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Python Time & Space Complexity

Cmd

cmd Module¶

The cmd module provides a framework for building line-oriented interactive command interpreters.

Complexity Reference¶

Operation	Time	Space	Notes
`Cmd()` init	O(1)	O(1)	Create interpreter
Parse command	O(n)	O(n)	n = input length
Command dispatch	O(1)	O(1)	Call handler

Building Interactive Shells¶

Simple Command Interpreter¶

import cmd

class MyShell(cmd.Cmd):
    """Simple command interpreter"""

    prompt = "myshell> "

    def do_hello(self, arg):
        """Say hello"""
        print(f"Hello {arg}!")

    def do_exit(self, arg):
        """Exit shell"""
        return True

# Run shell - O(m)
shell = MyShell()
shell.cmdloop()

# User can type:
# hello world
# exit

Advanced Commands¶

import cmd

class AdvancedShell(cmd.Cmd):
    def do_add(self, arg):
        """Add two numbers: add 3 5"""
        try:
            parts = arg.split()
            result = int(parts[0]) + int(parts[1])
            print(f"Result: {result}")
        except (ValueError, IndexError):
            print("Usage: add <int> <int>")

    def help_add(self):
        print("Add two integers together")

shell = AdvancedShell()
shell.onecmd("add 10 20")  # Result: 30