According to the Python documentation, the enumerate function is a built in function that returns an enumerate object. Another popular article on the subject describes it as a function that allows you to “generate iterator element along with index”. I find these two definitions unclear. Here’s an explanation that makes more sense: the enumerate function allows you to iterate through a list or sequence whilst keeping track of the indexes of the elements. In other words, enumerate adds a counter to an iterable.
Syntax
The syntax of enumerate() is:
enumerate(sequence, start=0)
The sequence parameter must be a sequence such as a string, a tuple or a list, an iterator or some other object which supports iteration.
The start parameter allows us to tell enumerate() where to start the index or counter.
Example: How enumerate works in Python
names = ['Bob', 'Alice', 'Spencer', 'Mark', 'Jane'] >>> for index, name in enumerate(names): ... print index, name 0 Bob 1 Alice 2 Spencer 3 Mark 4 Jane >>> for index, name in enumerate(names, start=1): ... print index, name 1 Bob 2 Alice 3 Spencer 4 Mark 5 Jane
Using enumerate to print the index of an element is similar to doing this:
>>> for i in range(len(names)):
... name = names[i]
... print i + 1, name,
1 Bob
2 Alice
3 Spencer
4 Mark
5 Jane
I prefer using enumerate because it’s a built in and it looks more pythonic. I have found the enumerate() function incredibly useful when working with nested for loops and also when going through data arranged in a grid-like format like Spreadsheets. This Quora thread discusses some of the reasons why you would want to use enumerate.
That is all for this week. Thanks for reading.