Has explorado cómo crear tus propios **administradores de contexto** y cómo utilizarlos en disposiciones anidadas y múltiples. Ahora deberás diseñar e implementar administradores de contexto personalizados que funcionen tanto de forma individual como conjunta, asegurando que los recursos se adquieran y liberen correctamente. Presta atención a cómo se gestionan las excepciones y cómo el orden de entrada y salida de los administradores de contexto afecta el comportamiento del programa.


import unittest
import user_code
import ast
import re   
import importlib
import csv
import unittest
import importlib
import io
from contextlib import redirect_stdout

class TestTask(unittest.TestCase):
    def test_manager_a_enter_exit(self):
        import user_code
        importlib.reload(user_code)
        f = io.StringIO()
        with redirect_stdout(f):
            a = user_code.ManagerA()
            a.__enter__()
            a.__exit__(None, None, None)
        output = normalize_text(f.getvalue())
        _dynamic_test(
            self,
            "entering managera" in output and "exiting managera" in output,
            "ManagerA prints enter and exit messages",
            f"ManagerA missing enter/exit messages: {output}"
        )

    def test_manager_b_enter_exit(self):
        import user_code
        importlib.reload(user_code)
        f = io.StringIO()
        with redirect_stdout(f):
            b = user_code.ManagerB()
            b.__enter__()
            b.__exit__(None, None, None)
        output = normalize_text(f.getvalue())
        _dynamic_test(
            self,
            "entering managerb" in output and "exiting managerb" in output,
            "ManagerB prints enter and exit messages",
            f"ManagerB missing enter/exit messages: {output}"
        )

    def test_nesting_order(self):
        import user_code
        importlib.reload(user_code)
        f = io.StringIO()
        with redirect_stdout(f):
            with user_code.ManagerA():
                with user_code.ManagerB():
                    pass
        output = normalize_text(f.getvalue())
        # Should be: Entering ManagerA, Entering ManagerB, Exiting ManagerB, Exiting ManagerA
        idx_enter_a = output.find("entering managera")
        idx_enter_b = output.find("entering managerb")
        idx_exit_b = output.find("exiting managerb")
        idx_exit_a = output.find("exiting managera")
        correct_order = (
            idx_enter_a != -1 and
            idx_enter_b != -1 and
            idx_exit_b != -1 and
            idx_exit_a != -1 and
            idx_enter_a < idx_enter_b < idx_exit_b < idx_exit_a
        )
        _dynamic_test(
            self,
            correct_order,
            "Nesting order is correct: ManagerA enters before ManagerB, ManagerB exits before ManagerA",
            f"Incorrect nesting order: {output}"
        )

    def test_multiple_with_order(self):
        import user_code
        importlib.reload(user_code)
        f = io.StringIO()
        with redirect_stdout(f):
            with user_code.ManagerA(), user_code.ManagerB():
                pass
        output = normalize_text(f.getvalue())
        # Should be: Entering ManagerA, Entering ManagerB, Exiting ManagerB, Exiting ManagerA
        idx_enter_a = output.find("entering managera")
        idx_enter_b = output.find("entering managerb")
        idx_exit_b = output.find("exiting managerb")
        idx_exit_a = output.find("exiting managera")
        correct_order = (
            idx_enter_a != -1 and
            idx_enter_b != -1 and
            idx_exit_b != -1 and
            idx_exit_a != -1 and
            idx_enter_a < idx_enter_b < idx_exit_b < idx_exit_a
        )
        _dynamic_test(
            self,
            correct_order,
            "Multiple context manager order is correct: ManagerA enters before ManagerB, ManagerB exits before ManagerA",
            f"Incorrect order for multiple context managers: {output}"
        )

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

Un análisis profundo de conceptos avanzados de programación estructural en Python, enfocado en el manejo robusto de archivos, gestión de errores, concurrencia, programación asíncrona y pruebas.

Domina el sistema de excepciones de Python para un manejo de errores y depuración robustos.

Explora técnicas avanzadas para operaciones de archivos y gestión de recursos utilizando gestores de contexto.

Comparación y aplicación de los módulos de multithreading y multiprocessing de Python para la programación concurrente.

Domina la programación asíncrona en Python utilizando la biblioteca asyncio para aplicaciones escalables dependientes de E/S.

Explora cómo escribir, organizar y ejecutar pruebas utilizando los frameworks unittest y pytest de Python.

Desafío: Apilamiento de Gestores de Contexto

Solución