CODEWITHSUNDEEP
pythonstringpython-3.xfor-loopindexing
LukeP_8
LukeP_8

Reputation: 309

Find words in a sentence and its index position using a for loop

I am writing a code that prompts the user to enter a sentence which is then defined as str1 and then is prompted to enter a word defined as str2.

For example:

Please enter a sentence: i like to code in python and code things
Thank you, you entered:  i like to code in python and code things
Please enter a word: code

I want to use a for loop to find str2 in str1 to print whether the word is or is not found, and if it has been found, the index position(s) of str2.

Currently I have this code:

str1Input = input("Please enter a sentence: ")
print("Thank you, you entered: ",str1Input)

str1 = str1Input.split()

str2 = input("Please enter a word: ")

if str2 in str1:
    for str2 in str1:
        print("That word was found at index position", str1.index(str2)+1)
else:
    print("Sorry that word was not found")

Although, the outcome appears to print whether or not the index position was found but then prints the index position of every word inside the sentence. Also if I am searching of a certain word that appears twice in that sentence, it just prints the index position of the first time the word is seen in the sentence, for example:

Please enter a sentence: i like to code in python and code things
Please enter a word: code
Thank you, you entered:  i like to code in python and code things


That word was found at index position: 1
That word was found at index position: 2
That word was found at index position: 3
That word was found at index position: 4
That word was found at index position: 5
That word was found at index position: 6
That word was found at index position: 7
That word was found at index position: 4
That word was found at index position: 9

If anyone could help me and anyone else attempting something similar to this that would be extremely helpful!

Upvotes: 1

Views: 11777

Answers (5)

NicheQuiche
NicheQuiche

Reputation: 82

Just make sure to use comparisons in if/else statements and think about what your loop is doing.

Hope this is simple enough but effective:

EDIT: Add a counter rather than using ".index()". Just keeps it nice and basic:

str1In = "I like to code a few things and code a lot"
str2 = "code"
str1 = str1In.split()

indexCount = 0
for word in str1:
    if word == str2:
       print("Your word was found at index point",int(indexCount))
    else:
       print("Your word was not found at",int(indexCount))
    indexCount += 1

Upvotes: 0

Ajax1234
Ajax1234

Reputation: 71451

What you can do is make a list out of str1 and find where str2 occurs in the list. Here is the code:

   str1 = "i like to code in python and code things"
   str2 = "code"

  the_indexes = []
  the_new_list = [str1.split(' ')]


  the_count = str1.count(str2)
  if the_count > 0:



  for i in range(len(the_new_list[0])):
       if the_new_list[0][i] == str2:
           the_indexes.append(i)

  else:
      print str2, " not found in the first sentence"

  print "The indexes are: "

  for i in the_indexes:
       print i

Upvotes: 0

Denis Olehov
Denis Olehov

Reputation: 192

Use the enumerate python built-in function:

for index, word in enumerate(splitted_sentence):
   if word == target_word:
       print("Index: ", index)

docs: https://docs.python.org/3.3/library/functions.html#enumerate

UPD: list.index() method returns the lowest index of matching element. That's why you always get same index if your word appears twice in a sentence.

Check the docs on this as well: https://docs.python.org/3.6/tutorial/datastructures.html#more-on-lists

Upvotes: 2

MSeifert
MSeifert

Reputation: 152637

You can use a conditional list comprehension (it's like a for-loop):

>>> str1 = 'i like to code in python and code things'
>>> str2 = 'code'

>>> indices = [idx for idx, word in enumerate(str1Input.split(), 1) if word == str2]
>>> indices
[4, 8]

Giving you the indices of the matches. Then you can do whatever you like with those:

if indices:
    for idx in indices:
        print('word found at position {}'.format(idx)
else:
    print('word not found')

Your attempt actually wasn't too bad but you did one mistake: for str2 in str1: this overwrites your str2 variable which holds the string to look for! Also index will always give you the first index of your variable so when you did str1.index(str2)+1 you looked for the first occurence of the currently investigated item! That's why you had That word was found at index position: 4 two times because it only looked for the first 'code'.

The documentation is always useful to read:

list.index:

Return the index in the list of the first item whose value is x. It is an error if there is no such item.

Upvotes: 2

Reaper
Reaper

Reputation: 757

Your problem is in for loop: you assign values from str1 to local variable str1 each iteration. It's called variable shadowing. The solution is to use different variable name in loop declaration.

Upvotes: 0

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