⚡️ Speed up to_snake() by 27% in pydantic/alias_generators.py (#9747)

Co-authored-by: codeflash-ai[bot] <148906541+codeflash-ai[bot]@users.noreply.github.com>
Co-authored-by: Sydney Runkle <[email protected]>

Author: 3 people

pydantic/alias_generators.py

@@ -49,9 +49,13 @@ def to_snake(camel: str) -> str:
     Returns:
         The converted string in snake_case.
     """
-    snake = re.sub(r'([a-zA-Z])([0-9])', lambda m: f'{m.group(1)}_{m.group(2)}', camel)
-    snake = re.sub(r'([a-z0-9])([A-Z])', lambda m: f'{m.group(1)}_{m.group(2)}', snake)
-    snake = re.sub(r'([A-Z]+)([A-Z][a-z])', lambda m: f'{m.group(1)}_{m.group(2)}', snake)
-    # Replace hyphens with underscores to handle kebab-case
-    snake = snake.replace('-', '_')
+    # `(?<=[a-zA-Z])(?=[0-9])` matches the space between a letter and a digit
+    # `(?<=[a-z0-9])(?=[A-Z])` matches the space between a lowercase letter / digit and uppercase letter
+    # `(?<=[A-Z])(?=[A-Z][a-z])` matches the space between two uppercase letters when the latter is followed by a lowercase letter
+    # `-` matches a hyphen in order to convert kebab case strings
+    snake = re.sub(
+        r'(?<=[a-zA-Z])(?=[0-9])|(?<=[a-z0-9])(?=[A-Z])|(?<=[A-Z])(?=[A-Z][a-z])|-',
+        '_',
+        camel,
+    )
     return snake.lower()