“For” loop first iteration

Question

I would like to inquire if there is an elegant pythonic way of executing some function on the first loop iteration. The only possibility I can think of is:

f         


        

Answer 1

I think the first S.Lott solution is the best, but there's another choice if you're using a pretty recent python (>= 2.6 I think, since izip_longest doesn't seem available before that version) that lets doing different things for the first element and successive one, and can be easily modified to do distinct operations for 1st, 2nd, 3rd element... as well.

from itertools import izip_longest

seq = [1, 2, 3, 4, 5]

def headfunc(value):
    # do something
    print "1st value: %s" % value

def tailfunc(value):
    # do something else
    print "this is another value: %s" % value

def foo(value):
    print "perform this at ANY iteration."

for member, func in izip_longest(seq, [headfunc], fillvalue=tailfunc):
    func(member)
    foo(member)