enumerate() and dict.items()

Updated 8 Mar 2019.

enumerate is a handy built-in Python function that sometimes gets overlooked. It’s not life-changing, but it makes things a little cleaner and more concise.

Let’s say you want to loop through a list, but you want to access both the list items and the index value for each item. Here’s one way to do it:

>>> my_list = ['a', 'b', 'c']
>>> for index in range(0, len(my_list)):
...     item = my_list[index]
...     print(index, item)
...
0 a
1 b
2 c

However, you can do the same thing a little more gracefully with enumerate:

>>> for index, item in enumerate(my_list):
...     print(index, item)

items is similar to enumerate, but for dictionaries. If you were doing this…

>>> my_dict = {0:'a', 1:'b', 2:'c'}
>>> for key in my_dict.keys():
...     value = my_dict[key]
...     print(key, value)
...
0 a
1 b
2 c

…try this instead:

# Python 3
>>> for key, value in my_dict.items():
...     print(key, value)

items doesn’t exist in Python 2.7, but iteritems does the same thing:

# Python 2.7
>>> for key, value in my_dict.iteritems():
...     print(key, value)

Happy coding!