Decapitalizes the first letter of a string.

Decapitalize the first letter of the string and then add it with rest of the string.
Omit the upper_rest parameter to keep the rest of the string intact, or set it to True to convert to uppercase.


def decapitalize(s, upper_rest=False):
  return s[:1].lower() + (s[1:].upper() if upper_rest else s[1:])


decapitalize('FooBar') # 'fooBar'
decapitalize('FooBar', True) # 'fOOBAR'