Detailed introduction to Python's built-in isinstance function

English documentation:

isinstance(object,classinfo)

Returntrueifthe object argument is an instance of the classinfo argument, or of a (direct, indirect or virtual) subclass thereof. If object is not an object of the given type, the function always returns false. If classinfo is a tuple of type objects (or recursively, other such tuples), return true if object is an instance of any of the types. If classinfo is not a type or tuple of types and such tuples, a TypeErrorexceptionis raised.

Description:

1.FunctionThe function is used to determine whether the object is an instance of a type object. The object parameter indicates the object that needs to be checked, and the calssinfo parameter indicates the type object.

　2. If the object parameter is an instance of a classinfo type object (or a direct, indirect, or virtual subclass of a classinfo class object), return True.

>>> isinstance(1,int) True >>> isinstance(1,str) False # 定义3各类：C继承B，B继承A >>> class A: pass >>> class B(A): pass >>> class C(B): pass >>> a = A() >>> b = B() >>> c = C() >>> isinstance(a,A) #直接实例 True >>> isinstance(a,B) False >>> isinstance(b,A) #子类实例 True >>> isinstance(c,A) #孙子类实例 True

　3. If the object parameter is passed in a type object, False will always be returned.

>>> isinstance(str,str) False >>> isinstance(bool,int) False

　4. If the classinfo type object is a tuple composed of multiple type objects, and ifobject objectis an instance of any type object in the tuple, return True, otherwise return False.

>>> isinstance(a,(B,C)) False >>> isinstance(a,(A,B,C)) True

　5. If the classinfo type object is not a type object or a tuple composed of multiple type objects, an error (TypeError) will be reported.

>>> isinstance(a,[A,B,C]) Traceback (most recent call last): File "", line 1, in  isinstance(a,[A,B,C]) TypeError: isinstance() arg 2 must be a type or tuple of types

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