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Find Length of a Python Dictionary

A dictionary is a data structure in Python used to store key-value pairs. The length of a dictionary is the number of key-value pairs present in the dictionary. In this tutorial, we will look at how to find the length of a dictionary in Python with the help of some examples.

How to get the length of a Python dictionary?

You can use the Python built-in len() function to find the length of a dictionary. It returns the number of key-value pairs present in the dictionary.

The following is the syntax –

# length of dictionary
len(my_dict)

Let’s look at some examples of using the above syntax.

Let’s create a dictionary containing the scores in Science of some students in a test and then use the len() function to find the length of the dictionary.

# create a dictionary
science_scores = {
    "Tim": 87,
    "Emma": 91,
    "Mark": 68
}
# get length of dictionary
print(len(science_scores))

Output:

3

We find that the length of the dictionary “science_scores” is 3. That is, it contains 3 key-value pairs, which in this example tells us the number of students-score pairs present in the dictionary.

Note that the length of a dictionary is the same as the length of the dictionary’s keys and values.

# length of dictionary
print(len(science_scores))
# length of dictionary keys
print(len(science_scores.keys()))
# length of dictionary values
print(len(science_scores.values()))

Output:

3
3
3

You can see that the length of the dictionary’s keys and values is the same as that of the dictionary.

Let’s look at another example.

# create a dictionary
science_scores = {}
# get length of dictionary
print(len(science_scores))

Output:

0

Here we see that the length for an empty dictionary is 0.

Length for a specific key in a dictionary

Let’s say instead of just the score in Science, you have the scores in three subjects – Science, Math, and English in a list for each student.

Now, if you just want to find the length of the value for a particular key, you can use the len() function as follows –

# create a dictionary
scores = {
    "Tim": [87, 74, 63],
    "Emma": [91, 82, 88],
    "Mark": [68, 91, 57]
}
# get length of a key's value
print(len(scores["Tim"]))

Output:

3

Here we first access the value for the key “Tim” and then find its length using the len() function. This gives us the number of scores present for “Tim”.

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Author

  • Piyush is a data scientist passionate about using data to understand things better and make informed decisions. In the past, he's worked as a Data Scientist for ZS and holds an engineering degree from IIT Roorkee. His hobbies include watching cricket, reading, and working on side projects.