Question

Pretty new to Python and have been playing around with lists and the sort member. My question is if I have a list of random strings (all strings of equal length):

li=["hgjtud", "iernfd", "scoeps", "stiiss", "stripe"]

and now I want to sort that list according to some rank which I define with the following function:

def rank_string(str1,str2):
    rank=0
    for i in range(len(str1)): #all strings will be checked to be equal length
        if (str1[i]==str2[i]):
            rank += 1
    return rank

and now I want to sort my list using this function together with a target string, so I try the following:

target_string="stripe"
df = lambda x:rank_string(x,target_string)
sorted_list = resultlist.sort(key=df)

I was of the impression that all list values will be given a key after one pass of the ranking function and thereafter be sorted according to this? This runs, but sorted_list has value None. I assume then that being a n00b, I am missing something fundamental. What? 🙂

Thanks for the help in advance.

Answer 1

The .sort() method sorts in-place and doesn’t return anything.

Use sorted() instead if you want the sorted list returned and the original input list left untouched.

>>> a = [2, 3, 1]
>>> a.sort()
>>> a
[1, 2, 3]
>>> b = [2, 3, 1]
>>> sorted(b)
[1, 2, 3]
>>> b
[2, 3, 1]