python capitalize first letter only

Only because no one else has mentioned it:

>>> 'bob'.title()
'Bob'
>>> 'sandy'.title()
'Sandy'
>>> '1bob'.title()
'1Bob'
>>> '1sandy'.title()
'1Sandy'

However, this would also give

>>> '1bob sandy'.title()
'1Bob Sandy'
>>> '1JoeBob'.title()
'1Joebob'

i.e. it doesn't just capitalize the first alphabetic character. But then .capitalize() has the same issue, at least in that 'joe Bob'.capitalize() == 'Joe bob', so meh.

If the first character is an integer, it will not capitalize the first letter.

>>> '2s'.capitalize()
'2s'

If you want the functionality, strip off the digits, you can use '2'.isdigit() to check for each character.

>>> s = '123sa'
>>> for i, c in enumerate(s):
...     if not c.isdigit():
...         break
... 
>>> s[:i] + s[i:].capitalize()
'123Sa'

This is similar to @Anon's answer in that it keeps the rest of the string's case intact, without the need for the re module.

def sliceindex(x):
    i = 0
    for c in x:
        if c.isalpha():
            i = i + 1
            return i
        i = i + 1

def upperfirst(x):
    i = sliceindex(x)
    return x[:i].upper() + x[i:]

x = '0thisIsCamelCase'

y = upperfirst(x)

print(y)
# 0ThisIsCamelCase

As @Xan pointed out, the function could use more error checking (such as checking that x is a sequence - however I'm omitting edge cases to illustrate the technique)

Updated per @normanius comment (thanks!)

Thanks to @GeoStoneMarten in pointing out I didn't answer the question! -fixed that

Here is a one-liner that will uppercase the first letter and leave the case of all subsequent letters:

import re

key = 'wordsWithOtherUppercaseLetters'
key = re.sub('([a-zA-Z])', lambda x: x.groups()[0].upper(), key, 1)
print key

This will result in WordsWithOtherUppercaseLetters