandrix

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answered Dec 25, 2011 at 4:20

exupero

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1 Comment

Matt Graham Over a year ago

This is just what I was looking for. But I found I could just write py_compile.MAGIC first, instead of \0\0\0\0, without having to seek back to the beginning and rewrite those 4 bytes.

Greg Hewgill · Accepted Answer · 2011-12-25 01:55:34Z

2

The compile standard function provides this function for both Python 2.x and Python 3.x. However, you will find that the AST representation between 2.x and 3.x is quite different, so be prepared for that.

answered Dec 25, 2011 at 1:55

Greg Hewgill

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5 Comments

exupero Over a year ago

I take it the co_code attribute on the returned code object is the bytecode I'm looking for?

Greg Hewgill Over a year ago

Quite possibly. The only thing I've done with a code object is pass it to exec or eval, I haven't inspected the bytecode directly.

exupero Over a year ago

I've edited the question to be more specific based on what I learned from this answer.

Greg Hewgill Over a year ago

I believe that a "code object" is only a part of what you might find in a compiled module file. One way to create a compiled module file is to start with Python source code. I've got code that can create source code from an AST, if you're interested.

exupero Over a year ago

Indeed you are correct: there appears to be a great deal of other information.

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