for — Intermediate Examples

Starts a loop that iterates over a sequence or iterable

EasyIntermediateAdvancedExpert

List comprehensions

Concise syntax for building lists from loops.

python
# Basic comprehension
squares = [x**2 for x in range(10)]
print(squares)

# With filter
evens = [x for x in range(20) if x % 2 == 0]
print(evens)

# Nested comprehension (matrix)
matrix = [[i * j for j in range(1, 4)] for i in range(1, 4)]
for row in matrix:
    print(row)

# Dict comprehension
word = "mississippi"
freq = {ch: word.count(ch) for ch in set(word)}
print(freq)

Comprehensions are syntactic sugar for common for-loop-and-append patterns. They are often faster because the append is optimized internally.

Iterating over dictionaries

Different ways to loop over dict keys, values, and items.

python
scores = {"Alice": 95, "Bob": 87, "Charlie": 92}

# Keys (default)
for name in scores:
    print(name)

# Values
for score in scores.values():
    print(score)

# Items (key-value pairs)
for name, score in scores.items():
    print(f"{name}: {score}")

# Sorted iteration
for name in sorted(scores, key=scores.get, reverse=True):
    print(f"{name}: {scores[name]}")

Iterating over a dict yields keys by default. Use .values() for values, .items() for key-value pairs, and sorted() for ordered iteration.

Want to try these examples interactively?

Open Intermediate Playground
← Easy ExamplesAdvanced Examples →