Transforming Data with map()

map() applies a function to every element of a sequence, returning a new sequence with the results.

numbers = [1, 2, 3, 4, 5]
squared = map(lambda x: x ** 2, numbers)
print(list(squared))  # [1, 4, 9, 16, 25]

Think of it as: "transform each item according to this rule." You're not changing the original list, you're creating a new one.

The first argument is a function that takes one input and returns one output. The second is your sequence. map() returns an iterator, so you usually wrap it in list().

Compare to a loop:

# Loop approach
squared = []
for x in numbers:
    squared.append(x ** 2)

The map() version expresses the same idea more directly: "square each number."

Learn map and other transformations in my Functional Programming course.