python function capitalize first letter only

Question

I need build a function to transform 1st character only, from any word but also this function need address the problem if the 1st character from the word doesn't starts with a character, for example '_sun',' -tree', '2cat' these words need be like _Sun, -Tree, 2Cat. This is what I have so far, it can convert any word but I don't know how do 2nd part, need use ASCII?? to get value of 1st character and see if the word starts with character?

def convert(capital):
    return capital[0].upper() + capital[1:]

def main():
   print(convert('sun'))

main()

Martijn Pieters · Accepted Answer · 2015-02-02T15:37:07.847

Your function capitalises the first character, regardless.

For this task, you'll have to find the first character in a different way; you could use str.isalpha() function:

def convert(capital):
    index = 0
    while index < len(capital) and not capital[index].isalpha():
        index += 1
    return capital[:index] + capital[index:].capitalize()

Another approach would be to use a regular expression-based substitution; you'll have to use a function to uppercase the character found:

import re

def convert(capital):
    return re.sub(r'([a-z])(.*)$', lambda m: m.group(1).upper() + m.group(2),
                  capital, flags=re.I)

This matches case-insensitively on the first letter, and replaces that with the uppercase version.

A third idea is to use str.title(), which does the same for all words in a text, but only apply it to the first word:

def convert(capital):
    first, _, rest = capital.partition(' ')
    return '{} {}'.format(first.title(), rest)

It's too bad `str.title` doesn't accept an agument for "number of words to capitalize". That'd be perfect here :-) — mgilson, Feb 02 '15 at 15:35
@mgilson: you can still use it, but you'd have to split on the first space. Added that in. — Martijn Pieters, Feb 02 '15 at 15:37

score 2 · Answer 2 · answered Feb 02 '15 at 15:29

2

One option is to use a regex and limit it to 1 replacement, eg:

>>> import re
>>> re.sub('[a-zA-Z]', lambda m: m.group().upper(), '2cat', 1)
'2Cat'
>>> re.sub('[a-zA-Z]', lambda m: m.group().upper(), 'sun', 1)
'Sun'

answered Feb 02 '15 at 15:29

Jon Clements

138,671
33
247
280

score 0 · Answer 3 · answered Feb 02 '15 at 15:38

0

You only seem to have either a word starting with a letter or where the second character is a letter so you just have two possibilities:

print(s.capitalize() if s[0].isalpha() else s[0] +  s[1:].capitalize())

answered Feb 02 '15 at 15:38

Padraic Cunningham

176,452
29
245
321

This is rather limited though; I'm sure the OP will come back and ask about *but what about `'_-sun'`*? – Martijn Pieters Feb 02 '15 at 15:42
@MartijnPieters, *I need build a function to transform 1st character only from any word but also this function need address the problem if the 1st character from the word doesn't starts with a character* , that is what the code does. – Padraic Cunningham Feb 02 '15 at 15:43
Sure, it solves that problem. But it seldom ever is that simple. – Martijn Pieters Feb 02 '15 at 15:45
@MartijnPieters, well i will leave that to the OP to decide. – Padraic Cunningham Feb 02 '15 at 15:48

python function capitalize first letter only

3 Answers3