- There are parentheses around your first line - this isn't allowed.
- You've haven't used the keyword syntax for your third argument, but you use if for the first two.
Either
log = easygui.multenterbox(msg='Fill in the blanks',title='log', fieldnames=fieldNames)
or
log = easygui.multenterbox('Fill in the blanks', 'log', fieldNames)
would work.
It looks like it'd be useful for you to try typing these commands in an interpreter (open a terminal (search for "Terminal" with spotlight) then type the lines one by one, and look for error you get, or in a terminal type "python yourscript.py" so you can see the error messages. Each of these problems has a helpful error message describing the problem, once you get used to reading these you can debug your own scripts.