1.1 获取对象信息
1.1.1 使用type()判断对象类型
>>> type(123) --基本数据类型判断
<class ‘int‘>
>>> type(‘123‘)
<class ‘str‘>
>>> type(abs) --python内置函数的判断
<class ‘builtin_function_or_method‘>
>>> type(Dog)
<class ‘type‘>
>>> type(Dog()) --自定义类的判断，引自上文中的Dogclass
<class ‘__main__.Dog‘>
>>> type(123) == type(456)
True
>>> type(‘123‘) == type(‘456‘) #可以在if中判断
True
判断对象是否是函数，types模块中的常量
>>> importtypes
>>> def fn():
... pass
...
>>> type(fn) == types.FunctionType
True
>>> type(abs) ==types.BuiltinFunctionType
True
>>> type(lambda x:x) ==types.LambdaType
True
>>> type((x for x in range(10)))== types.GeneratorType
True
1.1.2 使用isinstance()判断继承
>>> class Animal(object):
... pass
...
>>> class Dog(Animal):
... pass
...
>>> class Erha(Dog):
... pass
...
>>> # object -> Animal ->Dog -> Erha 继承关系
... a = Animal() #依次创建对象
>>> b = Dog()
>>> c = Erha()
>>>
>>> isinstance(c,Erha)
True
>>> isinstance(c, Dog)
True
>>> isinstance(c, Animal)
True
>>> isinstance(b, Dog)
True
>>> isinstance(b, Animal)
True
>>> isinstance(b, Erha)
False
能用type（）判断也可以用isinstance判断
>>> isinstance(123, int)
True
>>> isinstance(‘a‘, str)
True
>>> isinstance([1,2, 3], (list, tuple)) --判断一个变量是否是某些类型中的一种
True
>>> isinstance((1, 2, 3), (list,tuple))
True
1.1.3 使用dir()获取对象的属性和方法
>>> dir(‘abc‘) --列出属性和方法
[‘__add__‘, ‘__class__‘, ‘__contains__‘,‘__delattr__‘, ‘__dir__‘, ‘__doc__‘, ‘__eq__‘, ‘__format__‘, ‘__ge__‘,‘__getattribute__‘, ‘__getitem__‘, ‘__getnewargs__‘, ‘__gt__‘, ‘__hash__‘,‘__init__‘, ‘__iter__‘, ‘__le__‘, ‘__len__‘, ‘__lt__‘, ‘__mod__‘, ‘__mul__‘,‘__ne__‘, ‘__new__‘, ‘__reduce__‘, ‘__reduce_ex__‘, ‘__repr__‘, ‘__rmod__‘,‘__rmul__‘, ‘__setattr__‘, ‘__sizeof__‘, ‘__str__‘, ‘__subclasshook__‘,‘capitalize‘, ‘casefold‘, ‘center‘, ‘count‘, ‘encode‘, ‘endswith‘,‘expandtabs‘, ‘find‘, ‘format‘, ‘format_map‘, ‘index‘, ‘isalnum‘, ‘isalpha‘,‘isdecimal‘, ‘isdigit‘, ‘isidentifier‘, ‘islower‘, ‘isnumeric‘, ‘isprintable‘,‘isspace‘, ‘istitle‘, ‘isupper‘, ‘join‘, ‘ljust‘, ‘lower‘, ‘lstrip‘,‘maketrans‘, ‘partition‘, ‘replace‘, ‘rfind‘, ‘rindex‘, ‘rjust‘, ‘rpartition‘,‘rsplit‘, ‘rstrip‘, ‘split‘, ‘splitlines‘, ‘startswith‘, ‘strip‘, ‘swapcase‘,‘title‘, ‘translate‘, ‘upper‘, ‘zfill‘]
配合getattr()、setattr()以及hasattr()，我们可以直接操作一个对象的状态。
>>> class Myobject(object):
... def __init__(self):
... self.x = 9
... def power(self):
... return self.x * self.x
...
>>> obj = Myobject()
>>> hasattr(obj,‘x‘) #有属性‘x‘？
True
>>> obj.x
9
>>> getattr(obj,‘x‘)
9
>>> hasattr(obj, ‘y‘) #有属性‘y‘?
False
>>> setattr(obj,‘y‘, 19) #设置一个y属性为19
>>> getattr(obj, ‘y‘)
19
>>> obj.y
19
>>> hasattr(obj, ‘power‘) #有属性power（方法）?
True
>>> getattr(obj, ‘power‘) #获取属性power
<bound method Myobject.power of<__main__.Myobject object at 0x2af174d0bd68>>
SyntaxError: invalid character inidentifier
>>> getattr(obj, ‘power‘)() #获取属性power值
81
>>> fn = getattr(obj, ‘power‘)
>>> fn()
81
hasattr的经典应用场景
应用上述的Myobject()实例
>>> def readPower(obj):
... if hasattr(obj, ‘power‘):
... return obj.power()
... else:
... return None
...
>>> readPower(Myobject)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 3, in readPower
TypeError: power() missing 1 requiredpositional argument: ‘self‘
>>> Myobject().x
9
>>> Myobject().power()
81
>>> readPower(Myobject())
81