获取Python函数信息的方法

Python的反射机制可以动态获取对象信息以及动态调用对象，本文介绍如何获取对象中的函数注释信息以及参数信息。

定义一个Person类：

class Person():
    def talk(self, name, age, height=None):
        """talk function
        :return:
        """
        print(f"My name is {name}")
        print(f"My age is {age}")
        if height is not None:
            print(f"My height is {height}")

dir() 命令也可以获取函数的属性信息：

person = Person()
print(dir(person))

func = getattr(person, "talk")
print(dir(func))

结果

['__class__', '__delattr__', '__dict__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__module__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', '__weakref__', 'talk']

['__call__', '__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__func__', '__ge__', '__get__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__self__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__']

获取函数注释信息

可以通过 doc 属性来获取注释信息（三引号括起来的注释）：

func = getattr(person, "talk")
print(func.__doc__)

结果

talk function
        :return:

获取函数参数

1、 通过 __code__ 属性读取函数参数信息

>> print(dir(func.__code__))
['__class__', '__delattr__', '__dir__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__', '__gt__', '__hash__', '__init__', '__init_subclass__', '__le__', '__lt__', '__ne__', '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__setattr__', '__sizeof__', '__str__', '__subclasshook__', 'co_argcount', 'co_cellvars', 'co_code', 'co_consts', 'co_filename', 'co_firstlineno', 'co_flags', 'co_freevars', 'co_kwonlyargcount', 'co_lnotab', 'co_name', 'co_names', 'co_nlocals', 'co_stacksize', 'co_varnames']>>

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print("co_name: ", func.__code__.co_name)  # 返回函数名
print("co_argcount: ", func.__code__.co_argcount)  # 返回函数的参数个数
print("co_varnames: ",func.__code__.co_varnames) # 返回函数的参数
print("co_filename: ", func.__code__.co_filename) # 返回文件绝对路径
print("co_consts: ", func.__code__.co_consts)
print("co_firstlineno: ",func.__code__.co_firstlineno) # 返回函数行号
print("co_kwonlyargcount: ",func.__code__.co_kwonlyargcount) # 关键字参数
print("co_nlocals: ",func.__code__.co_nlocals) # 返回局部变量个数

结果

co_name:  talk
co_argcount:  4
co_varnames:  ('self', 'name', 'age', 'height')
co_filename:  D:/ProgramWorkspace/PythonNotes/00-Python-Essentials/demo.py
co_consts:  ('talk function\n        :return:\n        ', 'My name is ', 'My age is ', None, 'My height is ')
co_firstlineno:  44
co_kwonlyargcount:  0
co_nlocals:  4

通过 code.co_varnames 可以获取参数名，参数默认值可以通过如下方式获得：

print(func.__defaults__)

结果

(None,)

2、通过inspect库来读取函数参数信息

除了用__code__ 属性外还可以使用inspect库来读取函数参数，使用getfullargspec和signature方法来读取函数参数：

import inspect

# inspect.getargspec(func) # python2
argspec = inspect.getfullargspec(func)
print(argspec.args)
print(argspec.defaults)
print(argspec.varkw)
sig = inspect.signature(func)
print(sig)

结果

['self', 'name', 'age', 'height']
(None,)
None
(name, age, height=None)

也可以在函数内部使用：

class Person():
    def talk(self, name, age, height=None):
        """talk function
        :return:
        """
        frame = inspect.currentframe()
        args, _, _, values = inspect.getargvalues(frame)
        print(inspect.getframeinfo(frame))
        print(f'function name: {inspect.getframeinfo(frame).function}')
        for i in args:
            print(f"{i} = {values[i]}")

if __name__ == '__main__':
    p = Person()
    p.talk("zhangsan", 18, height=175)        

结果

Traceback(filename='D:/ProgramWorkspace/PythonNotes/00-Python-Essentials/demo.py', lineno=44, function='talk', code_context=['        print(inspect.getframeinfo(frame))\n'], index=0)
function name: talk
self = <__main__.Person object at 0x0000023E4CF17B08>
name = zhangsan
age = 18
height = 175