Python Linecache Module
The linecache module allows you to get any line from a Python source file, while attempting to optimize internally using a cache, which is common when many lines are read from a single file. This is used by the traceback module to retrieve source lines for formatted stack traces.
Importing the Module
import linecacheReading Lines
The linecache.getline() function retrieves a specific line from a file.
import linecache
import os
# Create a dummy file
filename = 'example_script.py'
with open(filename, 'w') as f:
f.write('def func():\n return "Hello"\n\nprint(func())')
# Get the 2nd line
line = linecache.getline(filename, 2)
print(f"Line 2: {line.strip()}")
# Output: Line 2: return "Hello"If the filename cannot be found or the line number is invalid, it returns an empty string.
Managing the Cache
The module stores file content in memory. You might need to manage this cache.
clearcache()
Clears the cache. Use this if you no longer need the data read from files previously.
linecache.clearcache()checkcache()
Check the cache for validity. Use this if files on disk might have changed, and you want the updated version.
linecache.checkcache(filename)Lazy Loading
The lazycache() function allows you to capture information about a non-file-based module to permit getting its lines later via getline().