Python view dictionary Keys and Values

In python, we can view a dictionary’s keys and values using the dictionary functions keys() and values() respectively. In this tutorial, we’ll look at how to use these functions along with some examples.

Before we proceed, here’s a quick refresher on dictionaries in python – Dictionaries are a collection of items used for storing key to value mappings. They are mutable and hence we can update the dictionary by adding new key-value pairs, removing existing key-value pairs, or changing the value corresponding to a key. For more, check out our guide on dictionaries and other data structures in python.

View Keys and Values of a python dictionary

The dictionary functions keys() and values() can be used to view a dictionary’s keys and values. They return a view object that provides a dynamic view of the dictionary’s entries, meaning when the dictionary changes, the view reflects these changes.

The keys() function

The python dictionary keys() function gives a view object that displays a list of all the keys in the dictionary. The following is the syntax:

sample_dict.keys()

Here, sample_dict is the dictionary whose keys you want to get.

Parameters: The keys() function does not take any parameters.

Returns: It returns a view object of the dictionary’s keys. For more on dictionary view objects, refer to the python docs.

Example 1: Using the keys() function to display a dictionary’s keys

# dictionary of a sample portfolio
shares1 = {'APPL': 100, 'GOOG': 50}
shares2 = {}

# print the keys of the shares1 and shares2
print("Keys of shares1:", shares1.keys())
print("Keys of shares2:", shares2.keys())

Output:

Keys of shares1: dict_keys(['APPL', 'GOOG'])
Keys of shares2: dict_keys([])

In the above example, the keys() function is used to get the keys of dictionaries shares1 and shares2. We print out the returned objects for both the dictionaries. We see that for the dict shares1, a view object with its keys in a list is returned while for the empty dict shares2, a view object with an empty list is returned.

Example 2: When a dictionary is updated

# dictionary of a sample portfolio
shares = {'APPL': 100, 'GOOG': 50}
keys = shares.keys()
# print the keys of the shares
print("Keys of shares:", keys)

# update the dictionary
shares.update({'TSLA': 80})
# print the keys of the shares
print("Keys of shares:", keys)

Output:

Keys of shares: dict_keys(['APPL', 'GOOG'])
Keys of shares: dict_keys(['APPL', 'GOOG', 'TSLA'])

In the above example, we update the dictionary shares and print its keys before and after the update. We see that keys gets automatically updated when a change is made to the dictionary.

The values() function

The python dictionary values() function gives a view object of the dictionary’s values. It has a similar syntax as that of the keys function:

sample_dict.values()

Here, sample_dict is the dictionary whose values you want to get.

Parameters: The values() function does not take any parameters.

Returns: It returns a view object of the dictionary’s values.

Example 1: Display a dictionary’s values using values()

# dictionary of a sample portfolio
shares1 = {'APPL': 100, 'GOOG': 50}
shares2 = {}

# print the values of the shares1 and shares2
print("Values of shares1:", shares1.values())
print("Values of shares2:", shares2.values())

Output:

Values of shares1: dict_values([100, 50])
Values of shares2: dict_values([])

In the above example, the values() function is used to get the values of shares1 and shares2 dictionaries. We see that for the empty dictionary we get view object with an empty list.

Example 2: When the dictionary is updated

# dictionary of a sample portfolio
shares = {'APPL': 100, 'GOOG': 50}
values = shares.values()
# print the values of the shares
print("Values of shares:", values)

# update the dictionary
shares.update({'TSLA': 80})
# print the values of the shares
print("Values of shares:", values)

Output:

Values of shares: dict_values([100, 50])
Values of shares: dict_values([100, 50, 80])

In the above example, we print the values of the dictionary shares before and after the update. We see that values gets automatically updated when a change is made to the dictionary.

Dictionary view objects behavior:

The dictionary view object can be iterated over and supports membership tests.

Example 1: Iterate over a dictionary keys

# dictionary of a sample portfolio
shares = {'APPL': 100, 'GOOG': 50}
# dictionary keys view object
keys = shares.keys()

# iterate over keys
for k in keys:
    print(k)

Output:

APPL
GOOG

In the above example, we iterate over keys which is a dictionary view object returned by the keys() function.

Example 2: Membership test

# dictionary of a sample portfolio
shares = {'APPL': 100, 'GOOG': 50}
# dictionary keys view object
keys = shares.keys()

# Membership test using in
print('APPL' in keys)

Output:

True

In the above example, we test for the membership of a key in the view object returned by the keys() function using the membership operator in.