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Python Time & Space Complexity

Readline

readline Module¶

The readline module provides line-editing support for Python's interactive interpreter, enabling command history and auto-completion.

Complexity Reference¶

Operation	Time	Space	Notes
Setup	O(1)	O(1)	Configure readline
Read line	O(n)	O(n)	n = input length

Interactive Line Editing¶

Using Readline¶

import readline

# Set up completion - O(1)
def completer(text, state):
    options = ['apple', 'apricot', 'banana']
    matches = [opt for opt in options if opt.startswith(text)]

    if state < len(matches):
        return matches[state]
    else:
        return None

readline.set_completer(completer)

# Parse bindings - O(1)
readline.parse_and_bind('tab: complete')

# In interactive mode, user can:
# >>> inp = input("Enter: ")  # Has history and completion

History Management¶

import readline

# Read history - O(n)
readline.read_history_file('.python_history')

# Add to history - O(1)
readline.add_history('print("test")')

# Save history - O(n)
readline.write_history_file('.python_history')