Yeah... so I agree that's confusing. It's akin to: def x(y=[]): y.append(1) return y for z in range(4): print x() For your c

Yeah... so I agree that's confusing. It's akin to: def x(y=[]): y.append(1) return y for z in range(4): print x() For your case, I recommend using partial functions, which were created for this type of issue. I think it's also cleaner than closures where x depends on an outside context.