range() / enumerate() / zip()

range(stop)
range(start, stop)
range(start, stop, step)

# Returns each element of an iterable paired with its index.
enumerate(iterable, start=0)

# Combines multiple iterables element by element.
zip(iterable1, iterable2, ...)

# Returns an iterable in reverse order.
reversed(sequence)

range_basic.py

for i in range(5):
    print(i, end=" ")
print()

for i in range(2, 10, 2):
    print(i, end=" ")
print()

for i in range(5, 0, -1):
    print(i, end=" ")
print()

nums = list(range(1, 6))
print(nums)

Running the code produces the following output:

python3 range_basic.py
0 1 2 3 4
2 4 6 8
5 4 3 2 1
[1, 2, 3, 4, 5]

enumerate_example.py

pilots = ["Ikari Shinji", "Ayanami Rei", "Soryu Asuka"]

for i, pilot in enumerate(pilots):
    print(f"{i}: {pilot}")

print()

for i, pilot in enumerate(pilots, start=1):
    print(f"#{i}: {pilot}")

Running the code produces the following output:

python3 enumerate_example.py
0: Ikari Shinji
1: Ayanami Rei
2: Soryu Asuka

#1: Ikari Shinji
#2: Ayanami Rei
#3: Soryu Asuka

zip_reversed_example.py

names = ["Ayanami Rei", "Ikari Shinji", "Soryu Asuka"]
scores = [85, 92, 78]
for name, score in zip(names, scores):
    print(f"{name}: {score} points")

print()

person = dict(zip(["name", "age", "org"], ["Ayanami Rei", 14, "NERV"]))
print(person)

print()

for item in reversed(names):
    print(item, end=" ")
print()

Running the code produces the following output:

python3 zip_reversed_example.py
Ayanami Rei: 85 points
Ikari Shinji: 92 points
Soryu Asuka: 78 points

{'name': 'Ayanami Rei', 'age': 14, 'org': 'NERV'}

Soryu Asuka Ikari Shinji Ayanami Rei

Common Mistake 1: Expecting range() to include the stop value

range(5) generates values from 0 to 4. The value 5 is not included. To loop from 1 through 5, write range(1, 6).

for i in range(5):
    print(i)

The same logic can also be written as:

for i in range(1, 6):
    print(i)

Common Mistake 2: Expecting zip() to process all elements from lists of different lengths

zip() stops when the shortest iterable is exhausted. To process all elements from iterables of different lengths, you can use itertools.zip_longest().

names = ["Ikari Shinji", "Ayanami Rei", "Soryu Asuka"]
scores = [85, 92]
for name, score in zip(names, scores):
    print(f"{name}: {score} points")

The same logic can also be written as:

from itertools import zip_longest

names = ["Ikari Shinji", "Ayanami Rei", "Soryu Asuka"]
scores = [85, 92]
for name, score in zip_longest(names, scores, fillvalue=0):
    print(f"{name}: {score} points")

range() returns a lazy-evaluated object that is highly memory-efficient. Even range(1000000) does not load a million integers into memory at once — it generates values on demand. The stop value is not included in the result (e.g., range(5) yields 0 through 4; 5 is not included).

enumerate() eliminates the need to manage indexes manually. Writing for i, fruit in enumerate(fruits): is considered more Pythonic than for i in range(len(fruits)):.

zip() stops when the shortest iterable is exhausted. If you need to process all elements from iterables of different lengths, you can use itertools.zip_longest(). zip() is also commonly used to loop over multiple lists together, and is often paired with sorted() for sorting operations.