`in`

In Python, the in keyword is used for membership tests, for loops, comprehensions, and generator expressions. In all cases, its syntax involves a value and an iterable, value in iterable.

Python `in` Keyword Examples

Here’s a quick example to demonstrate how you can use the in keyword:

>>> # Membership tests
>>> fruits = ["apple", "banana", "cherry"]
>>> "banana" in fruits
True
>>> "orange" in fruits
False

>>> # Loop
>>> for fruit in fruits:
...     print(fruit)
...
apple
banana
cherry

>>> # Comprehenshion
>>> squares = [number**2 for number in [1, 2, 3]]
>>> squares
[1, 4, 9]

In this example, you use the in keyword to check whether "banana" is in the fruits list and get True. Similarly, you check for "orange," which isn’t in the list, and get False.

Next, you use in as part of a for loop that iterates over your list of fruits. Finally, you use in to create a list comprehension that builds a list of square values.

Python `in` Keyword Use Cases

Running membership tests to check for the existence of an element in an iterable
Implementing for loops to traverse Python iterables
Writing comprehensions for data transformation

Tutorial

Python's "in" and "not in" Operators: Check for Membership

In this tutorial, you'll learn how to check if a given value is present or absent in a collection of values using Python's in and not in operators, respectively. This type of check is known as membership test in Python.

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For additional information on related topics, take a look at the following resources: