enumerate()

In this lecture we will learn about an extremely useful built-in function: enumerate(). Enumerate allows you to keep a count as you iterate through an object. It does this by returning a tuple in the form (count,element). The function itself is equivalent to:

def enumerate(sequence, start=0):
    n = start
    for elem in sequence:
        yield n, elem
        n += 1

Example

In [1]:
lst = ['a','b','c']

for number,item in enumerate(lst):
    print number
    print item
0
a
1
b
2
c

enumerate() becomes particularly useful when you have a case where you need to have some sort of tracker. For example:

In [3]:
for count,item in enumerate(lst):
    if count >= 2:
        break
    else:
        print item
a
b

Great! You should now have a good understanding of enumerate and its potential use cases.