对列表中文件的单词进行排序

Question

I am trying to sort all the words of a text file in alphabetical order. Here is my code:

filename=input('Write the name of the file :')
fh=open(filename)
wlist=list()
for line in fh:
    line=line.rstrip()
    ls=line.split()
    for w in ls:
        if w not in wlist:
        wlist.append(w)            
print(wlist)

The output is ok but whenever I try print(wlist.sort()) it gives 'None' as output instead of sorting the wlist.what is the problem in my code?

Thanks in advance.

Answer 1

list.sort sorts the list in-place and returns None .
If you want to print the sorted list, do it afterwards:

wlist.sort()
print(wlist)

Separately, instead of checking the list for duplicates every time it'd be far more efficient to make a set of the words, and then sort that with sorted() :

words = set()
for line in file:
    for word in line.split():
        words.add(word)

print(sorted(words))

Answer 2

There were some indentation inconsistencies but other then that its good. As a general rule the function sort() only performs the ordering of items in the list. If you want to return the list print it:

filename=input('Write the name of the file :')

wlist = []
# I would recommend opening files in this format
with open(filename) as f_obj:
   read = f_obj.readlines()

for line in read:
    ls = line.split(' ')
    for w in ls:
        if w not in wlist:
            wlist.append(w)

wlist.sort()               
print(wlist)