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";            ^ 

Answer 1

Fastest method?

There are three ways. For the speed seekers I recommend 'Method 2'

Method 1

Given by this answer

text = 'abcdefg' new = list(text) new[6] = 'W' ''.join(new) 

Which is pretty slow compared to 'Method 2'

timeit.timeit("text = 'abcdefg'; s = list(text); s[6] = 'W'; ''.join(s)", number=1000000) 1.0411581993103027 

Method 2 (FAST METHOD)

Given by this answer

text = 'abcdefg' text = text[:1] + 'Z' + text[2:] 

Which is much faster:

timeit.timeit("text = 'abcdefg'; text = text[:1] + 'Z' + text[2:]", number=1000000) 0.34651994705200195 

Method 3:

Byte array:

timeit.timeit("text = 'abcdefg'; s = bytearray(text); s[1] = 'Z'; str(s)", number=1000000) 1.0387420654296875 

Answer 2

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.