Parse Python file and evaluate selected functions

I have a file that contains several python functions, each with some statements.

def func1():
    codeX...
def func2():
    codeY...

codeX and codeY can be multiple statements. I want to be able to parse the file, find a function by name, then evaluate the code in that function.

With the ast module, I can parse the file, find the FunctionDef objects, and get the list of Stmt objects, but how do I turn this into bytecode that I can pass to eval? Should I use the compile module, or the parser module instead?

Basically, the function defs are just used to create separate blocks of code. I want to be able to grab any block of code given the name and then execute that code in eval (pr开发者_StackOverflow中文版oviding my own local/global scope objects). If there is a better way to do this than what I described that would be helpful too.

Thanks

I want to be able to grab any block of code given the name and then execute that code ... (providing my own local/global scope objects).

A naive solution looks like this. This is based on the assumption that the functions don't all depend on global variables.

from  file_that_contains_several_python_functions import *
Direction = some_value
func1()
func2()
func3()

That should do exactly what you want.

However, if all of your functions rely on global variables -- a design that calls to mind 1970's-era FORTRAN -- then you have to do something slightly more complex.

 from  file_that_contains_several_python_functions import *
 Direction = some_value
 func1( globals() )
 func2( globals() )
 func3( globals() )

And you have to rewrite all of your global-using functions like this.

 def func1( context )
     globals().update( context )
     # Now you have access to all kinds of global variables

This seems ugly because it is. Functions which rely entirely on global variables are not really the best idea.

Using Python 2.6.4:

text = """
def fun1():
    print 'fun1'

def fun2():
    print 'fun2'

"""

import ast
tree = ast.parse(text)
# tree.body[0] contains FunctionDef for fun1, tree.body[1] for fun2

wrapped = ast.Interactive(body=[a.body[1]])
code = compile(wrapped, 'yourfile', 'single')
eval(code)
fun2() # prints 'fun2'

Take a look at grammar in ast doc: http://docs.python.org/library/ast.html#abstract-grammar. Top-level statement must be either Module, Interactive or Expression, so you need to wrap function def in one of those.

If you're using Python 2.6 or later, then the compile() function accepts AST objects in addition to source code.

>>> import ast
>>> a = ast.parse("print('hello world')")
>>> x = compile(a, "(none)", "exec")
>>> eval(x)
hello world

These modules have all been rearranged for Python 3.