Python for loop over a dictionary

April 29, 2021

Jeeze, just had to remind myself of this. I got the blog up and going again to be able to note stuff like this down so here we go.

For loops on a dictionary in Python. There’s an option of looping over it raw, or include the use of its methods: keys(), values(), items().

When looping over it raw, you just get the keys back (makes me wonder why keys() exists in the first place, but that’s a lesson for another day):

>>> myDictionary = {'a':'123','b':'456','c':'789'}
>>> 
>>> for item in myDictionary:
...     print(item)
... 
a
b
c

You can see we get the same thing if we use .keys():

>>> for item in myDictionary.keys():
...     print(item)
... 
a
b
c

We can iterate over only its values:

>>> for item in myDictionary.values():
...     print(item)
... 
123
456
789

Lastly we can use items() to get the full dataset:

>>> for item in myDictionary.items():
...     print(item)
... 
('a', '123')
('b', '456')
('c', '789')

The bonus with this though is that because this is a dictionary in which there are multiple items being presented, you can perform a multiple assignment like a, b = 0, 1 where a becomes 0 and b becomes 1:

>>> for key, value in myDictionary.items():
...     print(f'key: {key}, value: {value}')
... 
key: a, value: 123
key: b, value: 456
key: c, value: 789

python