3-1-3-17. Iterating Through Dictionaries with For Loops

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Iterating Through Dictionaries with For Loops

When you iterate through a dictionary using a for loop, doing it the normal way (for n in some_dict) will only give you access to the keys in the dictionary – which is what you’d want in some situations. In other cases, you’d want to iterate through both the keys and values in the dictionary. Let’s see how this is done in an example. Consider this dictionary that uses names of actors as keys and their characters as values.

cast = {
           "Jerry Seinfeld": "Jerry Seinfeld",
           "Julia Louis-Dreyfus": "Elaine Benes",
           "Jason Alexander": "George Costanza",
           "Michael Richards": "Cosmo Kramer"
       }

Iterating through it in the usual way with a for loop would give you just the keys, as shown below:

for key in cast:
    print(key)

This outputs:

Jerry Seinfeld
Julia Louis-Dreyfus
Jason Alexander
Michael Richards

If you wish to iterate through both keys and values, you can use the built-in method items like this:

for key, value in cast.items():
    print("Actor: {}    Role: {}".format(key, value))

This outputs:

Actor: Jerry Seinfeld    Role: Jerry Seinfeld
Actor: Julia Louis-Dreyfus    Role: Elaine Benes
Actor: Jason Alexander    Role: George Costanza
Actor: Michael Richards    Role: Cosmo Kramer

items is an awesome method that returns tuples of key, value pairs, which you can use to iterate over dictionaries in for loops.

Try It Out!

Test run and experiment with this example in the code editor below!

cast = {
           "Jerry Seinfeld": "Jerry Seinfeld",
           "Julia Louis-Dreyfus": "Elaine Benes",
           "Jason Alexander": "George Costanza",
           "Michael Richards": "Cosmo Kramer"
       }

print("Iterating through keys:")
for key in cast:
    print(key)

print("\nIterating through keys and values:")
for key, value in cast.items():
    print("Actor: {}    Role: {}".format(key, value))
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