Joe Poniatowski wrote: #- >>> ls = [] #- >>> def f1(l2=[]): #- ... l2 = ['word1','word2'] #- ... print l2 #- ... #- >>> f1(ls) #- ['word1', 'word2'] #- >>> ls #- [] #- >>> When you pass ls to f1, you're pointing l2 to ls. Then, you point l2 to ['word1','word2']. But ls is still pointing to [] (you never changed that). . Facundo