一文读懂Python中的映射

python中的反射功能是由以下四个内置函数提供：hasattr、getattr、setattr、delattr，改四个函数分别用于对对象内部执行：检查是否含有某成员、获取成员、设置成员、删除成员。

获取成员: getattr

class Foo:
    def __init__(self, name, age):
        self.name = name
        self.age = age
obj = Foo('klvchen', 18)
inp = input('>>>')
v = getattr(obj, inp)
print(v)

运行结果:

>>>name
klvchen

class Foo:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def show(self):
        return "%s-%s" %(self.name, self.age)
obj = Foo('klvchen', 18)
func = getattr(obj, 'show')
print(func)
res = func()
print(res)

运行结果:

<bound method Foo.show of <__main__.Foo object at 0x00000234F6942588>>
klvchen-18

检查是否含有成员: hasattr

class Foo:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def show(self):
        return "%s-%s" %(self.name, self.age)
obj = Foo('klvchen', 18)
print(hasattr(obj, 'name1'))

运行结果:

False

设置成员: setattr

class Foo:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def show(self):
        return "%s-%s" %(self.name, self.age)
obj = Foo('klvchen', 18)
# print(hasattr(obj, 'name1'))
setattr(obj, 'key', 'value')
print(obj.key)

运行结果:

value

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删除成员: delattr

class Foo:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    def show(self):
        return "%s-%s" %(self.name, self.age)
obj = Foo('klvchen', 18)
print(obj.name)
delattr(obj, 'name')
print(obj.name)

运行结果:

klvchen
AttributeError: 'Foo' object has no attribute 'name'

通过字符串的形式操作对象中的成员

class Foo:
    stat = '666'
    def __init__(self, name, age):
        self.name = name
        self.age = age
res = getattr(Foo, 'stat')
print(res)

运行结果:

666

创建两个文件，s1.py 和 s2.py

s2.py 内容如下:

NAME = 'klvchen'
def func():
    return 'func'

s1.py 内容如下:

import s2
res1 = getattr(s2, 'NAME')
print(res1)
res2 = getattr(s2, 'func')
result = res2()
print(result)

运行 s1.py 文件:

klvchen
func

创建两个文件，s1.py 和 s2.py

s2.py 内容如下:

NAME = 'klvchen'
def func():
    return 'cwe'
class Foo:
    def __init__(self):
        self.name = 666

s1.py 内容如下:

import s2
res1 = getattr(s2, 'NAME')
print(res1)
res2 = getattr(s2, 'func')
result = res2()
print(result)
cls = getattr(s2, 'Foo')
print(cls)
obj = cls()
print(obj)
print(obj.name)

运行 s1.py 文件，运行结果：

klvchen
cwe
<class 's2.Foo'>
<s2.Foo object at 0x000001CFCDBB2438>
666

创建两个文件，s1.py 和 s2.py

s2.py 内容如下:

def f1():
    return '首页'
def f2():
    return '新闻'
def f3():
    return '精华'

s1.py 内容如下:

import s2
inp = input('请输入要查看的URL: ')
if hasattr(s2, inp):
    func = getattr(s2, inp)
    result = func()
    print(result)
else:
    print('404')

运行 s1.py 文件，运行结果：

请输入要查看的URL: f1
首页