使用 Python 在另一个函数中使用一个函数的变量

Question

我有一个下载视频文件的程序这里是完整的，不要担心它是一个简短的程序。

import pafy

def download():
    url = raw_input('Please enter the path to the video\n')
    video = pafy.new(url)
    vid_title = video.title
    best = video.getbest()
    streams = video.streams
    print(vid_title)
    for stream in streams:
        print(stream)
    print'Resolution: ',best.resolution,'\nExtension : ', best.extension
    user_choice = raw_input("Do you want to download this video\ny or n\n")
    if user_choice == 'y':
        print'Your video will downloaded soon'
        filename = best.download(filepath = '/home/mark/new_projects')
        another_download()
    elif user_choice =='n':
        print'You have chosen not to download a video'
        another_download()


def another_download():
    another_choice = raw_input('Would you like to download another video\ny or n\n')
    if another_choice == 'y':
        download()
    else:
        print'Thank for using my program'

download()

我想把它分解成更小的功能。我试过这样做：

def url():
    url = raw_input('Please enter the path to the video\n')
    video = pafy.new(url)
    vid_title = video.title
    best = video.getbest()
    streams = video.streams
    print(vid_title)
    for stream in streams:
        print(stream)
    print'Resolution: ',best.resolution,'\nExtension : ', best.extension

def download():
    user_choice = raw_input("Do you want to download this video\ny or n\n")
    if user_choice == 'y':
        print'Your video will downloaded soon'
        filename = best.download(filepath = '/home/mark/new_projects')
        another_download()
    elif user_choice =='n':
        print'You have chosen not to download a video'
        another_download()

但是当我尝试这个时，我收到一条错误消息，告诉我 best 尚未声明。我不想将 best 声明为全局变量。有没有办法在另一个函数中使用一个函数中的变量？

Answer 1

将一个大函数拆分成多个小函数是一个好习惯，但更紧迫的问题是您应该使用主循环并使您的函数 return 而不是像那样将它们链接起来。

现在下载() -> another_download() -> 下载() -> another_download() -> 下载() -> ...，所以如果用户想要下载 n 个视频，您将有 n * 2 - 1 个函数，直到最后一个完成。

顺便 return 解决了你的问题:

def url():
    ...
    return best 

def download():
    best = url()
    ...

Answer 2

这里有几个选项供您选择。我会尽力把它们排好。

选项 1：假设您首先调用 download()，您可以获得 url() return 您需要的内容并将其存储在 download() 方法的变量中：

def url():
    url = raw_input('Please enter the path to the video\n')
    video = pafy.new(url)
    vid_title = video.title
    best = video.getbest()
    streams = video.streams
    print(vid_title)
    for stream in streams:
        print(stream)
    print'Resolution: ',best.resolution,'\nExtension : ', best.extension
    return best

def download():
    user_choice = raw_input("Do you want to download this video\ny or n\n")
    if user_choice == 'y':
        best = url()
        print'Your video will downloaded soon'
        filename = best.download(filepath = '/home/mark/new_projects')
        another_download()
    elif user_choice =='n':
        print'You have chosen not to download a video'
        another_download()

选项 2：您可以使用全局变量，但我不知道在这种情况下使用它们的后果：

best = None
def url():
    global best
    url = raw_input('Please enter the path to the video\n')
    video = pafy.new(url)
    vid_title = video.title
    best = video.getbest()
    streams = video.streams
    print(vid_title)
    for stream in streams:
        print(stream)
    print'Resolution: ',best.resolution,'\nExtension : ', best.extension

def download():
    global best
    user_choice = raw_input("Do you want to download this video\ny or n\n")
    if user_choice == 'y':
        print'Your video will downloaded soon'
        filename = best.download(filepath = '/home/mark/new_projects')
        another_download()
    elif user_choice =='n':
        print'You have chosen not to download a video'
        another_download()

我认为这些解决方案中的任何一个都能满足您的需求，但在这种特定情况下我会推荐第一个，因为它看起来不像是一个复杂的程序。

使用 Python 在另一个函数中使用一个函数的变量

Use a variable from one function within another function with Python

python

variables

pafy