exec-function in Python 3.+

[Hans Larsen]

Help!
    I'm begginer in Python 3.+!
    If i wih to update a module after an import and chages,
    How could I do:
    By "from imp import reload" and then reload(mymodule)
    or how to use "exec(?)", it is mentoined in docs.
    In Python ver. <3 reload(module) writes something back to interpretter!, 
how about exec, which is a function?-:)
    I,m thanking on the help!!