camelCase to snake_case conversion - Fixes #9726

strings/camel_case_to_snake_case.py

@@ -0,0 +1,55 @@
+def camel_to_snake_case(input_str: str) -> str:
+    """
+    Transforms a camelCase (or PascalCase) string to snake_case
+
+    >>> camel_to_snake_case("someRandomString")
+    'some_random_string'
+
+    >>> camel_to_snake_case("SomeRandomString")
+    'some_random_string'
+
+    >>> camel_to_snake_case("123someRandom123String123")
+    '123_some_random_123_string_123'
+
+    >>> camel_to_snake_case("123SomeRandom123String123")
+    '123_some_random_123_string_123'
+
+    >>> camel_to_snake_case(123)
+    Traceback (most recent call last):
+        ...
+    ValueError: Expected string as input, found <class 'int'>
+
+    """
+
+    import re
+
+    # check for invalid input type
+    if not isinstance(input_str, str):
+        msg = f"Expected string as input, found {type(input_str)}"
+        raise ValueError(msg)
+
+    # Replace all characters that are not letters or numbers with the underscore
+    snake_str = re.sub(r"[^a-zA-Z0-9]", "_", input_str)
+
+    # Find where lowercase meets uppercase. Insert underscore between them
+    snake_str = re.sub(r"([a-z])([A-Z])", r"\1_\2", snake_str).lower()
+
+    # Find the sequence of digits at the beginning
+    snake_str = re.sub(r"^(\d+)", r"\1_", snake_str)
+
+    # Find the sequence of digits at the end
+    snake_str = re.sub(r"(\d+)$", r"_\1", snake_str)
+
+    # Find where letter meets digits
+    snake_str = re.sub(r"([a-z])(\d+)", r"\1_\2", snake_str)
+
+    # Find where digits meet letter
+    snake_str = re.sub(r"(\d+)([a-z])", r"\1_\2", snake_str)
+
+    return snake_str
+
+
+if __name__ == "__main__":
+    from doctest import testmod
+
+    testmod()