Finding nth position of substring in a string using python

Question

Let's take example string, 'I am programmer and I am doing coding. I am interested in it' and the target word (substring) is 'am'. I want to find nth value of it where it is located by the complete words, not indexes. For example, substring 'am' is located on 2nd, 6th and 10 position. I tried searching but all the results were relevant to finding indexes. One I found about nth value didn't work for me. Code was giving error on ':' of 'IF'.

    parts= haystack.split(needle, n+1)
    if len(parts)<=n+1:
        return -1
    return len(haystack)-len(parts[-1])-len(needle)

Do you have an optimum and simple solution for this. I am trying to just solve the problem with possible solutions and logics. Your cooperation will be well appreciated.

So you only want to match entire words, is that correct? Otherwise "programmer" would match "am". — Tom Karzes, May 08 '21 at 04:20
Does this answer your question? [How to find all occurrences of an element in a list](https://stackoverflow.com/questions/6294179/how-to-find-all-occurrences-of-an-element-in-a-list) (where the list is the result of `haystack.split(" ")`) — SuperStormer, May 08 '21 at 04:22
@TomKarzes Yes. In short I wanna find the whole word with it's position according to words on nth position. — Syed Ali Zain Naqvi, May 08 '21 at 04:25
Does this answer your question? [Find the nth occurrence of substring in a string](https://stackoverflow.com/questions/1883980/find-the-nth-occurrence-of-substring-in-a-string) — deadshot, May 08 '21 at 04:29
@SuperStormer I tried with following code using the link you shared. ```#!/bin/python3 def FindNthTargetString(string, target): counter=0 lst=[] if target in string: li=list(string.split(" ")) j = [i for i, x in enumerate(li) if x == target] print("Positions of string ",target," is :-") for s in range(len(j)): print(j[s]+1) else: return "Target word not in the string." It worked well with this string, not for "Today is my sessional exam. I am not fully prepared for exam. I don't know, how I will perform in exam" — Syed Ali Zain Naqvi, May 08 '21 at 04:37

score 1 · Answer 1 · answered May 08 '21 at 04:29

You can do something like this.

string = 'I am programmer and I am doing coding. I am interested in it'.split()
target = 'am'
for count,words in enumerate(string):
    if words == target:
        print(count)

This will give you 1,5,9. This is because indexes start from zero. Now ofcourse if you want 2,6,10 you can just add one to count whenever it is printed.

list comprehension

string = 'I am programmer and I am doing coding. I am interested in it'.split()
target = 'am'
wordPlace = [count for count,words in enumerate(string) if words == target]

Thank you for the answer. The code above, it returned me **22** with the string **Today is my sessional exam. I am not fully prepared for exam. I don't know, how I will perform in exam** and finding target word **exam**. The desired output is 4, 11 and 20 on this string mentioned. — Syed Ali Zain Naqvi, May 08 '21 at 05:05

Syed Ali Zain Naqvi · Answer 2 · 2021-05-08T05:01:56.510

I tried following code and it worked on the string below where the function is called.

    counter=0
    lst=[]
    if target in string:
        li=list(string.split(" ")) #li is list, string to list
        j = [i for i, x in enumerate(li) if x == "exam"]
        print("Positions of string ",target," is :-")
        for s in range(len(j)):
            print(j[s]+1)


    else:
        return "Target word not in the string."

print(findTargetWord("Today is my exam and exam is easy", "exam")) #it worked on this string

I tried string Today is my sessional exam. I am not fully prepared for exam. I don't know, how I will perform in exam. Instead of returning me the correct answer, it print 21.

Finding nth position of substring in a string using python

2 Answers2