Convert camel-case to snake-case in python. e.g.: CamelCase -> snake_case e.g.: snake_case -> CamelCase e.g.: CamelCase -> dash-case e.g.: dash-case -> CamelCase By: Jay Taylor [@jtaylor] Me<modifier>: Yahya Kacem <[email protected]> Original gist: https://gist.github.com/jaytaylor/3660565

string_converter.py

#!/usr/bin/env python
"""
  Convert camel-case to snake-case in python.
  e.g.: CamelCase  -> snake_case
  e.g.: snake_case -> CamelCase
  e.g.: CamelCase  -> dash-case
  e.g.: dash-case  -> CamelCase
  By:            Jay Taylor [@jtaylor]
  Me<modifier>:  Yahya Kacem <[email protected]>
  Original gist: https://gist.github.com/jaytaylor/3660565
"""
import re

class Converter:
  
  def __init__(self):
    self._first_cap_re = re.compile(r'(.)([A-Z][a-z]+)')
    self._all_cap_re   = re.compile('([a-z0-9])([A-Z])')

  def camel_to_snake(self, camelCasedStr):
    """ 
    This function converts to snake_case from camelCase
    """
    sub1            = self._first_cap_re.sub(r'\1_\2', camelCasedStr)
    snake_cased_str = self._all_cap_re.sub(r'\1_\2', sub1).lower()
    return snake_cased_str.replace('__', '_')

  def camelToDash(self, camelCasedStr):
    """ 
    This function converts to dashed_case from camelCase
    """
    sub2            = self._first_cap_re.sub(r'\1-\2', camelCasedStr)
    dashed_case_str = self._all_cap_re.sub(r'\1-\2', sub2).lower()
    return dashed_case_str.replace('--', '-')

  def snakeToCamel(self, snake_cased_str):
    return self._convertToCamel(snake_cased_str, "_")

  def dashToCamel(self, snake_cased_str):
    return self._convertToCamel(snake_cased_str, "-")

  def _convertToCamel(self, snake_cased_str, separator):
    components = snake_cased_str.split(separator)
    preffix    = ""
    suffix     = ""
    if components[0] == "":
      components = components[1:]
      preffix    = separator
    if components[-1] == "":
      components = components[:-1]
      suffix     = separator
    if len(components) > 1:
      camelCasedStr = components[0].lower()
      for x in components[1:]:
        if x.isupper() or x.istitle():
          camelCasedStr += x
        else:
          camelCasedStr += x.title()
    else:
      camelCasedStr = components[0]
    return preffix + camelCasedStr + suffix

test_string_converter.py

#!/usr/bin/env python
"""
  Convert camel-case to snake-case in python.
  e.g.: CamelCase  -> snake_case
  e.g.: snake_case -> CamelCase
  e.g.: CamelCase  -> dash-case
  e.g.: dash-case  -> CamelCase
  By:            Jay Taylor [@jtaylor]
  Me<modifier>:  Yahya Kacem <[email protected]>
  Original gist: https://gist.github.com/jaytaylor/3660565
"""
import Converter as C

Converter = C.Converter()

def test_camel_to_snake():
  assert Converter.camel_to_snake('snakesOnAPlane') == 'snakes_on_a_plane'
  assert Converter.camel_to_snake('SnakesOnAPlane') == 'snakes_on_a_plane'
  assert Converter.camel_to_snake('_Snakes_On_APlane_') == '_snakes_on_a_plane_'
  assert Converter.camel_to_snake('snakes_on_a_plane') == 'snakes_on_a_plane'
  assert Converter.camel_to_snake('IPhoneHysteria') == 'i_phone_hysteria'
  assert Converter.camel_to_snake('iPhoneHysteria') == 'i_phone_hysteria'
  assert Converter.camel_to_snake('iPHONEHysteria') == 'i_phone_hysteria'
  assert Converter.camel_to_snake('_iPHONEHysteria') == '_i_phone_hysteria'
  assert Converter.camel_to_snake('iPHONEHysteria_') == 'i_phone_hysteria_'
  print "all camelCase to snake_case tests passed"

def testCamelToDash():
  assert Converter.camelToDash('snakesOnAPlane') == 'snakes-on-a-plane'
  assert Converter.camelToDash('SnakesOnAPlane') == 'snakes-on-a-plane'
  assert Converter.camelToDash('-Snakes-On-APlane-') == '-snakes-on-a-plane-'
  assert Converter.camelToDash('snakes-on-a-plane') == 'snakes-on-a-plane'
  assert Converter.camelToDash('IPhoneHysteria') == 'i-phone-hysteria'
  assert Converter.camelToDash('iPhoneHysteria') == 'i-phone-hysteria'
  assert Converter.camelToDash('iPHONEHysteria') == 'i-phone-hysteria'
  assert Converter.camelToDash('-iPHONEHysteria') == '-i-phone-hysteria'
  assert Converter.camelToDash('iPHONEHysteria-') == 'i-phone-hysteria-'
  print "all camelCase to dash-case tests passed"

def testSnakeToCamel():
  assert Converter.snakeToCamel('_snakes_on_a_plane_') == '_snakesOnAPlane_'
  assert Converter.snakeToCamel('snakes_on_a_plane') == 'snakesOnAPlane'
  assert Converter.snakeToCamel('Snakes_on_a_plane') == 'snakesOnAPlane'
  assert Converter.snakeToCamel('snakesOnAPlane') == 'snakesOnAPlane'
  assert Converter.snakeToCamel('I_phone_hysteria') == 'iPhoneHysteria'
  assert Converter.snakeToCamel('i_phone_hysteria') == 'iPhoneHysteria'
  assert Converter.snakeToCamel('i_PHONE_hysteria') == 'iPHONEHysteria'
  assert Converter.snakeToCamel('_i_phone_hysteria') == '_iPhoneHysteria'
  assert Converter.snakeToCamel('i_phone_hysteria_') == 'iPhoneHysteria_'
  print "all snake_case to camelCase tests passed"

def testDashToCamel():
  assert Converter.dashToCamel('-snakes-on-a-plane-') == '-snakesOnAPlane-'
  assert Converter.dashToCamel('snakes-on-a-plane') == 'snakesOnAPlane'
  assert Converter.dashToCamel('Snakes-on-a-plane') == 'snakesOnAPlane'
  assert Converter.dashToCamel('snakesOnAPlane') == 'snakesOnAPlane'
  assert Converter.dashToCamel('I-phone-hysteria') == 'iPhoneHysteria'
  assert Converter.dashToCamel('i-phone-hysteria') == 'iPhoneHysteria'
  assert Converter.dashToCamel('i-PHONE-hysteria') == 'iPHONEHysteria'
  assert Converter.dashToCamel('-i-phone-hysteria') == '-iPhoneHysteria'
  assert Converter.dashToCamel('i-phone-hysteria-') == 'iPhoneHysteria-'
  print "all dash-case to camelCase tests passed"

def run_tests():
  test_camel_to_snake()
  print "################################################################"
  testCamelToDash()
  print "################################################################"
  testSnakeToCamel()
  print "################################################################"
  testDashToCamel()
  print "################################################################"

if __name__ == '__main__':
  print "################################################################"
  print "################################################################"
  run_tests()
  print 'All tests passed.'
  print "################################################################"
  print "################################################################"

+1 on @mbylstra suggestion, I realise we don't have to turn Python into JS where each single-liner becomes its own dependency but some things just deserve to be

The Inflection library handle this case and is already in PIP.