python之迭代嵌套列表并更改值

我试图找到这个答案，但只能找到我难以拼凑的碎片。

假设我有:

aList = [["星期一", "2.03","4.03"],["星期二","4.03","5.03"],["星期三","3.2","4.3"] ]

我想遍历这个嵌套列表并将编号的字符串值更改为 float 。

请您参考如下方法:

aList = [["Monday", "2.03","4.03"], 
         ["Tuesday","4.03","5.03"], 
         ["Wednesday","3.2","4.3"]] 
 
def helper(s): 
    try: return float(s) 
    except ValueError: return s 
 
aList[:] = [[helper(item) for item in subl] for subl in aList] 
print aList 

输出:

[['Monday', 2.03, 4.03], ['Tuesday', 4.03, 5.03], ['Wednesday', 3.2, 4.3]]