[Tutor] How to change the char in string for Python

[Steven D'Aprano]

On 24/02/13 21:56, Sudo Nohup wrote:
> Dear all,
>
> I want to change the value of a char in a string for Python. However, It
> seems that "=" does not work.


Strings are immutable, which means that you cannot modify them in place. You can only create a new string with the characters you want.

If you want to change one letter, the simplest way is with string slicing:

s = "Hello world!"
t = s[:6] + "W" + s[7:]
print t
=> prints "Hello World!"


If you want to change many letters, the best way is to create a new list of the characters, and then join them:

s = "Hello"
chars = [chr(ord(c) + 13) for c in s]
t = ''.join(chars)
print t
=> prints 'Uryy|'



Best still is to use the string methods, if you can, such as str.upper(), str.replace(), etc.

http://docs.python.org/2/tutorial/introduction.html#strings

http://docs.python.org/2/library/stdtypes.html#string-methods



-- 
Steven