Filter a list in Python

I have a list in Python ['var1', 'var2', 'var3, 'var4'], ['var1', 'var2', 'var3, 'var4'] etc..

I want to filter that list based on criteria, like var1=3, var2=5, var3='', var4=6. If the filter (example var3) is empty, then show all based on the other criterias.

Tips?