On Mon, May 18, 2009 at 6:53 PM, Mohan Parthasarathy <[email protected]>wrote:
> Hi,
>
> class CategoryAdmin(admin.ModelAdmin):
> prepopulated_fields = {'slug' : ('title', )}
>
> Why does the format require a comma after "title'. It is still a valid
> tuple without a comma, right ?
No, it's a string. Single-element tuples require a trailing comma (more
than they require the parens, actually). See:
http://docs.python.org/tutorial/datastructures.html#tuples-and-sequences
> Without that, I keep getting errors.
>
You're actually lucky there. Often these sneak by without an immediate
error, and at some point way later some code iterates over your "tuple",
producing, since strings are iterable too, the unexpected sequence 't', 'i',
't', 'l', 'e'. That sort of thing often leads to much harder to find
bugs....or maybe that's the error you encountered?
>
> Sorry, If this was a dumb question. I am parallely doing python and django.
> Atleast creating a dictionary in python did not require a comma for the
> tuple
>
Not dumb...it's a Python gotcha that routinely trips up newcomers to the
language. I'd recheck that your dictionary-creation code is actually
creating what you want. It may look like it's working but lead to problems
down the line if you are missing trailing commas on what are supposed to be
single-element tuples.
Karen
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