What it does

zip() combines multiple sequences (lists, tuples, etc.) into pairs (or tuples) of corresponding elements. It stops when the shortest sequence ends.

Basic usage

names = ['Alice', 'Bob', 'Charlie']
ages = [25, 30, 35]

# Loop over both lists together:
for name, age in zip(names, ages):
    print(f"{name} is {age} years old")

# Output:
# Alice is 25 years old
# Bob is 30 years old
# Charlie is 35 years old

Creating pairs

names = ['Alice', 'Bob']
ages = [25, 30]

# Convert to list of tuples:
pairs = list(zip(names, ages))
print(pairs)  # [('Alice', 25), ('Bob', 30)]

Different lengths

zip stops at the shortest sequence:

list1 = [1, 2, 3, 4]
list2 = ['a', 'b']

for x, y in zip(list1, list2):
    print(x, y)

# Output:
# 1 a
# 2 b
# (stops here, ignores 3 and 4)

Unzipping

Use * to "unzip" back into separate lists:

pairs = [('Alice', 25), ('Bob', 30)]
names, ages = zip(*pairs)
print(names)  # ('Alice', 'Bob')
print(ages)   # (25, 30)

When to use zip

  • Looping over multiple lists simultaneously
  • Creating dictionaries from two lists
  • Processing related data in parallel
  • Transposing data (rows to columns)