= NewbieMistakes =

Please feel free to share the things that tripped you up when you started with Django. We'll try to improve Django's error handling to catch such mistakes in the future.

== POST to views loses POST data ==

==== Symptom ====

You are having a form that does a POST to some view and the view doesn't get the POST data from the form.

==== Probable cause ====

You might missing the / at the end of the form action. If that is the case, the CommonMiddleware redirects
to the exact name of the view - and that allways includes a trailing /. Because it does so by using the
standard HTTP redirection through Location header, it can't pass on the POST data - and that's why it gets lost.

==== Solution ====

Allways make sure that your form actions end with / like this:

{{{
<form action="/registration/login/" method="POST">
<input name="username">
<input name="password" type="password">
</form>
}}}


== URLconf include() misbehaving ==

==== Symptom ====

You're trying to get your URLconf files to work, but getting cryptic errors about how there is no module 'index' (where 'index' is some function you are trying to assign as a view), or module 'foo' has no attribute 'urlpatterns'.

==== Probable cause ====

You may have tried to load your view files using include() in the URLconf file (in tutorial 3, this is myproject/settings/urls/main.py). The include() call assumes that the file it's loading is also a URLconf file.

==== Solution ====

Remove the include(). Just give the module and function name (e.g., {{{'myproject.apps.polls.views.polls.index'}}}) as a string, with no include() around it.


== Blank object names ==

==== Symptom ====

The automatic admin interface is showing nothing (or a single {{{&nbsp;}}}) in the "Select [object_type] to change" view.

==== Probable cause ====

You may have forgotten to create a {{{__str__()}}} function for your model. Django calls {{{__str__()}}} to find out how to display objects in the admin interface. An alternate cause is the string you return from {{{__str__()}}} includes brackets (an therefore looks like an html tag), and is cleaned up by the {{{strip_tags}}} template filter, resulting in blank entries.

==== Solution ====

Add a correct {{{__str__()}}} function (without brackets in the output) to all your models. Make it a habit so it becomes automatic.

== Integer & NULLS ==

==== Problem ====

When you have a Field: current_zip = meta.IntegerField(maxlength=5,blank=True)

django will create a not nullable field in the DB.  However leaving the field blank (in admin/web) django will try and insert a NULL value in the DB.

==== Solution ====

Add null=True:

current_zip = meta.IntegerField(maxlength=5,null=True,blank=True)


== Appending to a list in session doesn't work ==

==== Problem ====

If you have a list in your session, append operations don't get saved to the object.  

==== Solution ====

Copy the list out of the session object, append to it, then copy it back in:

{{{
sessionlist = request.session['my_list']
sessionlist.append(new_object)
request.session['my_list'] = sessionlist
}}}

== Errors about undefined attributes with one-char names ==

==== Problem ====

You get an !AttributeError with some weird attribute name that's only one char long. You don't have that attribute name anywhere in your code.

==== Solution ====

Search your model and code for situations where you have to pass a tuple of values and want to pass a tuple with one element - and that element is a string like in this sample:

{{{
#!python
class META:	
    ...
    admin = meta.Admin(
        list_display = ('total_price'),
        ...
    )
}}}

It's a standard python error - you are just missing a comma in the list_display assignement like this:

{{{
#!python
class META:	
    ...
    admin = meta.Admin(
        list_display = ('total_price',),
        ...
    )
}}}

Since a tuple is expected but a string provided, the code will merrily iterate over the characters of the string instead of the tuple elements - and that's where the single-char attribute names come from.