Programming Course — Laboratory Works

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Author: Eva Makarova
Programming Language: Python 3
Operating System: Windows

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Table of Contents

1. Laboratory Work 1. Decorators and Asynchronous Programming
2. Laboratory Work 2. Asynchrony and Multithreading
3. Laboratory Work 3. Working with the os Library
4. Laboratory Work 4. Introduction to ORM & SQLAlchemy
5. Tests

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Laboratory Work 1. Decorators and Asynchronous Programming

Tasks:

• Task 1 — Parameterless Decorator (logger): Implementation of a logger decorator that outputs the function name, its arguments, return value, and execution time.
• Task 2 — Parameterized Decorator (retry): Implementation of a retry(attempts, delay, exceptions=None) decorator that retries function execution upon encountering errors specified in exceptions for a given number of attempts with a delay of delay seconds.
• Task 3 — Parameterless Class Decorator (logger): A class decorator that logs the class name, methods (including magic methods), arguments, and execution time. Added a show_magic_methods flag to toggle logging of magic methods.
• Task 4 — Parameterized Class Decorator (call_limiter): Implementation of a call_limiter(limit) decorator that restricts the number of invocations for each class method to limit times.
• Task 5 — Introduction to Asynchrony: Implementation of two asynchronous functions with asyncio.sleep() intervals to demonstrate non-blocking execution.

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Laboratory Work 2. Asynchrony and Multithreading

Tasks:

• Task 1 — Basic Asynchronous Functions: An asynchronous function that waits for delay seconds and outputs a message.
• Task 2 — Concurrent Execution with asyncio.gather: Execution of three concurrent tasks with different delays (2, 1, and 3 seconds) and distinct text outputs.
• Task 3 — Synchronous vs. Asynchronous API Requests: Performance comparison between sequential HTTP requests via requests and asynchronous requests using aiohttp to external web resources. Execution time measurement and response ordering analysis.
• Task 4 — Working with Threads (threading): Comparison between sequential function calls with a delay and its parallel execution across 3 separate threads.
• Task 5 — Data Race Condition: Demonstration of a race condition during improper concurrent increments of a shared global variable from multiple threads.
• Task 6 — Resolving the Data Race Condition: Application of the threading.Lock synchronization primitive to protect the critical section and prevent data races.

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Laboratory Work 3. Working with the os Library

Objective: Exploring systemic capabilities of the os library without using external command shells (cmd, bash).

Tasks:

• Task 1 — File Operations Script:
  • Validating and adjusting the current working directory.
  • Creating a file, writing data, and verifying existence via os.path.
  • Retrieving file size, last access time, and modification time.
  • Fetching the system's current username.
  • Reading and modifying file access permissions (os.chmod).
• Task 2 — Directory Operations Script:
  • Copying, renaming, and moving files across nested directories using os methods.
  • Moving and renaming a file in a single operation.
  • Recursive traversal and display of directory trees and files (os.walk).
  • Creating and removing temporary and nested folders.
• Task 3 — System Management Script (Interactive Manager): A console-based interactive menu providing the following functionality:
  • a) List of all running processes;
  • b) Detailed information about a specific process;
  • c) Process termination by PID;
  • d) Viewing and updating environment variables (os.environ);
  • e) Modifying process priority;
  • f) Displaying system information;
  • g) Exit.
  • Exception handling for missing permissions (PermissionError).

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Laboratory Work 4. Introduction to ORM & SQLAlchemy

Objective: Using SQLAlchemy ORM to design data models, relationships, and execute CRUD operations for a basic book reservation system.

Entities and DB Schema:

• User: id (PK), name (Not Null), email (Unique, Not Null).
• Book: id (PK), title (Not Null), author (Not Null), copies_available (Integer).
• Booking: id (PK), user_id (FK → User.id), book_id (FK → Book.id), booking_date (Date).

Implemented Features:

1. Setting up SQLite / PostgreSQL connections inside a Docker container.
2. Database table creation via Base.metadata.create_all().
3. Inserting new users and books into the database.
4. Creating a booking with an automatic reduction of copies_available.
5. Canceling/deleting a booking with a corresponding increase in available copies.