Assignment 4 — Python Programming Solutions

Python 3.x  |  No third-party dependencies  |  Windows / macOS / Linux

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Table of Contents

1. Project Structure
2. Question 1 — Execute OS Commands
3. Question 2 — Project Euler Problems
4. Screenshots

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Project Structure

Assignment-4/
│
├── README.md
├── Screenshots/                        ← proof of working output
│   ├── Q1-Execute-Commands-1.png       ← demo mode (--demo flag)
│   ├── Q1-Execute-Commands-2.png       ← custom commands + duplicate skip
│   └── Q2-Euler-Problems.png           ← both Euler answers
│
├── Q1-Execute-Commands/
│   ├── run_commands.py                 ← CLI entry point
│   └── command_runner/
│       ├── __init__.py
│       └── executor.py                 ← core execution logic
│
└── Q2-Euler-Problems/
    ├── run_all.py                      ← CLI entry point
    └── euler_problems/
        ├── __init__.py
        ├── problem_065.py              ← Convergents of e
        └── problem_315.py             ← Digital root clocks

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Question 1 — Execute OS Commands

Problem Statement

Write a Python program that executes a given list of OS commands and returns the results as a list of dictionaries with the following rules:

• Duplicates — each command is run only once (order preserved)
• Failures — if a command fails, execution continues for remaining commands
• Output format — a JSON list of { command: { output, error, status } } dicts

How It Works

Module	Role
command_runner/executor.py	Runs each command via subprocess, captures stdout/stderr, handles timeouts and OS errors
command_runner/__init__.py	Package exports
run_commands.py	CLI — supports positional args, --file, --demo, and --timeout flags

Running Q1

Navigate to the folder:

cd "c:\Users\rehan.farooque\Downloads\Assignment-4\Q1-Execute-Commands"

Demo mode (built-in commands including a duplicate and a failing command):

python run_commands.py --demo

Pass commands directly:

python run_commands.py "echo hello" "python --version" "no-such-cmd"

With custom timeout (seconds):

python run_commands.py --demo --timeout 10

Expected Output

[
  {
    "python --version": {
      "output": "Python 3.x.x",
      "error": "",
      "status": "success"
    }
  },
  {
    "echo Hello from the command runner": {
      "output": "Hello from the command runner",
      "error": "",
      "status": "success"
    }
  },
  {
    "no-such-command-xyz": {
      "output": "",
      "error": "'no-such-command-xyz' is not recognized as an internal or external command,\noperable program or batch file.",
      "status": "Failed"
    }
  }
]

Note: The duplicate echo Hello from the command runner in the demo list is silently skipped — only one entry appears in the output.

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Question 2 — Project Euler Problems

Problem 65 — Convergents of e

Problem: The continued fraction expansion of e is:

e = [2; 1, 2, 1, 1, 4, 1, 1, 6, 1, 1, 8, ...]

The convergents $p_n / q_n$ satisfy:

$$p_n = a_n \cdot p_{n-1} + p_{n-2}$$

Find the sum of digits in the numerator of the 100th convergent of e.

Answer: 272

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Problem 315 — Digital Root Clocks

Problem: Sam and Max each build a digital-root clock. When fed a number, the clock shows the number, then each digit-sum step, until a single digit remains, then goes blank.

Example: 137  →  11  →  2  →  (blank)

7-segment display — each digit uses some of 7 segments (top, top-right, bottom-right, bottom, bottom-left, top-left, middle). Energy is consumed only when segments switch on or off.

Clock	Behaviour	Cost
Sam's	Turns the entire panel OFF, then ON for each number	2 × segments per number
Max's	Only toggles segments that actually change	XOR of consecutive segment states

Worked example (n = 137):

Step	Sam's cost	Max's cost
137 on/off	(2+5+4) × 2 = 22	11 (on) + 7 (→11 XOR)
11 on/off	(2+2) × 2 = 8	0 (already set) + 3 (→2 XOR)
2 on/off	5 × 2 = 10	4 (on) + 5 (off)
Total	40	30

Difference for 137: 10

The program sums this difference over all primes between 10,000,000 and 20,000,000.

Answer: 13625242

How It Works

Module	Role
euler_problems/problem_065.py	Continued fraction recurrence for e, digit sum of numerator
euler_problems/problem_315.py	Sieve of Eratosthenes, 7-segment encoding, Sam vs Max cost calculation
run_all.py	CLI runner with timing for both problems

Running Q2

Navigate to the folder:

cd "c:\Users\rehan.farooque\Downloads\Assignment-4\Q2-Euler-Problems"

Run both problems:

python run_all.py

Run a single problem:

python run_all.py 65
python run_all.py 315

Expected Output

--- Project Euler Problem 65 ---
Sum of digits in numerator of 100th convergent of e
Answer : 272
Elapsed: 0.00s

--- Project Euler Problem 315 ---
Sam - Max segment switches for primes in [10^7, 2*10^7)
Answer : 13625242
Elapsed: 5.72s

Note: Problem 315 sieves primes up to 20 million — expect ~5-10 seconds runtime.

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Screenshots

Q1 — Execute OS Commands

Demo mode (python run_commands.py --demo) — shows python --version (success), echo (success), duplicate skipped, and no-such-command-xyz (Failed):

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Custom commands (python run_commands.py "echo hello" "pwd" "echo hello" "no-such-cmd") — demonstrates duplicate skipping (echo hello appears once) and graceful failure handling:

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Q2 — Project Euler Problems

Problem 65 (python run_all.py 65) — Answer: 272 (instantaneous) Problem 315 (python run_all.py 315) — Answer: 13625242 (~5 seconds):

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Requirements

• Python 3.10+ (uses bit_count() method and match patterns)
• No external packages required — standard library only (subprocess, functools, argparse, json, time)