assert True

Testing Patterns

Meaning

Used to assert that a condition is true during development; raises an AssertionError if the condition is false. It helps catch programming errors early and documents assumptions that must hold at that point in the code.

Primary Function

Debugging

Communicative Purpose

Validate assumptions and catch programming errors early.

Pattern

assert ;

Core Structure

assert ;

Função primária

Debugging

Propósito comunicativo

Validate assumptions and catch programming errors early.

Situações de gatilho

Checking preconditions at the start of a function, verifying invariants after a computation, debugging during development.

Contextos

Python scripts, libraries, unit tests, and debugging sessions.

Padrão

assert ;

Estrutura central

assert ;

Slots de substituição

condition: boolean expression

Colocados típicos

try/except blocks
logging statements
unit test frameworks

Substituições comuns

assert False
assert 1 == 1
assert variable is not None

Erros comuns

Using assert for data validation in production (can be disabled with -O), forgetting parentheses, relying on side effects in the condition.

Similar / contraste

raise Exception (explicit error raising) vs assert (debugging aid); using if statements for control flow rather than assertions.

Interferências

Coming from languages like C or Java where assert is a macro that may be disabled in release builds; in Python assert is a statement that can be globally disabled with the -O optimization flag.

Família do chunk

assert statements
precondition checks
defensive programming
design-by-contract

Nuance

Assertions can be disabled globally with Python's -O flag, so they should not be used for enforcing business rules or validating untrusted input in production code.

Efeito pragmático

Catches bugs early during development and makes assumptions explicit in the source code.

Dica de memória

Think 'assert' as 'assert my assumption holds true here'.

Nota

Assertions are statements, not functions, and do not return a value; they are removed when Python is run with the -O optimization flag.

Upgrade path

Using unittest's assertEqual, assertTrue, or pytest's richer assertion syntax for more informative test failures.

Frequência: MediumFormulaicidade: Semi-fixedTipo de construção: assert statementPrioridade de aquisição: Active recallPrioridade de output: BothTag de espaçamento: Medium-term

Examples

def factorial(n): assert isinstance(n, int) and n >= 0, "n must be a non-negative integer" result = 1 for i in range(2, n + 1): result *= i return result print(factorial(5))

data = [1, 2, 3, 4] for x in data: assert isinstance(x, int), f"Non-int found: {x}" print(x * 2)

def add(a, b): return a + b assert add(2, 3) == 5 assert add(-1, 1) == 0 print("All tests passed")