Python · Theory

List Comprehension in Python

Theory

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List Comprehension in Python

List comprehension builds a new list in one expression. Shape: [n * n for n in nums if n % 2 == 1]. Same result as a for-loop plus append, shorter when the idea is simple. squares = [x * x for x in range(5)] → [0, 1, 4, 9, 16]. Optional if filters items.

Don’t nest three comprehensions. If you cannot say it in one breath, use a loop. Write the comprehension and the equivalent for-loop in the viva — same output, two styles.

List Comprehension in Python — output — [1, 9, 25]. Odds 1,3,5 squared.

Diagram

nums = [1, 2, 3, 4, 5]
         │ n*n if odd
         ▼
      [1, 9, 25]

Exam tip

Comprehension vs loop — same result.

Example

# List comprehension
nums = [1, 2, 3, 4, 5]
print([n * n for n in nums if n % 2 == 1])

List Comprehension in Python — output: [1, 9, 25]. Odds 1,3,5 squared.

Short notes

Def[expr for x in seq if cond].
RuleBuilds a new list.
TrapOver-nested comprehensions.

Python · Theory

List Comprehension in Python

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Theory

47/268

List Comprehension in Python

Don’t nest three comprehensions. If you cannot say it in one breath, use a loop. Write the comprehension and the equivalent for-loop in the viva — same output, two styles.

List Comprehension in Python — output — [1, 9, 25]. Odds 1,3,5 squared.

Diagram

nums = [1, 2, 3, 4, 5]
         │ n*n if odd
         ▼
      [1, 9, 25]

Exam tip

Comprehension vs loop — same result.

Example

# List comprehension
nums = [1, 2, 3, 4, 5]
print([n * n for n in nums if n % 2 == 1])

List Comprehension in Python — output: [1, 9, 25]. Odds 1,3,5 squared.

Short notes

Def[expr for x in seq if cond].
RuleBuilds a new list.
TrapOver-nested comprehensions.

List Comprehension in Python

Example

Short notes

Questions

List Comprehension in Python

Example

Short notes

Questions