‘in-place’ string modifications in Python

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("\x81\x82\x83")
for n in xrange(len(s)):
    s[n] = s[n] + 1
print repr(s)

gives:

bytearray(b'\x82\x83\x84')

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.