Creating global variable in python 3 from functions

Question

I was wondering why I can't access the variable: "variable_for_raw_data" after the function ends. The code is like this:

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()

Now why can't I access the variable "variable_for_raw_data" after the functions ends?

Things to note:

Python 3.3 urllib NOT urllib2

You should be able to access it. Show us the code where you try to access it. — Ned Batchelder
– Ned Batchelder, Commented Mar 21, 2013 at 16:14
htmlfrom("stackoverflow.com/questions/15552601/…) What will this data be saved as: html_stackoverflow >>> print(html_stackoverflow) Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> print(html_stackoverflow) NameError: name 'html_stackoverflow' is not defined — user2070615
– user2070615, Commented Mar 21, 2013 at 16:17
You can see I attempted to print(thevariablename) and I got the error: Traceback (most recent call last): File "<pyshell#1>", line 1, in <module> print(html_stackoverflow) NameError: name 'html_stackoverflow' is not defined — user2070615
– user2070615, Commented Mar 21, 2013 at 16:19
Hmm, can you make one paste in the original post, with the same variable names? You're switching the names, so it's not clear what's going on. Unless the problem is that the function creates variable_for_raw_data, and you are trying to access html_stackoverflow. — Ned Batchelder
– Ned Batchelder, Commented Mar 21, 2013 at 16:30
Yes. I feel very stupid. I was trying to access the wrong variable!!! — user2070615
– user2070615, Commented Mar 21, 2013 at 16:36

Community · Accepted Answer · 2017-05-23 12:28:52Z

1

It looks like you're trying to dynamically create variables, I would imagine that your code looks something like this.

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)

Here's how I would do it:

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)

Explanation

if you have your import statement inside the function it is only accessable inside the function (i.e. other functions can't access it)

import urllib.request

PEP 8 has guidelines on how things should be named in python CamelCase is usually reserved for class names

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

Docstrings are usually a good idea.

Check out this question for more information on the proper use of globals. Based on what I know about your situation I don't think you need to use them.

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

If you don't know about `if name == 'main': you should read up on it.

if __name__ == "__main__":

Don't forget to use meaningful variable names and not override the builtins (i.e. file = "foo.txt" would override the file builtin)

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

You can learn more about context managers here

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

An edit using globals(), FOR WHICH NO USE CASE EXISTS AT ALL.

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()

edited May 23, 2017 at 12:28

CommunityBot

11 silver badge

answered Mar 21, 2013 at 17:06

John

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6 Comments

user2070615 Over a year ago

How do I make it so that whatever I type in: input("What will this data be saved as: ") becomes the variable?

John Over a year ago

It's generally considered bad to do this, so don't =). But globals()["my_shiny_variable"] = "a_shiny_variable" then print my_shiny_variable.

user2070615 Over a year ago

could you post the code how it would look. I think you mean: 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()["my_shiny_variable"] = "a_shiny_variable" my_shiny_variable = response.read()

user2070615 Over a year ago

You are very helpful by the way.

user2070615 Over a year ago

can anyone help me with this? I need for the variable that I enter in the the input prompt to trigger the HTML rather than the "x" variable.

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