Python sys Module Programs with Solutions

20 sys module programs: command-line arguments, exit codes, stdin/stdout/stderr, the module search path, version checks, recursion limits and object sizes. Programs that need arguments run a small helper script so you can see real results.

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• #1Read command-line arguments
  Write a Python program that prints its command-line arguments.Easy
• #2Sum numbers from the command line
  Write a Python program that adds the numbers passed as arguments.Easy
• #3Exit with a status code
  Write a Python program that exits with code 1 on failure and show the code the caller sees.Easy
• #4Check the Python version
  Write a Python program that checks it is running on Python 3.10 or newer.Easy
• #5Detect the operating system
  Write a Python program that prints a different message per operating system.Easy
• #6Write errors to stderr
  Write a Python program that writes normal output to stdout and errors to stderr.Easy
• #7Read numbers from stdin
  Write a Python program that reads numbers from standard input and prints their total.Easy
• #8Write with sys.stdout
  Write a Python program that prints a progress bar with sys.stdout.write.Easy
• #9Inspect sys.path
  Write a Python program that shows how many folders Python searches for modules.Easy
• #10Import from a custom folder
  Write a Python program that adds a folder to sys.path and imports a module from it.Medium
• #11Which modules are loaded?
  Write a Python program that checks whether a module has been imported yet.Easy
• #12Size of objects
  Write a Python program that compares the memory size of a few objects.Easy
• #13Recursion limit
  Write a Python program that reads the recursion limit and handles RecursionError.Easy
• #14Largest list index
  Write a Python program that prints sys.maxsize and shows ints can be bigger.Easy
• #15Float limits
  Write a Python program that prints the largest float and float precision.Easy
• #16Which Python is running?
  Write a Python program that checks which interpreter file is running.Easy
• #17Byte order and encoding
  Write a Python program that prints the machine’s byte order and the default text encoding.Easy
• #18Exit with a message
  Write a Python program that stops with a message when a required file is missing.Easy
• #19Arguments with argparse
  Write a Python program that parses named options with argparse.Medium
• #20Current exception info
  Write a Python program that reads the active exception with sys.exception().Easy

Current exception info

Write a Python program that reads the active exception with sys.exception().

KeyError 'missing'

Approach

1. Inside except, sys.exception() returns the exception being handled (Python 3.11+).

Solution

import sys try:    {}["missing"]except KeyError:    e = sys.exception()    print(type(e).__name__, e)

KeyError 'missing'

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Validate email addresses

Write a Python program to check which strings are valid email addresses.

asha@sqatools.in       True
ravi.k+qa@mail.co.uk   True
bad@                   False
no space@x.com         False

Approach

1. re.fullmatch with a practical email pattern.

Solution

import re pattern = re.compile(r"[\w.+-]+@[\w-]+(\.[\w-]+)+")for e in ["asha@sqatools.in", "ravi.k+qa@mail.co.uk", "bad@", "no space@x.com"]:    print(e.ljust(22), bool(pattern.fullmatch(e)))

asha@sqatools.in       True
ravi.k+qa@mail.co.uk   True
bad@                   False
no space@x.com         False

Line by line

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Arguments with argparse

Write a Python program that parses named options with argparse.

smoke firefox 2

Approach

1. Pass a list to parse_args to test without a terminal.

Solution

import argparse parser = argparse.ArgumentParser(description="Run tests")parser.add_argument("suite")parser.add_argument("--browser", default="chromium", choices=["chromium", "firefox", "webkit"])parser.add_argument("--retries", type=int, default=0) args = parser.parse_args(["smoke", "--browser", "firefox", "--retries", "2"])print(args.suite, args.browser, args.retries)

smoke firefox 2

Line by line

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Exit with a message

Write a Python program that stops with a message when a required file is missing.

1 config.ini not found

Approach

1. sys.exit("message") prints the message to stderr and exits with code 1.

Solution

import subprocessimport sys code = "import os, sys\nif not os.path.exists('config.ini'):\n    sys.exit('config.ini not found')"r = subprocess.run([sys.executable, "-c", code], capture_output=True, text=True)print(r.returncode, r.stderr.strip())

1 config.ini not found

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Which Python is running?

Write a Python program that checks which interpreter file is running.

True
True -> not in a virtual environment

Approach

1. sys.executable.

Solution

import osimport sys print(os.path.basename(sys.executable).lower().startswith("python"))print(sys.prefix == sys.base_prefix, "-> not in a virtual environment" if sys.prefix == sys.base_prefix else "-> in a virtual environment")

True
True -> not in a virtual environment

Line by line

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Byte order and encoding

Write a Python program that prints the machine’s byte order and the default text encoding.

little
utf-8

Approach

1. sys.byteorder and sys.getdefaultencoding().

Solution

import sys print(sys.byteorder)print(sys.getdefaultencoding())

little
utf-8

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Largest list index

Write a Python program that prints sys.maxsize and shows ints can be bigger.

True
True

Approach

1. sys.maxsize limits sizes, not integer values.

Solution

import sys print(sys.maxsize == 2 ** 63 - 1)print(sys.maxsize + 1 > sys.maxsize)

True
True

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Float limits

Write a Python program that prints the largest float and float precision.

1.7976931348623157e+308
15 decimal digits of precision

Approach

1. sys.float_info.

Solution

import sys print(sys.float_info.max)print(sys.float_info.dig, "decimal digits of precision")

1.7976931348623157e+308
15 decimal digits of precision

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Recursion limit

Write a Python program that reads the recursion limit and handles RecursionError.

1000
RecursionError caught

Approach

1. sys.getrecursionlimit().

Solution

import sys print(sys.getrecursionlimit()) def dive(n):    return dive(n + 1) try:    dive(0)except RecursionError:    print("RecursionError caught")

1000
RecursionError caught

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