概要
本人python理論知識遠達不到傳授級別，寫文章主要目的是自我總結(jié)，并不能照顧所有人，請見諒，文章結(jié)尾貼有相關(guān)鏈接可以作為補充
全文分為三個部分裝飾器理論知識、裝飾器應用、裝飾器延申
裝飾器基礎(chǔ)
無參裝飾器
'''假定有一個需求是：打印程序函數(shù)運行順序此案例打印的結(jié)果為： foo1 function is starting foo2 function is starting'''from functools import wrapsdef NoParamDec(func): #函數(shù)在被裝飾器裝時后，其函數(shù)屬性也會改變，wraps作用就是保證被裝飾函數(shù)屬性不變 @wraps(func) def warpper(*args, **kwargs): print('{} function is starting'.format(func.__name__)) return func(*args, **kwargs) return warpper#python黑魔法省略了NoParamDec=NoParamDec(foo1)@NoParamDecdef foo1(): foo2()@NoParamDecdef foo2(): passif __name__ == "__main__": foo1()有參裝飾器
'''假定有一個需求是：檢查函數(shù)參數(shù)的類型，只允許匹配正確的函數(shù)通過程序此案例打印結(jié)果為：('a', 'b', 'c')-----------------------分割線------------------------ERROS!!!!b must be <class 'str'> ERROS!!!!c must be <class 'str'> ('a', 2, ['b', 'd']) '''from functools import wrapsfrom inspect import signaturedef typeAssert(*args, **kwargs): deco_args = args deco_kwargs = kwargs def factor(func): #python標準模塊類，可以用來檢查函數(shù)參數(shù)類型，只允許特定類型通過 sig = signature(func) #將函數(shù)形式參數(shù)和規(guī)定類型進行綁定 check_bind_args = sig.bind_partial(*deco_args, **deco_kwargs).arguments @wraps(func) def wrapper(*args, **kwargs): #將實際參數(shù)值和形式參數(shù)進行綁定 wrapper_bind_args = sig.bind(*args, **kwargs).arguments.items() for name, obj in wrapper_bind_args: #遍歷判斷是否實際參數(shù)值是規(guī)定參數(shù)的實例 if not isinstance(obj, check_bind_args[name]): try: raise TypeError('ERROS!!!!{arg} must be {obj} '.format(**{'arg': name, 'obj': check_bind_args[name]})) except Exception as e: print(e) return func(*args, **kwargs) return wrapper return factor@typeAssert(str, str, str)def inspect_type(a, b, c): return (a, b, c)if __name__ == "__main__": print(inspect_type('a', 'b', 'c')) print('{:-^50}'.format('分割線')) print(inspect_type('a', 2, ['b', 'd']))裝飾器鏈
'''假定有一個需求是：輸入類似代碼：@makebold@makeitalicdef say(): return "Hello"輸出：<b><i>Hello</i></b>'''from functools import wrapsdef html_deco(tag): def decorator(fn): @wraps(fn) def wrapped(*args, **kwargs): return '<{tag}>{fn_result}<{tag}>'.format(**{'tag': tag, 'fn_result': fn(*args, **kwargs)}) return wrapped return decorator@html_deco('b')@html_deco('i')def greet(whom=''): # 等價于 geet=html_deco('b')(html_deco('i)(geet)) return 'Hello' + (' ' + whom) if whom else ''if __name__ == "__main__": print(greet('world')) # -> <b><i>Hello world</i></b>裝飾器進階
property 原理
通常，描述符是具有“綁定行為”的對象屬性，其屬性訪問已經(jīng)被描述符協(xié)議中的方法覆蓋。這些方法是__get__()、__set__()和__delete__()。如果一個對象定義這些方法中的任何一個，它被稱為一個描述符。如果對象定義__get__()和__set__()，則它被認為是數(shù)據(jù)描述符。僅定義__get__()的描述器稱為非數(shù)據(jù)描述符（它們通常用于方法，但是其他用途也是可能的）。
屬性查找優(yōu)先級為：
class Property(object): ''' 內(nèi)部property是用c實現(xiàn)的，這里用python模擬實現(xiàn)property功能 代碼參考官方doc文檔 ''' def __init__(self, fget=None, fset=None, fdel=None, doc=None): self.fget = fget self.fset = fset self.fdel = fdel self.__doc__ = doc def __get__(self, obj, objtype=None): if obj is None: return self if self.fget is None: raise (AttributeError, "unreadable attribute") print('self={},obj={},objtype={}'.format(self,obj,objtype)) return self.fget(obj) def __set__(self, obj, value): if self.fset is None: raise (AttributeError, "can't set attribute") self.fset(obj, value) def __delete__(self, obj): if self.fdel is None: raise (AttributeError, "can't delete attribute") self.fdel(obj) def getter(self, fget): return type(self)(fget, self.fset, self.fdel, self.__doc__) def setter(self, fset): return type(self)(self.fget, fset, self.fdel, self.__doc__) def deleter(self, fdel): return type(self)(self.fget, self.fset, fdel, self.__doc__)class Student( object ): @Property def score( self ): return self._score @score.setter def score( self, val ): if not isinstance( val, int ): raise ValueError( 'score must be an integer!' ) if val > 100 or val < 0: raise ValueError( 'score must between 0 ~ 100!' ) self._score = valif __name__ == "__main__": s = Student() s.score = 60 s.score staticmethod 原理
@staticmethod means: when this method is called, we don't pass an instance of the class to it (as we normally do with methods). This means you can put a function inside a class but you can't access the instance of that class (this is useful when your method does not use the instance).
class StaticMethod(object): "python代碼實現(xiàn)staticmethod原理" def __init__(self, f): self.f = f def __get__(self, obj, objtype=None): return self.fclass E(object): #StaticMethod=StaticMethod(f) @StaticMethod def f( x): return xif __name__ == "__main__": print(E.f('staticMethod Test'))classmethod
@staticmethod means: when this method is called, we don't pass an instance of the class to it (as we normally do with methods). This means you can put a function inside a class but you can't access the instance of that class (this is useful when your method does not use the instance).
class ClassMethod(object): "python代碼實現(xiàn)classmethod原理" def __init__(self, f): self.f = f def __get__(self, obj, klass=None): if klass is None: klass = type(obj) def newfunc(*args): return self.f(klass, *args) return newfunc class E(object): #ClassMethod=ClassMethod(f) @ClassMethod def f(cls,x): return x if __name__ == "__main__": print(E().f('classMethod Test'))
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