In List Comprehension, an expression is a piece of code that is applied to each element of the iterable to create a new list. The expression can be a single value, a variable, an operation, a function call, or any other Python code that returns a value.
In the syntax of List Comprehension:
new_list = [expression for item in iterable if condition]
The expression is the part of the code that creates a new element to be added to the new list. It is applied to each element of the iterable that satisfies the condition, which is an optional part of List Comprehension.
For example, let's say we have a list of numbers [1, 2, 3, 4, 5], and we want to create a new list that contains the squares of each number in the original list. We can use List Comprehension to achieve this as follows:
numbers = [1, 2, 3, 4, 5]
squares = [x**2 for x in numbers]
print(squares) # Output: [1, 4, 9, 16, 25]
In this example, the expression is x**2, which is applied to each element x of the iterable numbers. The resulting squares are added to the new list squares.
Thus, an expression in List Comprehension is a piece of code that is applied to each element of the iterable to create a new list. The expression can be any valid Python code that returns a value.
