python之列表和生成器表达式篇

一.协程函数的应用

写一个装饰器用于让协程函数不需要输入再执行一次next()函数

分析: 在装饰器中生成该协程函数的生成器, 并且执行一次next()函数

def firstNext(func):
    def wrapper(*args, **kwargs):
        g = func(*args, **kwargs)
        next(g)
        return g
    return wrapper

@firstNext
def eater(name):
    print("{} start to eat".format(name))
    food_list = []
    while True:
        food = yield food_list
        print("{} eat {}".format(name, food))
        food_list.append(food)

g = eater("egon")
print(g.send("包子"))
print(g.send("炸酱面"))

二.面向过程编程

实现 grep -rl 'python' c:/test 的功能

　　一个函数实现

import os

def search(dir_name, partten):
    g = os.walk(dir_name)
    res = {"",}
    for i in g:
        for j in i[-1]:
            file_path = i[0] + "\\" +j
            with open(file_path) as f:
                for line in f:
                    if partten in line:
                        res.add(file_path)
    for line in res:
        if line:
            print(line)

search("c:\\test", "python")

利用生成器来处理
import os

def firstNext(func):
    def wrapper(*args, **kwargs):
        g = func(*args, **kwargs)
        next(g)
        return g
    return wrapper

@firstNext
def search(target):
    while True:
        dir_name = yield
        g = os.walk(dir_name)
        for i in g:
            for j in i[-1]:
                file_path = i[0] + "\\" +j
                target.send(file_path)

@firstNext
def opener(target):
    while True:
        file_path = yield
        with open(file_path) as f:
            target.send((file_path, f))

@firstNext
def cat(target):
    while True:
        file_path, f = yield
        for line in f:
            target.send((file_path, line))

@firstNext
def grep(partten, target):
    while True:
        file_path, line = yield
        if partten in line:
            target.send(file_path)

@firstNext
def printer():
    while True:
        file_path = yield
        print(file_path)

g = search(opener(cat(grep("python",printer()))))
g.send("c:\\test")

三.列表生成式，生成器表达式

列表生成式的具体形式

列表 = [处理变量形成列表元素 for循环 if判断 for循环2]　　

　　等同于

for循环
    if判断
        for循环
            元素=表达式
　　　　列表.append(元素)

　　生成器表达式是 列表生成式的中括号编程圆括号

　　其中获得的是一个生成器

　　可以通过 list(获得的生成器) 来快速生成一个列表