Case conversion Python functions

Capitalize string

In order to capitalize the first letter of a string, you can use list slicing and the str.upper() method. Then, use str.join() to combine the capitalized first letter with the rest of the characters. Omit the lower_rest parameter to keep the rest of the string intact, or set it to True to convert to lowercase.

def capitalize(s, lower_rest = False):
  return ''.join([s[:1].upper(), (s[1:].lower() if lower_rest else s[1:])])

capitalize('fooBar') # 'FooBar'
capitalize('fooBar', True) # 'Foobar'

Decapitalize string

To decapitalize the first letter of a string, you can use the exact same method as above, but with the str.lower() method instead of str.upper().

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

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

Capitalize every word

To capitalize every word in a string, you can use the str.title() method.

def capitalize_every_word(s):
  return s.title()

capitalize_every_word('hello world!') # 'Hello World!'

Camel case string

To convert a string to camel case, you can use re.sub() to replace any - or _ with a space, using the regexp r"(_|-)+". Then, use str.title() to capitalize every word and convert the rest to lowercase. Finally, use str.replace() to remove any spaces between words.

from re import sub

def camel(s):
  s = sub(r"(_|-)+", " ", s).title().replace(" ", "")
  return ''.join([s[0].lower(), s[1:]])

camel('some_database_field_name') # 'someDatabaseFieldName'
camel('Some label that needs to be camelized')
# 'someLabelThatNeedsToBeCamelized'
camel('some-javascript-property') # 'someJavascriptProperty'
camel('some-mixed_string with spaces_underscores-and-hyphens')
# 'someMixedStringWithSpacesUnderscoresAndHyphens'

Kebab case string

To kebab case a string, you'll use the same method as above, except replace str.title() with re.sub() to match all words in the string and then use str.lower() to convert them to lowercase. Finally, use str.replace() to replace spaces with -.

from re import sub

def kebab(s):
  return '-'.join(
    sub(r"(\s|_|-)+"," ",
    sub(r"[A-Z]{2,}(?=[A-Z][a-z]+[0-9]*|\b)|[A-Z]?[a-z]+[0-9]*|[A-Z]|[0-9]+",
    lambda mo: ' ' + mo.group(0).lower(), s)).split())

kebab('camelCase') # 'camel-case'
kebab('some text') # 'some-text'
kebab('some-mixed_string With spaces_underscores-and-hyphens')
# 'some-mixed-string-with-spaces-underscores-and-hyphens'
kebab('AllThe-small Things') # 'all-the-small-things'

Snake case string

To snake case a string, you can use the same method as above, but replace the - with _.

from re import sub

def snake(s):
  return '_'.join(
    sub('([A-Z][a-z]+)', r' \1',
    sub('([A-Z]+)', r' \1',
    s.replace('-', ' '))).split()).lower()

snake('camelCase') # 'camel_case'
snake('some text') # 'some_text'
snake('some-mixed_string With spaces_underscores-and-hyphens')
# 'some_mixed_string_with_spaces_underscores_and_hyphens'
snake('AllThe-small Things') # 'all_the_small_things'