Question

我想知道为什么在函数结束后我无法访问变量：“variable_for_raw_data”。代码是这样的：

def htmlfrom(Website_URL):
    import urllib.request
    response = urllib.request.urlopen(Website_URL)
    variable_for_raw_data =(input("What will this data be saved as: "))
    global variable_for_raw_data
    variable_for_raw_data = response.read()

现在为什么我不能在函数结束后访问变量“variable_for_raw_data”？

注意事项：

Python 3.3 urllib NOT urllib2

Answer 1

看起来你正试图动态创建变量，我想你的代码看起来像这样。

def htmlfrom(website_url):
    import urllib.request
    response = urllib.request.urlopen(website_url)
    variable_for_raw_data =(input("What will this data be saved as: "))
    global variable_for_raw_data
    variable_for_raw_data = response.read()


if __name__ == "__main__":

    htmlfrom("www.stackoverflow.com")

    #html_stackoverflow is never created it is the value
    #of variable_for_raw_data before variable_for_raw_data
    #is overridden by response.read()

    #entering information into input doesn't create a variable
    print(html_stackoverflow)

我将如何做到这一点：

import urllib.request

def htmlfrom(website_url): 
    '''
       docstrings
    '''

    response = urllib.request.urlopen(website_url)
    variable_for_raw_data = response.read()
    return variable_for_raw_data

if __name__ == "__main__":

    file_name = input("What will this data be saved as: ")
    html_from_website = htmlfrom("www.stackoverflow.com")

        with open(file_name, 'w') as f: 
        f.write(html_from_website)

<强>解释

如果你在函数中有你的import语句，它只能访问功能（即其他功能无法访问）

import urllib.request

PEP 8有关于如何在python中命名内容的指南 CamelCase通常保留给类名

def htmlfrom(website_url): 
    '''
        docstring 
    '''

Docstrings通常是一个好主意。

有关正确使用globals的更多信息，请查看此问题。根据我对你的情况的了解，我认为你不需要使用它们。

    response = urllib.request.urlopen(website_url)
    variable_for_raw_data = response.read()
    return variable_for_raw_data

如果你不了解`if name == 'main':，你应该阅读它。

if __name__ == "__main__":

不要忘记使用有意义的变量名而不要覆盖 builtins（即file =“foo.txt”将覆盖内置文件）

    file_name = input("What will this data be saved as: ")
    html_from_website = htmlfrom("www.stackoverflow.com")

您可以详细了解上下文管理器here

    with open(file_name, 'w') as f: 
        f.write(html_from_website)

使用globals()编辑，完全不使用案例。

def htmlfrom(website_url):
    import urllib.request
    response = urllib.request.urlopen(website_url)
    variable_for_raw_data =(input("What will this data be saved as: "))
    globals()[variable_for_raw_data] = response.read()

从函数创建python 3中的全局变量

1 个答案: