Random Password Generator based on user input
At the top of the module use triple quotes to document things instead of using comments. At the top level it will also act as a docstring for your module.
Use random.choice on the iterable instead of getting a random int first and then using it get an from iterable.
if answer == "Y" or answer == "y" etc can be replaced with if answer.lower() == "y".
Use better variables names, for example a and b in FunRun(a, b) doesn't make any sense.
Use new style string formatting instead of the old sprintf based syntax. Or better join str.join in your case if you want to merge bunch of items.
Your code has too many PEP 8 issues as per PEP8 online tool. You should check PEP 8 and use extensions like flake8, pylint etc to catch those.