• 属性访问
• 描述符
• 迭代器
• 生成器
• 模块导入
• 包
• 查询功能

属性访问

'属性'
class C:
    def __getattribute__(self, name):
        print('getattribute')
        return super().__getattribute__(name)
    def __getattr__(self, name):
        print('getattr')
    def __setattr__(self, key, value):
        print('setattr')
        super().__setattr__(key, value)
    def __delattr__(self, item):
        print('delattr')
        super().__delattr__(item)
c = C()
c.x
# getattribute
# getattr
c.x = 1
# setattr
c.x
# getattribute
del c.x
# delattr

class A:
    def __init__(self, name):
        self.name = name
    def __setattr__(self, key, value):
        if key == 'no':
            self.name = 'none'
        else:
            # self.name = value 错误的写法，会无限递归下去
            # 推荐下述写法
            super().__setattr__(key, value)

描述符

class Celsius:
    def __init__(self, value=26.0):
        self.value = float(value)

    def __get__(self, instance, owner):
        return self.value

    def __set__(self, instance, value):
        self.value = float(value)


class Fahrenheit:
    def __get__(self, instance, owner):
        return instance.cel * 1.8 + 32

    def __set__(self, instance, value):
        instance.cel = (float(value) - 32) / 1.8


class Temperature:
    cel = Celsius()
    fah = Fahrenheit()

temp = Temperature()
print(temp.cel)
# 26.0
print(temp.fah)
# 78.80000000000001

定制容器

'不可变容器'
class CountList:
    def __init__(self, *args):
        self.values = [x for x in args]
        # count 保存了数被访问的次数
        self.count = {}.fromkeys(range(len(self.values)), 0)

    def __len__(self):
        return len(self.values)

    def __getitem__(self, index):
        self.count[index] += 1
        return self.values[index]


c1 = CountList(1, 2, 3)
c2 = CountList(4, 5)
print(c1[1])
# 2
print(c2[0])
# 4
print(c1.count)
# {0: 0, 1: 1, 2: 0}
print(c2.count)
# {0: 1, 1: 0}
print(c1[1] + c2[0])
# 6
print(c1.count)
# {0: 0, 1: 2, 2: 0}

迭代器

string = 'abcdef'
it = iter(string)
print(next(it))
# a
print(next(it))
# b

'斐波那契数列'
class Fibs:
    def __init__(self, n=10):
        self.a = 0
        self.b = 1
        self.n = n

    def __iter__(self):
        return self

    def __next__(self):
        self.a, self.b = self.b, self.a + self.b
        if self.a > self.n:
            raise StopIteration
        return self.a

fibs = Fibs(100)
for i in fibs:
    print(i)
# 1
# 1
# 2
# 3
# 5
# 8
# 13
# 21
# 34
# 55
# 89

生成器

def myGen():
    print('生成器被执行')
    yield 1
    yield 2

myG = myGen()
print(next(myG))
# 生成器被执行
# 1
print(next(myG))
# 2
# print(next(myG))
# 报错 StopIteration


def libs():
    a = 0
    b = 1
    while True:
        a, b = b, a + b
        yield a

for i in libs():
    if i > 100:
        break
    print(i, end=' ')
# 1 1 2 3 5 8 13 21 34 55 89


c = {i for i in [1, 1, 2, 3, 4, 4, 5, 1, 3, 6]}
print(c)
# {1, 2, 3, 4, 5, 6}

模块导入

if  __name__ == '__main__' 
我们简单的理解就是： 如果模块是被直接运行的，则代码块被运行，如果模块是被导入的，则代码块不被运行。

fun.py

'fun.py 模块'
def test():
    print('测试方法')

def other():
    print('其他方法')

# __name__ 返回的若是__main__则表示为本模块调用
# 否则为其他模块调用，返回值为被调用的模块名fun
if __name__ == '__main__':
    test()

print(__name__)
other()


# 本模块运行结果：
# 测试方法
# __main__
# 其他方法

另一个模块

import sys

print(sys.path)
# （表示将从以下目录查找模块）
# ['E:\\python\\python37.zip', 'E:\\python']

sys.path.append('E:/pycharm/project')
import fun


# 本模块运行结果：
# ['E:\\python\\python37.zip', 'E:\\python']
# fun
# 其他方法

包

引包引模块

# 包名为bao，模块名为fun
import bao.fun as f

查询功能

import time
print(time.__doc__)
# This module provides various functions to...（等介绍）
print(dir(time))
# ['_STRUCT_TM_ITEMS', '__doc__', '__loader__', '__name__', '__package__', '__spec__', 'altzone', 'asctime', 'clock', 'ctime', 'daylight', 'get_clock_info', 'gmtime', 'localtime', 'mktime', 'monotonic', 'monotonic_ns', 'perf_counter', 'perf_counter_ns', 'process_time', 'process_time_ns', 'sleep', 'strftime', 'strptime', 'struct_time', 'thread_time', 'thread_time_ns', 'time', 'time_ns', 'timezone', 'tzname']
print(time.__name__)
# time