How Can Python Dictionary Comprehensions Efficiently Create and Populate Dictionaries?

Dictionary Comprehensions in Python for Defining Keys

Dictionary comprehensions, like list comprehensions, offer a concise syntax for constructing dictionaries in Python. However, in contrast to list comprehensions, dictionary comprehensions create new dictionaries rather than modifying existing ones.

When using a dictionary comprehension, you must specify both the keys and values. The syntax is as follows:

{key: value for key, value in iterable}

For instance, to create a dictionary with keys ranging from 0 to 10 and all values set to True, you can use the following dictionary comprehension:

d = {n: True for n in range(11)}

This comprehension generates a new dictionary and assigns True to the keys from 0 to 10.

If you wish to set all keys to a different value, you can use the same syntax but specify a different value in place of True. For example, to assign the keys to their respective values, you can use:

d = {n: n for n in range(11)}

Unfortunately, there is no direct shortcut to simultaneously set multiple keys in an existing dictionary. You must either iterate over the keys and set them individually or create a new dictionary using a dictionary comprehension and merge it with the existing dictionary using the update() method.

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