How to Check if a Key Exists in a Python Dictionary

Dictionaries in Python are very useful because they allow you to add, read, and remove key-value pairs.

When working with them, you will oftentimes need to know if a dictionary contains a key or not.

In this post, we'll learn how to check if a key exists in a dictionary in Python.

How to check if a key exists in a dictionary in Python

To start, let's create a dictionary:

PYTHON
dictionary = {
    "name": "John",
    "age": 30,
    "city": "New York"
}

print(dictionary)

The output will be:

PYTHON
{'name': 'John', 'age': 30, 'city': 'New York'}

Now, let's say we want to check if the key "name" exists in the dictionary.

The best way to do this is to simply use the in keyword.

This keyword will return True if the key exists in the dictionary, and False if it doesn't.

PYTHON
dictionary = {
    "name": "John",
    "age": 30,
    "city": "New York"
}

key = "name"

if key in dictionary:
    print("Key exists in dictionary")
else:
    print("Key does not exist in dictionary")

BASH
Key exists in dictionary

Alternatively, you can also set the output of the in keyword to a variable:

PYTHON
dictionary = {
    "name": "John",
    "age": 30,
    "city": "New York"
}

key = "name"

key_exists = key in dictionary

print(key_exists)

BASH
True

Conclusion

In this post, we learned how to check if a key exists in a dictionary in Python.

Simply use the in keyword on a dictionary and pass it the key you want to check.

Thanks for reading!

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