5. Dictionary Comprehension

Quiz: 0/5

A dictionary comprehension is a shorter, easier way to create a dictionary from an iterable (like a list or a tuple). It allows you to quickly create a dictionary with key-value pairs.

The basic syntax looks like this:

{key: value for key, value in iterable}

• key: value represents the key-value pair you want in your dictionary.
• iterable is the thing you're looping through (like a list or a tuple).

Example: Creating a dictionary from a list of tuples

Let's say you have a list of tuples like this:

pairs = [("apple", 3), ("banana", 5), ("cherry", 2)]

You can use dictionary comprehension to convert this list into a dictionary:

fruit_dict = {fruit: count for fruit, count in pairs}
print(fruit_dict)

Output:

{'apple': 3, 'banana': 5, 'cherry': 2}

Here, the fruit becomes the key, and the count becomes the value for each item in the list.

Set comprehension

A set comprehension works similarly to dictionary comprehension, but it creates a set instead of a dictionary. A set is just a collection of unique items, without key-value pairs.

The syntax for a set comprehension looks like this:

{expression for item in iterable}

• expression is what you want to put in the set.
• iterable is the thing you're looping through.

Example: Creating a set from a list

Let's say you have a list of numbers and you want to create a set of squared values:

numbers = [1, 2, 3, 4, 2, 3]
squares = {num ** 2 for num in numbers}
print(squares)

Output:

{1, 4, 9, 16}

Notice that the set only includes unique values, so even though 2 and 3 appeared twice in the original list, their squared values only appear once in the set.

Summary:

• Dictionary comprehension creates a dictionary with key-value pairs from an iterable.
• Set comprehension creates a set (a collection of unique values) from an iterable.

Both are useful for writing cleaner, more efficient code!