File Buffering
File Buffering
Files created with open() use buffering by default. The buffering parameter defines file buffering; buffering writes avoids frequent I/O resource use.
Buffering can improve writing efficiency. The buffering parameter has three settings:
- Full buffering (buffering > 1): I/O occurs when the standard I/O buffer fills. Reading and writing disk files are typical examples.
- Line buffering (buffering = 1): a newline in text I/O triggers output, as in line-buffered writing to a text file.
- No buffering (buffering = 0): I/O happens directly without retaining data in a buffer; this setting is supported only in binary mode.
To observe line buffering before closing, do not immediately leave a with statement: leaving it calls close(), which outputs the buffered content.
flush() forces the buffer to empty and outputs all buffered content. Closing a file stream with close() also flushes its buffer by default.
File buffering
import os
file = open(file="data.txt", mode="w", encoding="utf-8", buffering=1)
file.write("This is a test.")
os.system("pause")
file.flush()
os.system("pause")
file.close()Output: data.txt
This is a test.Send characters through a buffer
Unlock the complete interactive lab, deeper explanations, and curated reference answers.
KNOWLEDGE QUIZ
KNOWLEDGE QUIZ
When do the characters leave the buffer?
Use an idealized 8-byte full buffer with ASCII characters. Start with an empty file; write ABC, DE, FGH and IJ, then call flush(). List pending content, file output and transfer count after each step. Repeat with line buffering and unbuffered binary writes. No hidden automatic flushes occur in this model.
For line buffering, separately trace write('CAT'), write(' '), write('DOG'), close(). Does DOG need a newline before closing?