如何确定函数(的源代码)是否包含循环? [英] How to find out if (the source code of) a function contains a loop?

问题描述

比方说，我有一堆函数a、b、c、d 和e 我想知道他们是否直接使用循环:

Let's say, I have a bunch of functions a, b, c, d and e and I want to find out if they directly use a loop:

def a():
    for i in range(3):
        print(i**2)

def b():
    i = 0
    while i < 3:
        print(i**2)
        i += 1

def c():
    print("
".join([str(i**2) for i in range(3)]))

def d():
    print("
".join(["0", "1", "4"]))

def e():
    "for"

我想编写一个函数 uses_loop 以便我可以期待这些断言通过:

I want to write a function uses_loop so I can expect these assertions to pass:

assert uses_loop(a) == True
assert uses_loop(b) == True
assert uses_loop(c) == False
assert uses_loop(d) == False
assert uses_loop(e) == False

(我希望 uses_loop(c) 返回 False 因为 c 使用列表推导而不是循环.)

(I expect uses_loop(c) to return False because c uses a list comprehension instead of a loop.)

我无法修改a、b、c、d 和e.因此，我认为可以为此使用 ast 并沿用我从 inspect.getsource 获得的函数代码.但我对任何其他建议持开放态度，这只是它如何运作的一个想法.

I can't modify a, b, c, d and e. So I thought it might be possible to use ast for this and walk along the function's code which I get from inspect.getsource. But I'm open to any other proposals, this was only an idea how it could work.

这是我用 ast 来的:

def uses_loop(function):
    import ast
    import inspect
    nodes = ast.walk(ast.parse(inspect.getsource(function)))
    for node in nodes:
        print(node.__dict__)

推荐答案

您需要检查函数的抽象语法树是否有任何节点是 ast.For 或 ast 的实例.While 或 ast.AsyncFor.您可以使用 ast.walk() 访问 AST 的每个节点

You need to check if the function's Abstract Syntaxt Tree has any nodes that are an instance of ast.For or ast.While or ast.AsyncFor. You can use ast.walk() to visit every node of the AST

import ast
import inspect

def uses_loop(function):
    loop_statements = ast.For, ast.While, ast.AsyncFor

    nodes = ast.walk(ast.parse(inspect.getsource(function)))
    return any(isinstance(node, loop_statements) for node in nodes)

请参阅 ast 文档，async for 是 在 3.5 中添加.

See the documentation for ast, async for was added in 3.5.

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