Python-列表未转换为元组以进行排序

Question

def mkEntry(file1):
    for line in file1:
        lst = (line.rstrip().split(","))
        print("Old", lst)
        print(type(lst))
        tuple(lst)
        print(type(lst)) #still showing type='list'
        sorted(lst, key=operator.itemgetter(1, 2))


def main():
    openFile = 'yob' + input("Enter the year <Do NOT include 'yob' or .'txt' : ") + '.txt'
    file1 = open(openFile)
    mkEntry(file1)

main()

TextFile:

Emma,F,20791
Tom,M,1658
Anthony,M,985
Lisa,F,88976
Ben,M,6989
Shelly,F,8975

and I get this output:

IndexError: string index out of range

I am trying to convert the lst to Tuple from List. So I will able to order the F to M and Smallest Number to Largest Numbers. In around line 7, it's still printing type list instead of type tuple. I don't know why it's doing that.

Answer 1

    print(type(lst))
    tuple(lst)
    print(type(lst)) #still showing type='list'

You're not changing what lst refers to. You create a new tuple with tuple(lst) and immediately throw it away because you don't assign it to anything. You can do:

lst = tuple(lst)

Note that this will not fix your program. Notice that your sort operation is happening once per line of your file, which is not what you want. Try collecting each line into one sequence of tuples and then doing the sort.

Answer 2

Firstly, you are not saving the tuple you created anywhere:

tup = tuple(lst)

Secondly, there is no point in making it a tuple before sorting it - in fact, a list could be sorted in place as it's mutable, while a tuple would need another copy (although that's fairly cheap, the items it contains aren't copied).

Thirdly, the IndexError has nothing to do with whether it's a list or tuple, nor whether it is sorted. It most likely comes from the itemgetter, because there's a list item that doesn't have three entries in turn - for instance, the strings "F" or "M".

Fourthly, the sort you're doing, but not saving anywhere, is done on each individual line, not the table of data. Considering this means you're comparing a name, a number, and a gender, I rather doubt it's what you intended.

It's completely unclear why you're trying to convert data types, and the code doesn't match the structure of the data. How about moving back to the overview plan and sorting out what you want done? It could well be something like Python's csv module could help considerably.