1. 基本语法
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 处可以是 a class, type, or tuple of classes and types，
如果是 tuple，则满足 tuple 中的任何一个即返回 true
2. 字符串的类型判断。
字符串，分为 str 和 unicode，二者均继承自 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. 数字的类型判断
数字分为 int 和 float，暂未发现二者共同的有效父类。
可以用 (int, float) tuple 来判断是否为数字（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