Getting method calls and their arguments from method object

Question

Using pythons inspect module I have isolated a method object, I now need to step through the source code in the method to find calls to certain other methods and get their arguments.

For example, suppose in the following class:

def my_method():
    print('hello')
    foobar('apple', 'pear', 6)
    print('world')
    foobar(1, 2, 3)
    return foobar('a', 'b')

I need to extract a list of arguments passed to foobar():

[('apple', 'pear', 6), (1, 2, 3), ('a', 'b', None)]

It can be assumed all arguments are hard coded and not dynamic.

Given a method object from the inspect package, how can I inspect the method calls in said method?

Attempts

• I've tried using regexes with inspect.getsourcelines(method) but this breaks if the argument syntax changes.
• I've looked into abstract syntax trees with pythons ast module but havn't come to any solution.
• There must be a way to complete this using inspect but again I havn't come to any solution.

Answer 1

This is not perfect but should be a start, I will add a better implementation in a bit:

from ast import parse, Call, walk
import importlib
import inspect

mod = "test"
mod = importlib.import_module(mod)
p = parse(inspect.getsource(mod))

from ast import literal_eval

vals = []
for node in p.body:
    if isinstance(node, FunctionDef) and node.name == "my_method":
        for node in walk(node):
            if isinstance(node,Call) and node.func.id == "foobar":
                vals.append([literal_eval(val) for val in node.args])

print(vals)

[['apple', 'pear', 6], [1, 2, 3], ['a', 'b']]

test.py looks like:

def foobar(a=0, b=0, c=None):
    return a, b, c

def other_method(x,y,z):
    return  x,y,z

def my_method():
    print('hello')
    foobar('apple', 'pear', 6)
    print('world')
    foobar(1, 2, 3)
    for i in range(10):
        if i > 9:
            s = foobar(4, 5, 6)
            print(s)
    return foobar('a', 'b')


def my_method2():
    foobar('orange', 'tomatoe', 6)
    foobar(10, 20, 30)
    for i in range(10):
        if i > 9:
            foobar(40, 50, 60)
    other_method("foo","bar","foobar")
    return foobar('c', 'd')

If you had a mixture of both you would need to combine somehow changing the call after print('world') to foobar(a=1, b=2, c=3)

vals = []
for node in p.body:
    if isinstance(node, FunctionDef) and node.name == "my_method":
        for node in walk(node):
            if isinstance(node, Call) and node.func.id == "foobar":
                kws = node.keywords
                if kws:
                    print("Found keywords",[(kw.arg, literal_eval(kw.value)) for kw in kws])
                else:
                    print([literal_eval(val) for val in node.args])

Output:

[['apple', 'pear', 6], [], ['a', 'b'], [4, 5, 6]]
['apple', 'pear', 6]
('Found keywords', [('a', 1), ('b', 2), ('c', 3)])
['a', 'b']
[4, 5, 6]

Using the ast.Nodevisitor to find all Call objects will return all calls to "foobar" in all functions:

from ast import parse, NodeVisitor, literal_eval
import importlib
import inspect

mod = "test"
mod = importlib.import_module(mod)
p = parse(inspect.getsource(mod))


class FindCall(NodeVisitor):
    def __init__(self, *args):
        if len(args) < 1:
            raise ValueError("Must supply at least ine target function")
        self.result = {arg: []for arg in args}

    def visit_Call(self, node):
        if node.func.id in self.result:
            self.result[node.func.id].append(map(literal_eval, node.args))
        # visit the children
        self.generic_visit(node)



fc = FindCall("foobar")
fc.visit(p)
print(fc.result)

Output:

from pprint import pprint as pp
pp(fc.result)

{'foobar': [['apple', 'pear', 6],
            [1, 2, 3],
            [4, 5, 6],
            ['a', 'b'],
            ['orange', 'tomatoe', 6],
            [10, 20, 30],
            [40, 50, 60],
            ['c', 'd']],
 'other_method': [['foo', 'bar', 'foobar']]}

You can again add a search for kwargs and only search the specific functions.