How to downcase the first character of a string?

Question

There is a function to capitalize a string, I would like to be able to change the first character of a string to be sure it will be lowercase.

How can I do that in Python?

Asked By: Natim

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Source

Answer 1

def first_lower(s):
   if len(s) == 0:
      return s
   else:
      return s[0].lower() + s[1:]

print first_lower("HELLO")  # Prints "hELLO"
print first_lower("")       # Doesn't crash  :-)

Answered By: RichieHindle

Answer 2

Simplest way:

>>> mystring = 'ABCDE'
>>> mystring[0].lower() + mystring[1:]
'aBCDE'
>>>

Update

See this answer (by @RichieHindle) for a more foolproof solution, including handling empty strings. That answer doesn’t handle None though, so here is my take:

>>> def first_lower(s):
   if not s: # Added to handle case where s == None
   return 
   else:
      return s[0].lower() + s[1:]

>>> first_lower(None)
>>> first_lower("HELLO")
'hELLO'
>>> first_lower("")
>>>

Answered By: Manoj Govindan

Answer 3

s = "Bobby tables"
s = s[0].lower() + s[1:]

Answered By: JoshD

Answer 4

Interestingly, none of these answers does exactly the opposite of capitalize(). For example, capitalize('abC') returns Abc rather than AbC. If you want the opposite of capitalize(), you need something like:

def uncapitalize(s):
  if len(s) > 0:
    s = s[0].lower() + s[1:].upper()
  return s

Answered By: Adrian McCarthy

Answer 5

I’d write it this way:

def first_lower(s):
    if s == "":
        return s
    return s[0].lower() + s[1:]

This has the (relative) merit that it will throw an error if you inadvertently pass it something that isn’t a string, like None or an empty list.

Answered By: Robert Rossney

Answer 6

No need to handle special cases (and I think the symmetry is more Pythonic):

def uncapitalize(s):
    return s[:1].lower() + s[1:].upper()

Answered By: Don O'Donnell

Answer 7

One-liner which handles empty strings and None:

func = lambda s: s[:1].lower() + s[1:] if s else ''

>>> func(None)
>>> ''
>>> func('')
>>> ''
>>> func('MARTINEAU')
>>> 'mARTINEAU'

Answered By: martineau

Answer 8

This duplicate post lead me here.

If you’ve a list of strings like the one shown below

l = ['SentMessage', 'DeliverySucceeded', 'DeliveryFailed']

Then, to convert the first letter of all items in the list, you can use

l = [x[0].lower() + x[1:] for x in l]

Output

['sentMessage', 'deliverySucceeded', 'deliveryFailed']

Answered By: Van Peer

Answer 9

pip install pydash first.

import pydash  # pip install pydash

assert pydash.lower_first("WriteLine") == "writeLine"

https://github.com/dgilland/pydash

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

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

Answered By: BaiJiFeiLong

How to downcase the first character of a string?

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