Meaning
Checks whether a collection (like a list) has at least one element by comparing its length to zero. Used when you need to ensure the collection is not empty before processing.
Primary Function
Condition checking
Communicative Purpose
Determine if a container is non-empty to guard subsequent operations.
Pattern
len(items) > 0
Core Structure
len(...) > 0
Função primária
Condition checking
Propósito comunicativo
Determine if a container is non-empty to guard subsequent operations.
Situações de gatilho
Before iterating over a list to avoid errors; when processing user input that may be empty; when checking results of a function that returns a list.
Contextos
Python codebases, data processing scripts, web backends, any situation where lists are used.
Padrão
len(items) > 0
Estrutura central
len(...) > 0
Slots de substituição
The variable or expression whose length is to be checked (e.g., a list, string, etc.).
Colocados típicos
- Often used with `if` statements
- followed by processing loops or function calls.
Substituições comuns
- Direct truthiness test (`if fruits:`)
- using `any()` for iterables
- checking `len(...) != 0`.
Erros comuns
Confusing `len(fruits) > 0` with `len(fruits) >= 1` (same), but forgetting that empty strings also have length 0; using `is not []` incorrectly.
Similar / contraste
`if not fruits:` to check for emptiness (opposite); `if fruits:` for truthiness (more Pythonic).
Interferências
Coming from languages where length check is required (e.g., C), may overlook Python's direct truthiness evaluation.
Família do chunk
- len_check
- truthiness_check
- any_check
Nuance
Works for any sized object with `__len__`; for generators, `len` raises TypeError; better to use iteration or `any()`.
Efeito pragmático
Prevents errors from operating on empty collections; makes intent explicit.
Dica de memória
Think 'length greater than zero' as 'has items'.
Nota
Avoid this pattern with generators, as `len` raises TypeError; prefer iteration or `any()` when the source may be lazy.
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