python之多个字符串列表在一起

我有以下两个列表:

Sites = ["iTunes","Google"] 
PurchaseTypes = ["Rental","Purchase"] 

我如何将所有组合相乘，从而产生:

[ 
    "iTunesRental", 
    "iTunesPurchase", 
    "GoogleRental", 
    "GooglePurchase" 
] 

是否有python操作可以做到这一点？或者是否需要为每个列表执行一个 for 循环？即:

combined = [] 
for s in sites: 
    for pt in purchase_types: 
        combined.append(s+pt) 

请您参考如下方法:

使用列表理解:

>>> [a + b for a in Sites for b in PurchaseTypes] 
['iTunesRental', 'iTunesPurchase', 'GoogleRental', 'GooglePurchase']