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Editorial Team
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Asked: 2026-06-17T09:29:34+00:00

When I run the following function: def checkChange(): for user in userLinks: url =

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When I run the following function:

def checkChange():
    for user in userLinks:
        url = userLinks[user]
        response = urllib2.urlopen(url)  
        html = response.read()

I get 

Traceback (most recent call last):
  File "InStockBot.py", line 34, in <module>
    checkChange()
  File "InStockBot.py", line 24, in checkChange
    html = response.read()
UnboundLocalError: local variable 'response' referenced before assignment

Which makes no sense to me. I have no global var response. I expect it to work as below, normally.

>>> url="http://google.com"
>>> response = urllib2.urlopen(url)  
>>> html = response.read()
>>> html
'<!doctype html>

Anyone know why I get this error?

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1 Answer

  1. Editorial Team

    You’re mixing tabs and spaces. Looking at the raw code you pasted:

    '    def checkChange():'
'    \tfor user in userLinks:'
'    \t\turl = userLinks[user]'
'    \t\tresponse = urllib2.urlopen(url)  '
'            html = response.read()'

    You can see the switch in the last line. Effectively, this means that the html = response.read() line isn’t indented as far as you think it is, meaning that if userLinks is empty, you’ll get:

    Traceback (most recent call last):
  File "inde.py", line 10, in <module>
    checkChange()
  File "inde.py", line 5, in checkChange
    html = response.read()
UnboundLocalError: local variable 'response' referenced before assignment

    Run your code using python -tt yourprogramname.py to confirm this, and switch to always using four-space tabs.

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