Why 'string' functions i.e. rstrip, upper, lower are 'not found'.........

[John F Dutcher]

There must be a 'fundamental' reason why 'string' functions are
reported as 'not found' even though the 'import string' statement
is present. If the script has user-defined functions at its beginning
and I remove them...doing all code inline, the 'not found' error goes away.
Is there some 'placement of user functions' issue that explains why
the 'import string' doesn't make the various string functions visible
when I use various 'def userfunc's in the script ??
Thanks much,
John D.