Teachers often want to make students feel welcome at the start of the year. Sending a personalized message to each student is a great way to build a positive classroom environment. In this challenge, you will use your knowledge of **strings** and **lists** to generate a warm welcome for every student in your class.


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_prints_message_for_each_student(self):
        import user_code
        importlib.reload(user_code)
        students = ["Alice", "Ben", "Carlos"]
        f = io.StringIO()
        with redirect_stdout(f):
            user_code.print_welcome_messages(students)
        output = normalize_text(f.getvalue())
        for name in students:
            expected = normalize_text(f"Welcome to class, {name}!")
            _dynamic_test(
                self,
                expected in output,
                f"Message for {name} is printed correctly.",
                f"Expected welcome message for '{name}' not found in output: {output}",
            )

    def test_correct_format(self):
        import user_code
        importlib.reload(user_code)
        students = ["Sam"]
        f = io.StringIO()
        with redirect_stdout(f):
            user_code.print_welcome_messages(students)
        output = normalize_text(f.getvalue())
        expected = normalize_text("Welcome to class, Sam!")
        _dynamic_test(
            self,
            expected in output,
            "Message format is correct for single student.",
            f"Expected message format: '{expected}', got: '{output}'",
        )

    def test_empty_list(self):
        import user_code
        importlib.reload(user_code)
        students = []
        f = io.StringIO()
        with redirect_stdout(f):
            user_code.print_welcome_messages(students)
        output = normalize_text(f.getvalue())
        _dynamic_test(
            self,
            output.strip() == "",
            "No output for empty student list.",
            f"Expected no output, got: '{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

A beginner-friendly Python course designed specifically for teachers. Learn how to use Python to organize grades, analyze student performance, and automate classroom tasks with engaging, real-world examples.

Learn the basics of Python programming with a focus on classroom and grade organization. This section introduces Python syntax, variables, and simple data structures through relatable educational scenarios.

Dive deeper into Python by learning how to organize, analyze, and visualize student grades. This section covers dictionaries, conditional logic, and basic data analysis techniques tailored for teachers.

Explore how Python can automate common classroom tasks such as attendance tracking, assignment management, and generating reports. This section introduces file operations and more advanced automation techniques.

Challenge: Generate Welcome Messages

解答