"Too many values to unpack" Exception


Question

I'm working on a project in Django and I've just started trying to extend the User model in order to make user profiles.

Unfortunately, I've run into a problem: Every time I try to get the user's profile inside of a template (user.get_template.lastIP, for example), I get the following error:

Environment:

Request Method: GET
Request URL: http://localhost:8000/
Django Version: 1.1
Python Version: 2.6.1

Template error:
In template /path/to/base.tpl, error at line 19
   Caught an exception while rendering: too many values to unpack

19 :                Hello, {{user.username}} ({{ user.get_profile.rep}}). How's it goin? Logout


Exception Type: TemplateSyntaxError at /
Exception Value: Caught an exception while rendering: too many values to unpack

Any ideas as to what's going on or what I'm doing wrong?

1
105
9/25/2009 10:56:01 PM

Accepted Answer

That exception means that you are trying to unpack a tuple, but the tuple has too many values with respect to the number of target variables. For example: this work, and prints 1, then 2, then 3

def returnATupleWithThreeValues():
    return (1,2,3)
a,b,c = returnATupleWithThreeValues()
print a
print b
print c

But this raises your error

def returnATupleWithThreeValues():
    return (1,2,3)
a,b = returnATupleWithThreeValues()
print a
print b

raises

Traceback (most recent call last):
  File "c.py", line 3, in ?
    a,b = returnATupleWithThreeValues()
ValueError: too many values to unpack

Now, the reason why this happens in your case, I don't know, but maybe this answer will point you in the right direction.

171
9/25/2009 10:13:22 PM

try unpacking in one variable,

python will handle it as a list,

then unpack from the list

def returnATupleWithThreeValues():
    return (1,2,3)
a = returnATupleWithThreeValues() # a is a list (1,2,3)
print a[0] # list[0] = 1
print a[1] # list[1] = 2
print a[2] # list[2] = 3

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