List manipulation

Produces a repeated sequence of list elements without explicit loops.

Testing: generate repeated test data; Data processing: create padding rows in a matrix

Common in Python scripts, data processing, testing, and algorithmic code where list repetition is needed.

list * n

... * ...

sequence: list, count: int

• list comprehension
• for loops
• itertools.repeat
• * operator for strings

• Using list multiplication vs. using [item] * n for a single element
• or using list.extend in a loop.

Confusing list multiplication with deep copying; modifies nested lists unexpectedly because it creates shallow copies.

String repetition (s * n) creates a new string; unlike lists, strings are immutable so no shared references.

Coming from languages like Java or C++ where you might expect loops; Python's * operator for lists is concise but can be misleading for nested structures.

• list comprehension
• itertools.repeat
• seq * n (string repetition)

Only works for immutable elements or when shallow copies are acceptable; for deep copies use copy.deepcopy or list comprehensions.

Provides a concise, readable way to repeat list elements, reducing boilerplate code.

Think of 'multiplying' a list like you multiply a string to repeat it.

When dealing with nested lists, remember that multiplication creates shallow copies; modifications to inner lists affect all copies.

Use [item for _ in range(n)] for deep copying or more complex transformations.