How Often Does Python Flush Files: Unbuffered, Line Buffered, or Custom Buffering?

Python File Flushing Frequency Unveiled

Understanding how Python handles flushing is crucial for effective file operations. By default, Python utilizes the operating system's default buffering strategy for file operations. However, you have the flexibility to specify specific buffering settings.

When working with files, you can customize three main buffering options:

1. Unbuffered (0): Data is flushed after each write operation without any buffering.
2. Line Buffered (1): Data is flushed after a newline character is encountered.
3. Buffer Size: You can specify a fixed buffer size in bytes. Data is flushed when the buffer is full.

For stdout, Python follows line buffering by default. However, if you redirect stdout to a file using techniques like sys.stdout.flush(), the flushing behavior depends on the buffering settings of the underlying file.

For instance, if the output file is configured with line buffering, flushing will occur after each newline, just as it does for stdout. On the other hand, if the output file is set to unbuffered, flushing will happen after every write operation.

Specifying a specific buffer size allows you to tailor flushing behavior to suit your specific requirements. However, leaving the buffering argument unspecified results in the operating system's default settings being applied, which usually translates to line buffering for terminal devices and full buffering for other file types.

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