Getting the position of an item in a list from an input (Python)

Question

I have a list with words in it. I want to get the position of the word in the sentence that the user asks for. (I am using python) For example if I had the sentence: "Hello world how are you doing today world?" 'World' occurs in the first and eighth positions. If a user wants to know the positions of the word 'world' in that sentence it would print "The word world is in position 1 and 8". I am aware of the enumerate method but cannot get it to work with an input or an elif statement. I want to get the position(s) of any word in the sentence no matter how many times the word occurs.

`word = input("Enter word: ").strip().lower()` and `answer = [i for i,w in enuemrate(sentence.lower().split()) if w==word]` — inspectorG4dget, Jan 25 '16 at 21:23
@inspectorG4dget your code was my first attempt too, but it does not find 'world' in 'world?' but the specs say it should. — timgeb, Jan 25 '16 at 21:25
@timgeb: that's because `world?` and `world` are not the same. You'd therefore have to include ONLY the elements of `string.ascii_lowercase` — inspectorG4dget, Jan 25 '16 at 21:32
@inspectorG4dget I know? The specifications in the question say it should find 'world' in 'world?' regardless. That's why we need a regex. — timgeb, Jan 25 '16 at 21:34
you shouldn't need a regex. Just filter your sentence like this: `sentence = ''.join([char for char in sentence if char in string.ascii_lowercase + ' '])`. Don't forget to `import string` — inspectorG4dget, Jan 25 '16 at 21:35

Eugene Yarmash · Answer 1 · 2016-01-26T07:38:06.443

2

You could extract the words using a regular expression, then use enumerate() in a list comprehension to find the indexes of the word:

>>> import re
>>> s =  "Hello world how are you doing today world?"
>>> word = input("Enter a word: ").lower()
Enter a word: world
>>> [i for i, v in enumerate(re.findall(r'\w+', s)) if v == word]
[1, 7]

edited Jan 26 '16 at 07:38

answered Jan 25 '16 at 21:26

Eugene Yarmash

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score 2 · Accepted Answer · answered Jan 26 '16 at 01:50

2

sentence = "Hello world how are you doing today world?".lower()
searchword = input("Enter word:  ").lower()

newsentence = ''

for character in sentence:
    if character.islower() or character == ' ': newsentence += character

answer = [position for position, word in enumerate(newsentence.split()) if searchword == word]

print(answer)

answered Jan 26 '16 at 01:50

Michael

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I have used your method but it uses the wrong positions. For example 0 when it should be 1. I know why this occurs. I have tried adding 1 to answer but that just caused an error. I was wondering if you know a solution? – Jan 27 '16 at 23:29
List start at position 0. Hello is in position 0 in "Hello world". I won't recommend it but if it is necessary I would just change answer to below. answer = [position + 1 for position, word in enumerate(newsentence.split()) if searchword == word] – Michael Jan 29 '16 at 01:41

score 0 · Answer 3 · edited Mar 20 '16 at 16:43

0

In your sentence, the word "world" appears in position 1 and 7.

> sentence = "Hello world how are you doing today world?"
> word = input("Enter word:  ").lower()
> answer = [i for i, w in enumerate(sentence.lower().split()) if word in w]
> answer
> [1, 7]

This will work regardless of case or punctuation.

edited Mar 20 '16 at 16:43

planetp

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answered Jan 25 '16 at 21:57

SeanS

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This will also print the positions of words for which the word is a substring, e.g. `"worlds"`. – Eugene Yarmash Jan 25 '16 at 22:11
or `"otherworldly"`, should these words really be counted? – timgeb Jan 25 '16 at 22:36
Yup. The re solutions look good, or if R.McEvoy doesn't want to use re, the @Michael solution looks good. – SeanS Jan 26 '16 at 15:07

score -1 · Answer 4 · answered Jan 25 '16 at 21:30

With re.finditer and enumerate:

>>> import re
>>> s='Hello world how are you doing today world?'
>>> word='world'
>>> [i for i, w in enumerate(re.finditer('\w+', s)) if w.group()==word]
[1, 7]

We (greedily) find every sequence of characters delimited by non-word characters, iterate over it, and store the index if it is equals to the target word.

score -1 · Answer 5 · answered Jan 25 '16 at 22:09

-1

 import re
 s='Hello world how are you doing today world?'
 word='world'
 [i for i, w in enumerate(re.findall('\w+', s)) if w.lower() == word.lower()]

answered Jan 25 '16 at 22:09

FatmaT

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Getting the position of an item in a list from an input (Python)

5 Answers5