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Python Time & Space Complexity

Fcntl

fcntl Module¶

The fcntl module provides access to file control operations on Unix, including file locking and other low-level file I/O control.

Complexity Reference¶

Operation	Time	Space	Notes
`flock()`	O(1)	O(1)	Acquire lock; blocks if contended (without LOCK_NB)
`fcntl()`	O(1)	O(1)	File control operation

File Locking and Control¶

File Locking¶

import fcntl

# Open file
with open('data.txt', 'w') as f:
    # Acquire lock - O(1)
    fcntl.flock(f.fileno(), fcntl.LOCK_EX)

    try:
        # Write while locked
        f.write('Protected data')
    finally:
        # Release lock - O(1)
        fcntl.flock(f.fileno(), fcntl.LOCK_UN)

Non-blocking Lock¶

import fcntl

with open('file.txt', 'r') as f:
    try:
        # Non-blocking exclusive lock - O(1)
        fcntl.flock(f.fileno(), fcntl.LOCK_EX | fcntl.LOCK_NB)
        print("Lock acquired")
    except BlockingIOError:
        print("File is locked by another process")