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定制类

getattr

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# Fib实例虽然能作用于for循环，看起来和list有点像，但是，把它当成list来使用还是不行
class Student(object):
    def __init__(self):
        self.name = 'tan'

    def __getattr__(self, item):
        if item == 'score':
            return 99
        else:
            return '其他'


s = Student()
print(s.name) # tan
print(s.a) # 其他
print(s.score) # 99
复制代码

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# Fib实例虽然能作用于for循环，看起来和list有点像，但是，把它当成list来使用还是不行
class Student(object):
    def __init__(self, name):
        self.name = 'tan'

    def __call__(self, *args, **kwargs):
        print('my name is %s.' % self.name)


s = Student('tan')
s()


# 通过callable()函数，我们就可以判断一个对象是否是“可调用”对象
print(callable(Student('aa')))
print(callable(max))
print(callable([1, 2, 3, 4]))
print(callable(None))
print(callable('str'))
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getitem

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

# Fib实例虽然能作用于for循环，看起来和list有点像，但是，把它当成list来使用还是不行
class Fib(object):
    def __init__(self):
        self.a, self.b = 0,5

    def __iter__(self):
        return self  # 实例本身就是迭代对象，返回自己

    def __next__(self):
        self.a, self.b = self.b, self.a + self.b # 计算下一个值
        if self.a > 1000:
            raise StopIteration()
        return self.a

    # Fib当list处理，需加方法
    def __getitem__(self, item):
        a, b = 1, 1
        for x in range(item):
            a, b = b, a+b
        return a

    def __getitem__(self, n):
        if isinstance(n, int):  # n是索引
            a, b = 1, 1
            for x in range(n):
                a, b = b, a + b
            return a
        if isinstance(n, slice):  # n是切片
            start = n.start
            stop = n.stop
            if start is None:
                start = 0
            a, b = 1, 1
            L = []
            for x in range(stop):
                if x >= start:
                    L.append(a)
                a, b = b, a + b
            return L

print(Fib()[5]) # Fib实例当list处理 报错 TypeError: 'Fib' object is not subscriptable 加__getitem__方法转list
for n in Fib():
    print(n)

print(Fib()[1:5])

# 延伸 __setitem__  __delitem__
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iternext

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class Fib(object):
    def __init__(self):
        self.a, self.b = 0,1

    def __iter__(self):
        return self  # 实例本身就是迭代对象，返回自己

    def __next__(self):
        self.a, self.b = self.b, self.a + self.b # 计算下一个值
        if self.a > 1000:
            raise StopIteration()
        return self.a


for n in Fib():
    print(n)

# a 1 b 1
# a 1 b 2
# a 2 b 3
# a 3 b 5
# a 5 b 8
# a 8 b 13
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repr

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class Student(object):
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return 'Student object (name: %s)' % self.name

    __repr__ = __str__

s = Student('tan')


print(s)  # Student object (name: tan)
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str

#!/usr/bin/env python3
# -*- coding: utf-8 -*-

class Student(object):
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return 'Student object (name: %s)' % self.name

print(Student('tan'))  # 没有__str__ 打印 <__main__.Student object at 0x000001C382494C70> 有str 打印Student object (name: tan)