Robust String Reversal Implementation with Comprehensive Input Handling

src/string_reversal.py

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+def reverse_string(s: str) -> str:
+    """
+    Reverses the input string using a manual character-by-character approach.
+
+    Args:
+        s (str): The input string to be reversed.
+
+    Returns:
+        str: The reversed string.
+
+    Raises:
+        TypeError: If the input is not a string.
+    """
+    # Check if input is a string
+    if not isinstance(s, str):
+        raise TypeError("Input must be a string")
+
+    # Convert string to list of characters and reverse manually
+    chars = list(s)
+    left, right = 0, len(chars) - 1
+
+    while left < right:
+        # Swap characters from both ends
+        chars[left], chars[right] = chars[right], chars[left]
+        left += 1
+        right -= 1
+
+    # Convert back to string and return
+    return ''.join(chars)

tests/test_string_reversal.py

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+import pytest
+from src.string_reversal import reverse_string
+
+def test_reverse_string_basic():
+    """Test basic string reversal."""
+    assert reverse_string("hello") == "olleh"
+    assert reverse_string("python") == "nohtyp"
+
+def test_reverse_string_empty():
+    """Test reversal of an empty string."""
+    assert reverse_string("") == ""
+
+def test_reverse_string_single_char():
+    """Test reversal of a single character."""
+    assert reverse_string("a") == "a"
+
+def test_reverse_string_with_spaces():
+    """Test reversal of string with spaces."""
+    assert reverse_string("hello world") == "dlrow olleh"
+
+def test_reverse_string_with_special_chars():
+    """Test reversal of string with special characters."""
+    assert reverse_string("a1b2c3") == "3c2b1a"
+
+def test_reverse_string_invalid_input():
+    """Test that TypeError is raised for non-string inputs."""
+    with pytest.raises(TypeError, match="Input must be a string"):
+        reverse_string(123)
+
+    with pytest.raises(TypeError, match="Input must be a string"):
+        reverse_string(None)
+
+    with pytest.raises(TypeError, match="Input must be a string"):
+        reverse_string(["hello"])