Meaning
Reads the entire contents of an open file object into a list where each element is a line, including the newline character. This avoids the overhead of repeated file reads and provides immediate random access for processing. Use when you need random access to lines after loading them, such as for multiple passes or line-number based operations.
Primary Function
File I/O
Communicative Purpose
Load a complete text file into memory as a list of strings.
Pattern
result_var = file_obj.readlines()
Core Structure
... = ....readlines()
Função primária
File I/O
Propósito comunicativo
Load a complete text file into memory as a list of strings.
Situações de gatilho
File processing: when you need to process a file multiple times, File processing: when you need line numbers for error reporting, File processing: when you want to slice or index specific lines.
Contextos
General Python scripts, data‑processing pipelines, configuration loaders, test fixtures.
Padrão
result_var = file_obj.readlines()
Estrutura central
... = ....readlines()
Slots de substituição
result_var: identifier, file_obj: file‑like object
Colocados típicos
- with open('path') as f
- for line in lines
- list comprehension over lines
Substituições comuns
- list(f)
- f.read().splitlines()
- for line in f: (lazy iteration)
Erros comuns
Leaving the file open, reading huge files into memory, forgetting that newline characters remain, using readlines() on binary streams without decoding.
Similar / contraste
f.read() returns a single string; f.readline() returns one line; iterating over f yields lines lazily.
Interferências
Coming from Java: may expect readLines() to return an iterator rather than a list → use direct iteration over the file object for lazy processing or list(f) for a list.
Família do chunk
- File I/O
- iterator consumption
- list conversion
Nuance
Do not use for files that are too large to fit comfortably in memory, as it loads the entire file into RAM. Consumes memory proportional to file size, which can cause slowdowns or out-of-memory errors on huge files. Be aware that trailing newlines are preserved and binary files require decoding before calling readlines().
Efeito pragmático
Provides random access to any line and simplifies downstream list operations, but can increase memory consumption.
Dica de memória
Like grabbing every page of a book and stacking them on your desk so you can flip to any page instantly.
Nota
Each element retains its trailing newline unless stripped.
Upgrade path
lines = Path('file.txt').read_text().splitlines() # pathlib shortcut, no explicit open/close
Log in to save chunks.