Is there a way to delete created variables, functions, etc from the memory of the interpreter?

You can delete individual names with del:

del x

or you can remove them from the globals() object:

for name in dir():
    if not name.startswith('_'):
        del globals()[name]

This is just an example loop; it defensively only deletes names that do not start with an underscore, making a (not unreasoned) assumption that you only used names without an underscore at the start in your interpreter. You could use a hard-coded list of names to keep instead (whitelisting) if you really wanted to be thorough. There is no built-in function to do the clearing for you, other than just exit and restart the interpreter.

Modules you've imported (import os) are going to remain imported because they are referenced by sys.modules; subsequent imports will reuse the already imported module object. You just won't have a reference to them in your current global namespace.

Yes. There is a simple way to remove everything in iPython. In iPython console, just type:

%reset

Then system will ask you to confirm. Press y. If you don't want to see this prompt, simply type:

%reset -f

This should work..

You can use python garbage collector:

import gc
gc.collect()