CODEWITHSUNDEEP
pythonpython-2.7camelcasingsnakecasing
luca
luca

Reputation: 12601

Converting Snake Case to Lower Camel Case (lowerCamelCase)

What would be a good way to convert from snake case (my_string) to lower camel case (myString) in Python 2.7?

The obvious solution is to split by underscore, capitalize each word except the first one and join back together.

However, I'm curious as to other, more idiomatic solutions or a way to use RegExp to achieve this (with some case modifier?)

Upvotes: 123

Views: 94847

Answers (16)

Antoine Pinsard
Antoine Pinsard

Reputation: 34972

Here is a solution using regular expressions:

import re

def snake_to_camel(text):
    return re.sub('_([a-zA-Z0-9])', lambda m: m[1].upper(), text)

Upvotes: 3

jbaiter
jbaiter

Reputation: 7099

def to_camel_case(snake_str):
    return "".join(x.capitalize() for x in snake_str.lower().split("_"))

def to_lower_camel_case(snake_str):
    # We capitalize the first letter of each component except the first one
    # with the 'capitalize' method and join them together.
    camel_string = to_camel_case(snake_str)
    return snake_str[0].lower() + camel_string[1:]

Example:

In [11]: to_lower_camel_case('snake_case')
Out[11]: 'snakeCase'

In [12]: to_lower_camel_case('SNAKE_Case')
Out[12]: 'snakeCase'

In [13]: to_lower_camel_case('SNAKE_CASE')
Out[13]: 'snakeCase'

Upvotes: 221

Hemingway_PL
Hemingway_PL

Reputation: 21

I personally use this solution since it is a rolling transformation:

from functools import reduce

def camelize(snake_string: str) -> str:
    return reduce(lambda x, y: x + y.capitalize(), snake_string.split('_'))

Upvotes: 2

Steve Wells
Steve Wells

Reputation: 164

it this too simple?

snake_case is already lowercase. my_string

So if we title the string and remove the underscores MyString

then replace the first character M with the original m we're done.

scase = "my_string"
ccase = scase[0] + scase.title().replace('_', '')[1:]

output: myString

Upvotes: 5

BaiJiFeiLong
BaiJiFeiLong

Reputation: 4635

You can use pydash if you are familiar with lodash.

pip install pydash first.

import pydash  # pip install pydash

assert pydash.snake_case("WriteLine") == "write_line"
assert pydash.snake_case("writeLine") == "write_line"
assert pydash.camel_case("write_line") == "writeLine"
assert pydash.upper_first(pydash.camel_case("write_line")) == "WriteLine"

https://github.com/dgilland/pydash

https://pydash.readthedocs.io/en/latest/

https://pypi.org/project/pydash/

Upvotes: 1

Tearf001
Tearf001

Reputation: 131

for one-line fans..

''.join((wd.title() if i else wd) for (i,wd) in enumerate(string.split('_')))

Upvotes: 4

Blessed Geek
Blessed Geek

Reputation: 21664

def toCamel(snake)
    return ''.join( word.capitalize()
                    for word in snake.split('_') )

Allow underscore to be escaped by a preceding underscore (e.g. 'Escaped__snake' would become 'Escaped_Snake', while 'usual_snake' becomes 'UsualSnake'. Include ternary test for blank.

def toCamel(escaped_snake)
    return ''.join( (word.capitalize(), '_')[word=='')
                    for word in escaped_snake.split('_') )

Don't capitalize the 1st segment (i.e, 'tHERE_is_a_snake' becomes 'thereIsASnake')

def toCamel(esCAPed_snake)
    words = esCAPed_snake.split('_')
    return words[0].lower() + ''.join( (word.capitalize(), '_')[word=='')
                                       for word in words[1:] )

Upvotes: 2

Berislav Lopac
Berislav Lopac

Reputation: 17243

Here's yet another take, which works only in Python 3.5 and higher:

def camel(snake_str):
    first, *others = snake_str.split('_')
    return ''.join([first.lower(), *map(str.title, others)])

Upvotes: 31

Mike Starov
Mike Starov

Reputation: 7296

So I needed to convert a whole file with bunch of snake case parameters into camel case. The solution by Mathieu Rodic worked best. Thanks.

Here is a little script to use it on files.

import re

f = open("in.txt", "r")
words = f.read()

def to_camel_case3(s):
    return re.sub(r'_([a-z])', lambda x: x.group(1).upper(), s)

f = open("out.txt", "w")
f.write(to_camel_case3(words))

Upvotes: 0

Glenn Dills
Glenn Dills

Reputation: 281

A little late to this, but I found this on /r/python a couple days ago:

pip install pyhumps

and then you can just do:

import humps

humps.camelize('jack_in_the_box')  # jackInTheBox
# or
humps.decamelize('rubyTuesdays')  # ruby_tuesdays
# or
humps.pascalize('red_robin')  # RedRobin

Upvotes: 28

Syas
Syas

Reputation: 115

Without using list comprehensions:

def snake_to_camel_case(text_snake):
    return '{}{}'.format(
        text_snake[:1].lower(),
        text_snake.title().replace('_', '')[1:],
    )

Upvotes: 0

Chandler Childs
Chandler Childs

Reputation: 1

def to_camel_case(snake_str):
    components = snake_str.split('_')
    return reduce(lambda x, y: x + y.title(), components[1:], components[0])

Upvotes: 0

MLev
MLev

Reputation: 435

Building on Steve's answer, this version should work:

def to_camel_case(snake_case_string):
    titleCaseVersion =  snake_case_string.title().replace("_", "")
    camelCaseVersion = titleCaseVersion[0].lower() + titleCaseVersion[1:]
    return camelCaseVersion

Upvotes: 3

steve
steve

Reputation: 163

another one liner

def to_camel_case(snake_string):
    return snake_string.title().replace("_", "")

Upvotes: 12

Simeon Visser
Simeon Visser

Reputation: 122376

Obligatory one-liner:

import string

def to_camel_case(s):
    return s[0].lower() + string.capwords(s, sep='_').replace('_', '')[1:] if s else s

Upvotes: 9

Leon Young
Leon Young

Reputation: 585

>>> snake_case = "this_is_a_snake_case_string"
>>> l = snake_case.split("_")
>>> print l[0] + "".join(map(str.capitalize, l[1:]))
'thisIsASnakeCaseString'

Upvotes: 5

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