Is there a pythonic way of knowing when the first and last loop in a for is being passed through?

Question

I have a template in which I placed, let's say 5 forms, but all disabled to be posted except for the first one. The next form can only be filled if I click a button that enables it first.

I'm looking for a way to implement a Django-like forloop.last templatetag variable in a for loop inside an acceptance test to decide whether to execute a method that enables the next form or not.

Basically what I need to do is something like:

for form_data in step.hashes:
    # get and fill the current form with data in form_data
    if not forloop.last:
        # click the button that enables the next form
# submit all filled forms

Answer 1

I don't know of anything built-in, but you can easily write a generator to give you the required information:

def firstlast(seq):
    seq = iter(seq)
    el = prev = next(seq)
    is_first = True
    for el in seq:
        yield prev, is_first, False
        is_first = False
        prev = el
    yield el, is_first, True


>>> list(firstlast(range(4)))
[(0, True, False), (1, False, False), (2, False, False), (3, False, True)]
>>> list(firstlast(range(0)))
[]
>>> list(firstlast(range(1)))
[(0, True, True)]
>>> list(firstlast(range(2)))
[(0, True, False), (1, False, True)]
>>> for count, is_first, is_last in firstlast(range(3)):
    print(count, "first!" if is_first else "", "last!" if is_last else "")


0 first! 
1  
2  last!

Answer 2

You could use enumerate and compare the counter with the length of the list:

for i, form_data in enumerate(step.hashes):
    if i < len(step.hashes):
        whatever()