'in-place' string modifications in Python

Question

In Python, strings are immutable.

What is the standard idiom to walk through a string character-by-character and modify it?

The only methods I can think of are some genuinely stanky hacks related to joining against a result string.

--

In C:

for(int i = 0; i < strlen(s); i++)
{
   s[i] = F(s[i]);
}

This is super expressive and says exactly what I am doing. That is what I am looking for.

Answer 1

Don't use a string, use something mutable like bytearray:

#!/usr/bin/python

s = bytearray("my dog has fleas")
for n in xrange(len(s)):
    s[n] = chr(s[n]).upper()
print s

Results in:

MY DOG HAS FLEAS

Edit:

Since this is a bytearray, you aren't (necessarily) working with characters. You're working with bytes. So this works too:

s = bytearray("x81x82x83")
for n in xrange(len(s)):
    s[n] = s[n] + 1
print repr(s)

gives:

bytearray(b'x82x83x84')

If you want to modify characters in a Unicode string, you'd maybe want to work with memoryview, though that doesn't support Unicode directly.