Python dictionary length - How to count all the elements in a dictionary

The len() returns the number of items in a Python dictionary.

a = {'CA': 'California', 'NV': 'Nevada', 'TX': 'Texas'}
b = {'book': 5, 'pen': 9}

len_a = len(a)
len_b = len(b)

print(len_a)  # 3
print(len_b)  # 2

It is a Python built-in function counting all objects in an iterable. Even if you write the comma after the last element, the length of the dictionary remains.

stocks = {'Apple': 114, 'Google': 1532, 'Facebook': 265, }

print(len(stocks))  # 3

A comma after the last element is called "trailing comma".

Length of a dictionary with a trailing comma and an empty dictionary

In Python, a dictionary can have a trailing comma and it's ignored to count elements. The length of an empty dictionary is 0.

d = {'book': 24, }
e = {}

print(len(d))  # 1

print(type(e))  # <class 'dict'>
print(len(e))  # 0