dict.items() function

Question

gender_freq = {}

for row in moma:
    gender = row[5]
    if gender not in gender_freq:
        gender_freq[gender] = 1
    else:
        gender_freq[gender] += 1

for gender, num in gender_freq.items():
    template = "There are {n:,} artworks by {g} artists"
    print(template.format(g=gender, n=num))

Why need .items() in for loop? I don't know what is .items() function and I can't understand why need it.

gender_freq is a dict, `items` gives you both keys and values, without `items` it will give only keys. — Raymond Reddington, Mar 03 '21 at 08:35
Does this answer your question? [How do I print the key-value pairs of a dictionary in python](https://stackoverflow.com/questions/26660654/how-do-i-print-the-key-value-pairs-of-a-dictionary-in-python) — Gino Mempin, Mar 03 '21 at 09:40
I recommend using the Python docs as reference. The [Dictionaries](https://docs.python.org/3/tutorial/datastructures.html#dictionaries) section explains `.items` as part of [Looping Techniques](https://docs.python.org/3/tutorial/datastructures.html#looping-techniques). — Gino Mempin, Mar 03 '21 at 09:49

score 2 · Accepted Answer · answered Mar 03 '21 at 08:40

2

.items() returns a list with tuples corresponding to (key, value) pair in the dictionary.

this is your little example:

example = {
    'female': 8, 
    'male': 4
}

example.items() is

[('female', 8), ('male', 4)]

and when you do:

for gender, num in example.items():

gender will take these values: female, male

and num will take these values: 8, 4

when using items() you are iterating through the items of the dictionary in parallel.

answered Mar 03 '21 at 08:40

alexzander

1,586
1
9
21

my pleasure to help. – alexzander Mar 03 '21 at 08:55
It's *not* a list, unless you're still using Python 2.x: https://docs.python.org/3/whatsnew/3.0.html#views-and-iterators-instead-of-lists – jonrsharpe Mar 17 '21 at 07:48

score 1 · Answer 2 · answered Mar 03 '21 at 08:42

items() allows you to fetch the key/value pair of the dict in your for loop, this will avoid you looping on keys and asking for the value each time like so:

for gender in gender_freq:
    print(template.format(g=gender, n=gender_freq[gender]))

One more thing though, use the defaultdict this will allow you to avoid the check for the key each time you want to populate your dict:

from collections import defaultdict

gender_freq = defaultdict(int)

for row in moma:
    gender = row[5]
    gender_freq[gender] += 1

dict.items() function

2 Answers2