Python zip() & enumerate()

The zip() Function

zip(list1, list2, ...) pairs up corresponding elements from multiple iterables into tuples, stopping as soon as the shortest input runs out.

It's the standard way to loop over two related lists in lockstep, like names and their corresponding scores, without manually indexing into both.

Example: The zip() Function

names = ["Alex", "Sam"]
scores = [90, 80]
for name, score in zip(names, scores):  # pairs elements from both lists together
    print(name, score)

Unzipping Lists

Prefixing a zipped result with * inside another zip() call unzips it back into separate lists, splitting paired tuples apart -- effectively zip() undoing its own operation, a genuinely useful but often-overlooked trick.

Example: Unzipping Lists

pairs = [(1, "a"), (2, "b")]
numbers, letters = zip(*pairs)  # * unzips the pairs back into separate tuples
print(numbers, letters)

The enumerate() Function

enumerate(iterable) wraps a sequence so that looping over it yields (index, value) pairs automatically, replacing the error-prone manual pattern of maintaining a separate counter variable that you increment by hand inside the loop.

Example: The enumerate() Function

fruits = ["apple", "banana"]
for index, fruit in enumerate(fruits):  # yields (index, value) pairs automatically
    print(index, fruit)

Custom Starting Index

Passing a start value to enumerate(iterable, start=1) begins the index count from that number instead of the default 0, useful whenever you want 1-based numbering to match how the output will actually be displayed to a person.

Example: Custom Starting Index

fruits = ["apple", "banana"]
for index, fruit in enumerate(fruits, start=1):  # index counting begins at 1 instead of 0
    print(index, fruit)

Combining zip() and enumerate()

Nesting zip() inside enumerate(), as in enumerate(zip(list1, list2)), lets you loop through multiple paired lists while also tracking a running index for each pair -- combining both patterns when you need both the position and the paired values together.

Example: Combining zip() and enumerate()

names = ["Alex", "Sam"]
scores = [90, 80]
for i, (name, score) in enumerate(zip(names, scores)):  # index plus paired values together
    print(i, name, score)