In this challenge, you will apply advanced file handling techniques in Python to update and manage a weather log. You will use different file modes - such as write (`"w"`), append (`"a"`), read and write (`"r+"`), and read (`"r"`) - to perform specific operations on the same file. 


import unittest
import user_code
import ast
import re   
import importlib
import csv
import unittest
import os

class TestTask(unittest.TestCase):
    def setUp(self):
        # Remove the file before every test to ensure clean state
        if os.path.exists("weather_log.txt"):
            os.remove("weather_log.txt")

    def tearDown(self):
        if os.path.exists("weather_log.txt"):
            os.remove("weather_log.txt")

    def test_file_created_and_header_written(self):
        import importlib
        import user_code
        importlib.reload(user_code)
        exists = os.path.exists("weather_log.txt")
        _dynamic_test(
            self,
            exists,
            "File 'weather_log.txt' was created.",
            "File 'weather_log.txt' was not created."
        )
        with open("weather_log.txt", "r") as f:
            first_line = f.readline().strip()
        _dynamic_test(
            self,
            first_line.startswith("Status: "),
            "Header line exists in file.",
            f"Header line missing or malformed: '{first_line}'"
        )

    def test_monday_and_tuesday_lines_appended(self):
        import importlib
        import user_code
        importlib.reload(user_code)
        with open("weather_log.txt", "r") as f:
            lines = f.readlines()
        _dynamic_test(
            self,
            len(lines) >= 3,
            "At least three lines exist in the file (header + 2 days)",
            f"Expected at least 3 lines, got {len(lines)}"
        )
        monday = lines[1].strip() if len(lines) > 1 else ""
        tuesday = lines[2].strip() if len(lines) > 2 else ""
        _dynamic_test(
            self,
            monday == "Monday: 22°C, Sunny",
            "Monday line correctly appended.",
            f"Monday line incorrect or missing: '{monday}'"
        )
        _dynamic_test(
            self,
            tuesday == "Tuesday: 19°C, Rainy",
            "Tuesday line correctly appended.",
            f"Tuesday line incorrect or missing: '{tuesday}'"
        )

    def test_header_updated(self):
        import importlib
        import user_code
        importlib.reload(user_code)
        with open("weather_log.txt", "r") as f:
            first_line = f.readline().strip()
        _dynamic_test(
            self,
            first_line == "Status: Updated.",
            "Header correctly updated to 'Status: Updated.'",
            f"Header not updated. Found: '{first_line}'"
        )

    def test_final_content(self):
        import importlib
        import user_code
        importlib.reload(user_code)
        with open("weather_log.txt", "r") as f:
            content = f.read()
        expected = "Status: Updated.\\nMonday: 22°C, Sunny\\nTuesday: 19°C, Rainy\\n"
        _dynamic_test(
            self,
            normalize_text(content) == normalize_text(expected),
            "File content matches expected final output.",
            f"File content does not match expected.\\nExpected:\\n{expected}\\nGot:\\n{content}"
        )

def _dynamic_test(test_case, condition, success_message, failure_message):
    if condition:
        test_case._testMethodName = success_message
        test_case.assertTrue(True, success_message)
    else:
        test_case._testMethodName = failure_message
        test_case.fail(failure_message)

def normalize_text(text):
    text = text.lower()
    text = re.sub(r"\\s{2,}", " ", text)
    text = re.sub(r"\\s*([,:?])\\s*", r"\\1 ", text)
    return text.strip()

def change_var(code: str, var_name: str, value: str) -> str:
    tree = ast.parse(code)
    lines = code.splitlines()
    changed = False
    # Collect all assignment nodes to modify
    assign_nodes = [
        (i, node)
        for i, node in enumerate(tree.body)
        if isinstance(node, ast.Assign)
        and any(isinstance(target, ast.Name) and target.id == var_name for target in node.targets)
    ]

    # If nothing to change, return unmodified code
    if not assign_nodes:
        return code

    # Perform replacements for all matching assignments (from last to first to not break line offsets)
    for i, node in reversed(assign_nodes):
        start_line = node.lineno - 1
        line = lines[start_line]
        indent = ' ' * (len(line) - len(line.lstrip()))
        lines[start_line] = f"{indent}{var_name} = {value}"
        next_line = len(lines)
        for next_node in tree.body[i+1:]:
            if hasattr(next_node, 'lineno'):
                next_line = next_node.lineno - 1
                break
        if next_line > start_line + 1:
            lines[start_line+1:next_line] = []
        changed = True

    return '\\n'.join(lines) if changed else code

if __name__ == "__main__":
    unittest.main()


test_main.py

A deep dive into advanced structural programming concepts in Python, focusing on robust file handling, error management, concurrency, asynchronous programming and testing.

Master Python's exception system for robust error handling and debugging.

Explore advanced techniques for file operations and resource management using context managers.

Compare and apply Python's multithreading and multiprocessing modules for concurrent programming.

Master asynchronous programming in Python using the asyncio library for scalable I/O-bound applications.

Explore how to write, organize, and run tests using Python's unittest and pytest frameworks.

Challenge: Weather Log Update

Solution