How to construct a callable from a Python code object?

Question

Realize this is a rather obscure question, so I'll explain why I'm looking into this.

A Python jit compiler takes a callable and returns a callable.

This is fine, however - the API I'm currently working with uses a Python code object.

A simplistic answer to this question would be to write a function to execute the code, eg:

def code_to_function(code):
    def fn():
        return eval(code)
    return fn

# example use
code  = compile("1 + 1", '<string>', 'eval')
fn = code_to_function(code)
print(fn())  # --> 2

Which is correct, but in this case the jit (happens to be numba), won't evaluate the actual number crunching parts - which is needed to be useful.

So the question is, how to take a code object which evaluates to a value, and convert/construct a callable from it?

Update, thanks to @jsbueno's answer, here's an example of a simple expression evaluator using numba.

jsbueno · Accepted Answer · 2016-03-17 04:03:37Z

4

from types import FunctionType

new_function = FunctionType(code,  globals[, name[, argdefs[, closure]]])

The remaining parameters above may be taken from the original function you have.

answered Mar 17, 2016 at 4:03

jsbueno

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ideasman42 · Accepted Answer · 2016-03-17 04:06:24Z

0

Edit, @jsbueno answer is better, but this may be a useful alternative, or at least be interesting for Python developers interested in manipulating functions.

This can be done by replacing a functions __code__, attrubute, eg:

def code_to_function(code):
    def fn_dummy():
        return None

    fn_dummy.__code__ = code
    return fn_dummy


# example use
code  = compile("1 + 1", '<string>', 'eval')
fn = code_to_function(code)
print(fn())  # --> 2

answered Mar 17, 2016 at 4:06

ideasman42

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