Benutzerdefinierte Ausnahmen ermöglichen die Definition von Fehlertypen, die bestimmte Probleme im Code beschreiben. In Python wird eine benutzerdefinierte Ausnahme durch das Subklassifizieren von `Exception` erstellt. Die Ausnahme wird mit `raise` ausgelöst, wenn eine bestimmte Bedingung erfüllt ist, und mit einem `try-except`-Block behandelt.

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_custom_exception_exists(self):
        import user_code
        importlib.reload(user_code)
        exc = getattr(user_code, 'NegativeNumberError', None)
        _dynamic_test(
            self,
            exc is not None and issubclass(exc, Exception),
            "NegativeNumberError class is defined and inherits from Exception",
            "NegativeNumberError class not found or does not inherit from Exception."
        )

    def test_function_returns_positive(self):
        import user_code
        importlib.reload(user_code)
        func = getattr(user_code, 'check_positive_number', None)
        _dynamic_test(
            self,
            callable(func),
            "check_positive_number function is defined",
            "check_positive_number function is not defined."
        )
        result = func(10)
        _dynamic_test(
            self,
            result == 10,
            "Function returns the positive number unchanged",
            f"Expected 10, got {result}"
        )

    def test_function_returns_zero(self):
        import user_code
        importlib.reload(user_code)
        func = getattr(user_code, 'check_positive_number', None)
        result = func(0)
        _dynamic_test(
            self,
            result == 0,
            "Function returns zero unchanged",
            f"Expected 0, got {result}"
        )

    def test_function_raises_on_negative(self):
        import user_code
        importlib.reload(user_code)
        func = getattr(user_code, 'check_positive_number', None)
        exc = getattr(user_code, 'NegativeNumberError', None)
        raised = False
        try:
            func(-5)
        except Exception as e:
            raised = isinstance(e, exc)
        _dynamic_test(
            self,
            raised,
            "Function raises NegativeNumberError for negative input",
            "Function did not raise NegativeNumberError for negative input."
        )

    def test_print_output(self):
        import user_code
        importlib.reload(user_code)
        f = io.StringIO()
        with redirect_stdout(f):
            importlib.reload(user_code)
        output = normalize_text(f.getvalue())
        _dynamic_test(
            self,
            "number must be non-negative" in output,
            "Output includes exception message for negative input",
            f"Expected exception message not found in output: {output}"
        )
        _dynamic_test(
            self,
            "3" in output,
            "Output includes result for positive input",
            f"Expected output for positive input (3) not found in output: {output}"
        )
        _dynamic_test(
            self,
            "0" in output,
            "Output includes result for zero input",
            f"Expected output for zero input (0) not found in output: {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
    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 not assign_nodes:
        return code
    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

Sie werden praktische Fähigkeiten in Pythons Modulen und Importen für effizientes Code-Management erwerben. Beherrschen Sie fortgeschrittene Fehlerbehandlungstechniken für zuverlässigere Anwendungen, automatisieren Sie Dateioperationen mit Dateiverwaltung und lernen Sie robuste Teststrategien mit Pytest und Unittest, um die Integrität Ihres Codes sicherzustellen.

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Challenge: Das Negative Abfangen

Lösung