how to write back the sorted lines of a file in alphanumerical order

Question

def sortall(string):
    if not string:
        return []
    return (sortall([x for x in string[1:] if x < string[0]])
            + [string[0]] +
            sortall([x for x in string[1:] if x >= string[0]]))


file = open("sorting.txt", "r+")
for line in file.readline():
    xd = (''.join(sortall(line)))
    file2 = open("sorting.txt", "w")
    file2.write(xd)

how do i make it my code print the sorted file lines, but when it does, it does it in ascending order.

Answer 1

read whole file, sort and write into new file:

with open('file1', 'r') as f:
    lst = f.readlines()
    with open('file2', 'w') as w:
        w.writelines(sorted(lst))

if "sorted" should use some special sorting, provide comparing function in "key" argument:

print(help(sorted))

sorted(iterable, /, *, key=None, reverse=False)
Return a new list containing all items from the iterable in ascending order.

A custom key function can be supplied to customize the sort order, and the reverse flag can be set to request the result in descending order.

Answer 2

This is a more concise way to do it:

with open('sorting.txt', 'r+') as f:
    sorted_lines = sorted(f.readlines())
    f.writelines(sorted_lines)

As you can see here: https://docs.python.org/3/howto/sorting.html , you can provide a callable in order to customize the ordering.

sorted(iterable, /, *, key=None, reverse=False)
Return a new list containing all items from the iterable in ascending order.

A custom key function can be supplied to customize the sort order, and the reverse flag can be set to request the result in descending order.