Python Dictionary Comprehension

In Python, dictionary comprehensions offer a concise way to generate new dictionaries. While they are similar to list comprehensions, there are some notable differences.

Key-Only Dictionary Comprehension

Unlike the question suggests, you cannot create a dictionary comprehension for the keys. You must explicitly specify the keys and values. For example:

d = {n: n**2 for n in range(5)}

This creates a dictionary with keys from 0 to 4 and values equal to the square of the corresponding key.

Setting a Single Value for Multiple Keys

To set the same value for multiple keys, you can use the following syntax:

d = {n: True for n in range(5)}

This creates a dictionary with keys from 0 to 4, all with the value True.

Setting Multiple Values for Multiple Keys

As the question points out, it is not possible to specify multiple values for the same key using a dictionary comprehension. To achieve this, you can either manually assign values using a loop or create a separate dictionary and update the existing one using update():

# Create a new dictionary
new_dict = {n: n for n in range(5)}

# Update the existing dictionary
existing_dict.update(new_dict)