Python的反射機制可以動態獲取對象信息以及動態調用對象，本文介紹如何獲取對象中的函數註釋信息以及參數信息。 定義一個Person類： class Person(): def talk(self, name, age, height=None): """talk function :return: ...
Python的反射機制可以動態獲取對象信息以及動態調用對象，本文介紹如何獲取對象中的函數註釋信息以及參數信息。
定義一個Person類：
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() 命令也可以獲取函數的屬性信息：
person = Person()
print(dir(person))
func = getattr(person, "talk")
print(dir(func))
結果
['__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__']
獲取函數註釋信息
可以通過 doc 屬性來獲取註釋信息（三引號括起來的註釋）：
func = getattr(person, "talk")
print(func.__doc__)
結果
talk function
:return:
獲取函數參數
1、 通過 __code__ 屬性讀取函數參數信息
>> 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) # 返回函數名
print("co_argcount: ", func.__code__.co_argcount) # 返回函數的參數個數
print("co_varnames: ",func.__code__.co_varnames) # 返回函數的參數
print("co_filename: ", func.__code__.co_filename) # 返迴文件絕對路徑
print("co_consts: ", func.__code__.co_consts)
print("co_firstlineno: ",func.__code__.co_firstlineno) # 返回函數行號
print("co_kwonlyargcount: ",func.__code__.co_kwonlyargcount) # 關鍵字參數
print("co_nlocals: ",func.__code__.co_nlocals) # 返回局部變數個數
結果
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
通過 code.co_varnames 可以獲取參數名，參數預設值可以通過如下方式獲得：
print(func.__defaults__)
結果
(None,)
2、通過inspect庫來讀取函數參數信息
除了用__code__ 屬性外還可以使用inspect庫來讀取函數參數，使用getfullargspec和signature方法來讀取函數參數：
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)
結果
['self', 'name', 'age', 'height']
(None,)
None
(name, age, height=None)
也可以在函數內部使用：
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)
結果
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
