I see eval as a hacky solution. eval should only ever be used with caution and there's usually a better solution. It's fragile (you may accidentally create invalid code) and can be dangerous (can offer ways for malicious code to be injected). It's also significantly slower, because the python code created by eval has to be recompiled on every iteration.

You can do this more cleanly and safely a couple of ways. You could use getattr(). But I prefer just using function references. Remember that class methods are just functions with an object as the first parameter - true in any OO language but directly visible and usable from Python.

for method in [str.isalnum, str.isalpha, str.isdigit, str.islower, str.isupper]:
    print any(method(c) for c in s)

or

t = type(s)
for method in [t.isalnum, t.isalpha, t.isdigit, t.islower, t.isupper]:
    print any(method(c) for c in s)

Eval is something to use for a quick hack but it's not a good habit.