Get a value from a dictionary by key in Python

This article explains how to get a value from a dictionary (dict) by key in Python.

If you want to extract keys based on their values, see the following article.

• Get keys from a dictionary by value in Python

You can get all the values in a dictionary as a list using the list() function with the values() method.

• Iterate through dictionary keys and values in Python

d = {'key1': 1, 'key2': 2, 'key3': 3}

print(list(d.values()))
# [1, 2, 3]

Get a value from a dictionary with dict[key] (KeyError for non-existent keys)

In Python, you can get a value from a dictionary by specifying the key like dict[key].

d = {'key1': 'val1', 'key2': 'val2', 'key3': 'val3'}

print(d['key1'])
# val1

In this case, KeyError is raised if the key does not exist.

# print(d['key4'])
# KeyError: 'key4'

Specifying a non-existent key is not a problem if you want to add a new element to the dictionary.

d['key4'] = 'val4'
print(d)
# {'key1': 'val1', 'key2': 'val2', 'key3': 'val3', 'key4': 'val4'}

For more information about adding items to the dictionary, see the following article.

• Add, merge, update dictionaries in Python

Use in to check if the key exists in the dictionary.

• Check if a key/value exists in a dictionary in Python

Use dict.get() to get the default value for non-existent keys

You can use the get() method of a dictionary (dict) to get a value without an error. If the key does not exist, a default value can be returned.

• Built-in Types - dict.get() — Python 3.11.3 documentation

Specify the key as the first argument. If the key exists, the corresponding value is returned. Otherwise, None is returned.

d = {'key1': 'val1', 'key2': 'val2', 'key3': 'val3'}

print(d.get('key1'))
# val1

print(d.get('key4'))
# None

You can specify the default value in the second argument, to be returned when the key does not exist.

print(d.get('key4', 'NO KEY'))
# NO KEY

print(d.get('key4', 100))
# 100

The original dictionary remains unchanged.

print(d)
# {'key1': 'val1', 'key2': 'val2', 'key3': 'val3'}