Implement Recursive Array Flattening Function with Comprehensive Testing

src/array_flatten.py

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+from typing import List, Union, Any
+
+def flatten_array(arr: List[Any]) -> List[Any]:
+    """
+    Recursively flatten a nested array of arbitrary depth into a single-level array.
+
+    Args:
+        arr (List[Any]): A nested list that may contain other lists or nested lists.
+
+    Returns:
+        List[Any]: A flattened list with all nested elements at the top level.
+
+    Examples:
+        >>> flatten_array([1, [2, 3], [4, [5, 6]]])
+        [1, 2, 3, 4, 5, 6]
+        >>> flatten_array([])
+        []
+        >>> flatten_array([1, 2, 3])
+        [1, 2, 3]
+    """
+    flattened = []
+
+    for item in arr:
+        # If the item is a list, recursively flatten it
+        if isinstance(item, list):
+            flattened.extend(flatten_array(item))
+        else:
+            # If not a list, add the item directly
+            flattened.append(item)
+
+    return flattened

tests/test_array_flatten.py

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+import pytest
+from src.array_flatten import flatten_array
+
+def test_flatten_empty_array():
+    """Test flattening an empty array."""
+    assert flatten_array([]) == []
+
+def test_flatten_single_level_array():
+    """Test flattening an already flat array."""
+    assert flatten_array([1, 2, 3]) == [1, 2, 3]
+
+def test_flatten_simple_nested_array():
+    """Test flattening a simply nested array."""
+    assert flatten_array([1, [2, 3], 4]) == [1, 2, 3, 4]
+
+def test_flatten_deeply_nested_array():
+    """Test flattening a deeply nested array."""
+    assert flatten_array([1, [2, [3, 4]], [5, 6]]) == [1, 2, 3, 4, 5, 6]
+
+def test_flatten_mixed_nested_array():
+    """Test flattening an array with various nesting levels."""
+    assert flatten_array([1, [2, 3, [4, 5]], 6, [7, [8, 9]]]) == [1, 2, 3, 4, 5, 6, 7, 8, 9]
+
+def test_flatten_array_with_different_types():
+    """Test flattening an array with different types of elements."""
+    assert flatten_array([1, ['a', 'b'], [2, ['c']]]) == [1, 'a', 'b', 2, 'c']