python isinstance 判斷各種類型的小細節

1. 基本語法

isinstance(object, classinfo)

Return true if the object argument is an instance of the classinfo argument, or of a (direct, indirect or virtual) subclass thereof. Also return true if classinfo is a type object (new-style class) and object is an object of that type or of a (direct, indirect or virtual) subclass thereof. 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.

 

classinfo 處可以是 a class, type, or tuple of classes and types，

如果是 tuple，則滿足 tuple 中的任何一個即返回 True

2. 字符串的類型判斷。

字符串，分為 str 和 unicode，二者均繼承自 basestring

>>> isinstance(u'3.0', unicode)
True
>>> isinstance('3.0', str)
True
>>> isinstance(u'3.0', str)
False
>>> isinstance(u'3.0', str)
False
>>> isinstance(u'3.0', basestring)
True
>>> isinstance('3.0', basestring)
True

3. 數字的類型判斷

數字分為 int 和 float，暫未發現二者共同的有效父類。

可以用 (int, float) tuple 來判斷是否為數字（int 或 float）

>>> isinstance('3', (int, float))
False
>>> isinstance(3.0, (int, float))
True
>>> isinstance(3, (int, float))
True
>>> isinstance(3.0, float)
True
>>> isinstance(3.0, int)
False
>>> isinstance(3, float)
False
>>> isinstance(3, int)
True