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
