在Python的字符串/列表中获取第三大单词

Question

For the code below i can't seem to get the 3rd largest word. I am splitting the string i get from user input and putting it in the "words" var, then i make 2 lists - one of which includes the words sorted in terms of length.

Then i get the length of the longest word (in maxlist ) and second longest word (in maxlist2 ) and remove them. All that's left should be the third longest word from the original list and any shorter words. But i find it doesn't quite work right.

The second and third "for" statements below don't seem to remove all instances of wordlength represented by "maxlist"

For example, if i represent words by just the letter "e" and use different numbers of e's for different wordlength (ie. ee, eeee, eeeee) some of these instances are removed by the "for" statement and some are not. For this input: "e ee eee eeee eeee eeee eeee eeee eeee eeee eeee" i should expect all "eeee" words to be removed by the code:

 if len(word) == maxlist:
            sort2.remove(word)

If i repeat the code again for the next longest word (which is done by the third "for" statement) i should also remove the "eee" instance. They are not removed though, and the final list remains "'e', 'ee', 'eee', 'eeee', 'eeee'"

The second "for" statement seems to remove 6 instances of "eeee" but not all 8 instances. What is wrong here? Please help!!

My final output should be the third longest word of the original list + any shorter words.

def ThirdGreatest(strArr):

    words = strArr.split()
    sort=[] # length of words
    sort2=[] # actual words
    for word in words:
        sort2.append(word)
        sort.append(len(word))
        sort2.sort()

    maxlist= len(max(sort2, key=len)) 
    for word in sort2:
        if len(word) == maxlist:
            sort2.remove(word)

    maxlist2 = len(max(sort2, key=len))
    for word in sort2:
        if len(word) == maxlist2:
            sort2.remove(word)

    maxlist3 = (max(sort2, key=len))

    print 
    print "biggest word is {} char long ".format(maxlist) 
    print sort
    print "3rd biggest word is {}: ".format(maxlist3)
    print "3rd biggest word is {}: ".format(sort2) # list of words remaining       
    #after the first 2 longest have been removed


ThirdGreatest(raw_input("Enter String: ")) 

Answer 1

You should use heapq for finding the third largest:

third_largest = heapq.nlargest(3, set(words))[-1]

After that, you can use all sorts of stuff, eg list comprehension:

[word for word in words if word != third_largest]

Answer 2

Your problem is:

for word in sort2:
    if len(word) == maxlist:
        sort2.remove(word)

Don't change the list you're currently iterating, that's just gonna mess things up. It's like you're reading a book and someone rips out pages while you're reading.

Iterate over a copy instead:

for word in sort2[:]:
    if len(word) == maxlist:
        sort2.remove(word)

Note the added [:] , which gives you a copy.

---

And an alternative solution :

[next(g) for _, g in groupby(sorted(words, key=len), len)][-3]

Demo:

>>> words = 'This is a test and I try hard to make it good'.split()
>>> from itertools import groupby
>>> [next(g) for _, g in groupby(sorted(words, key=len), len)][-3]
'is'

Answer 3

This was my original, long and cumbersome solution but other users have posted much more concise and clear answers. Thank you guys.

Def ThirdGreatest(strArr): words = strArr.split() sort=[] # length of words sort2=[] # actual words

for word in words:
    sort2.append(word)
    sort.append(len(word))

sort3=set(sort2)
sorted_set3= sorted(sort3, key=len)
sort4 =[]
for n in sorted_set3:
    sort4.append(n)

maxlist= len(max(sort4, key=len)) 
for word in sort4:
    if len(word) == maxlist:
        sort4.remove(word)

maxlist2 = len(max(sort4, key=len))
for word in sort4:
    if len(word) == maxlist2:
        sort4.remove(word)
print "_______________________________________________________________"
print "The third largest word is: {} ".format(max(sort4, key=len))

ThirdGreatest(raw_input("Enter String: "))