2016年11月13日 星期日

Python中isinstance用法(判斷數據類型)

Description :

Returns a Boolean stating whether the object is an instance or subclass of another object.

Syntax  :

isinstance (object, classinfo)

object Required. An object instance.
classinfo Required. A class, type or a tuple containing classes, types or other tuples.

isinstance( object, classinfo) Return true if the object argument is an instance of the classinfo argument, or of a (direct or indirect) subclass thereof.
Also return true if classinfo is a type object and object is an object of that type. If object is not a class instance or an object of the given type, the function always returns false.
If classinfo is neither a class object nor a type object, it may be a tuple of class or type objects, or may recursively contain other such tuples (other sequence types are not accepted).
If classinfo is not a class, type, or tuple of classes, types, and such tuples, a TypeError exception is raised. Changed in version 2.2: Support for a tuple of type information was added.

Python可以得到一個對象的類型,利用type函數:

>>>lst = [1, 2, 3]
>>>type(lst)
<type 'list'>

不僅如此,還可以利用isinstance函數,來判斷一個對像是否是一個已知的類型。

isinstance說明如下: isinstance(object, class-or-type-or-tuple) -> bool

Return whether an object is an instance of a class or of a subclass thereof. With a type as second argument, return whether that is the object's type. The form using a tuple, isinstance(x, (A, B, ...)), is a shortcut for isinstance(x, A) or isinstance(x, B) or ... (etc.).

其第一個參數為對象,第二個為類型名或類型名的一個列表。其返回值為布爾型。若對象的類型與參數二的類型相同則返回True。若參數二為一個元組,則若對像類型與元組中類型名之一相同即返回True。

 >>>isinstance(lst, list)
True

 >>>isinstance(lst, (int, str, list))
 True




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