linecache retrieves a particular line without making every caller manage repeated file reads. It supports parts of traceback and tools that display source-code context.
Retrieve a particular line
import linecache
from pathlib import Path
from tempfile import TemporaryDirectory
with TemporaryDirectory() as folder:
path = Path(folder, "sample.py")
path.write_text("first = 1\nsecond = 2\n", encoding="utf-8")
assert linecache.getline(str(path), 2) == "second = 2\n"
linecache.clearcache()Understand silent failures
getline() returns an empty string for a missing line or many read failures rather than exposing those exceptions. If an application must distinguish a missing file from an invalid line, validate the path and range separately.
Refresh after file changes
Call checkcache(filename) when another process or part of the program may modify a file. clearcache() drops every entry. Do not use this module as general storage or assume freshness without an invalidation policy.
Keep learning
Continue with debugging Python with PDB. The official Python documentation, accessed July 22, 2026, covers getline, invalidation, and module-loader support.