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Changing one character in a string


Question

What is the easiest way in Python to replace a character in a string?

For example:

text = "abcdefg";
text[1] = "Z";
           ^
2020/06/17
1
396
6/17/2020 11:35:02 PM

Accepted Answer

Don't modify strings.

Work with them as lists; turn them into strings only when needed.

>>> s = list("Hello zorld")
>>> s
['H', 'e', 'l', 'l', 'o', ' ', 'z', 'o', 'r', 'l', 'd']
>>> s[6] = 'W'
>>> s
['H', 'e', 'l', 'l', 'o', ' ', 'W', 'o', 'r', 'l', 'd']
>>> "".join(s)
'Hello World'

Python strings are immutable (i.e. they can't be modified). There are a lot of reasons for this. Use lists until you have no choice, only then turn them into strings.

2009/08/04
555
8/4/2009 4:41:07 PM


new = text[:1] + 'Z' + text[2:]
2009/08/16

Python strings are immutable, you change them by making a copy.
The easiest way to do what you want is probably:

text = "Z" + text[1:]

The text[1:] returns the string in text from position 1 to the end, positions count from 0 so '1' is the second character.

edit: You can use the same string slicing technique for any part of the string

text = text[:1] + "Z" + text[2:]

Or if the letter only appears once you can use the search and replace technique suggested below

2020/05/28

Starting with python 2.6 and python 3 you can use bytearrays which are mutable (can be changed element-wise unlike strings):

s = "abcdefg"
b_s = bytearray(s)
b_s[1] = "Z"
s = str(b_s)
print s
aZcdefg

edit: Changed str to s

edit2: As Two-Bit Alchemist mentioned in the comments, this code does not work with unicode.

2015/11/30

Like other people have said, generally Python strings are supposed to be immutable.

However, if you are using CPython, the implementation at python.org, it is possible to use ctypes to modify the string structure in memory.

Here is an example where I use the technique to clear a string.

Mark data as sensitive in python

I mention this for the sake of completeness, and this should be your last resort as it is hackish.

2017/05/23

This code is not mine. I couldn't recall the site form where, I took it. Interestingly, you can use this to replace one character or more with one or more charectors. Though this reply is very late, novices like me (anytime) might find it useful.

Change Text function.

mytext = 'Hello Zorld'
mytext = mytext.replace('Z', 'W')
print mytext,
2020/06/20

Source: https://stackoverflow.com/questions/1228299
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