Validation

Expresses that all items must satisfy a given predicate before proceeding

Data validation: ensure all numbers in a list are positive before processing; Unit testing: assert that a collection satisfies a predicate across test cases; Data pipeline: guard against invalid records during batch transformation

General Python scripts, data‑processing pipelines, scientific computing code, unit‑test suites, educational examples

assert all(condition for item in iterable)

assert all(... for ... in ...)

condition: expression involving the loop variable; iterable: expression yielding an iterable collection

• assert
• all
• generator expression
• for

• Using an explicit loop with if not condition: raise AssertionError
• using any(... ) for opposite checks
• employing list comprehensions with assert len([...]) == len(iterable)

Writing list comprehensions inside assert (creates an unnecessary list); forgetting the parentheses around the generator expression; relying on assert for runtime validation in production where the -O flag disables it

any(... for ...) – checks that at least one element satisfies the predicate; plain assert condition – validates a single boolean, not a collection; explicit loops with raise – more verbose but works even when asserts are stripped

Coming from languages without a built‑in all: developers may write a manual loop expecting the same brevity; from C/C++ where assert is a macro that cannot contain generator expressions

• assertion
• validation
• guard_clause
• generator_expression

Do not use for side‑effect checks; remember assert statements can be removed with the -O optimization flag, so they are unsuitable for mandatory validation in production code; generator expression evaluates lazily, which is efficient for large iterables

Catches invalid data early, making failures easier to locate and preventing downstream errors

All positive? Assert all

Assert statements are removed when Python is run with the -O optimization flag, so they should not be used for mandatory validation in production code.

def validate_positive(iterable): for i, x in enumerate(iterable): if x <= 0: raise ValueError(f"Element {i} is not positive: {x}") return iterable