Question

I’m trying to perform an operation on all the elements from a single field of a model, but I’m getting an error:

list indices must be integers, not tuple

Here’s my index function in views.py:

design_list = Design.objects.values_list().order_by('-date_submitted')[:10]

x=list(design_list)
for i in x:
    b = list(x[i]) # ERROR RELATES TO THIS LINE
    c = b[2]
    b[2] = datetimeConvertToHumanReadable(c) 
    new_list[i] = b

return render_to_response('index.html', {
    'design_list': new_list,    
})

I’m sure this is a common problem, does anyone know what I’m doing wrong?

Answer 1

Python is not C – the for x in y loop does not loop over indices, but over the items themselves.

design_list is a list of tuples, so you can treat it as such. Tuples are immutable, therefore you’ll need to create a new list. A list comprehension would probably be best.

# Create a new list of tuples
new_list = [row[:2] + (datetimeConvertToHumanReadable(row[2]),) + row[3:]
            for row in x]

However, it doesn’t seem like you really need to use tuples, since you were confused by the error. If this is the case, then don’t use values_list (which returns tuples), but just use order_by, and reference the field directly (I’ll assume it’s called date_submitted).

design_list = Design.objects.order_by('-date_submitted')[:10]

x=list(design_list)
for row in x:
    row.date_submitted = datetimeConvertToHumanReadable(row.date_submitted) 

return render_to_response('index.html', {
    'design_list': x,
})