Are there differences between string.replace / .strip / .find and the built-in functions?

I have a Python 2 codebase which I'm migrating to Python 3. The old codebase uses

import string

foo = string.replace(s, old, new)
foo = string.strip(s)
foo = string.find(s, sub, start, end)

I moved it with 2to3, but this gives an error. My guess is that I have to replace the above by

foo = s.replace(old, new)
foo = s.strip()
foo = s.find(sub, start, end)

I looked at the documentation:

• string.replace vs str.replace
• string.strip vs str.strip
• string.find vs str.find

They look exactly the same. Why were those functions in the string module in the first place? Was it a change before Python 2.7? Is there maybe a performance difference or some special cases which are treated differently?

Judging by the CPython 2.7 string module source, they are trivial wrappers for the method calls. This likely was different in a much older Python. From the initial comments of the same code:

Beginning with Python 1.6, many of these functions are implemented as methods on the standard string object.