You may try using word-boundaries around your text. Something like:

\bhello\b

You can find the demo of the above regex in here.

Sample implementation in Python

import re
def find_string(file_name, word):
   with open(file_name, 'r') as a:
       for line in a:
           line = line.rstrip()
           if re.search(r"\b{}\b".format(word),line):
             return True
   return False

if find_string('myfile.txt', 'hello'):
    print("found")
else:
    print("not found")

You can find the sample run of the above implementation in here.

You can use the word-boundaries of regular expressions. Example:

import re

s = '98787This is correct'
for words in ['This is correct', 'This', 'is', 'correct']:
    if re.search(r'\b' + words + r'\b', s):
        print('{0} found'.format(words))

That yields:

is found
correct found

For an exact match, replace \b assertions with ^ and $ to restrict the match to the begin and end of line.

you could use regular expression for this, reading the strings an defining the rules for that, in this particular case, either there is a separator or the end of the string so the following code might solve your problem:

import re

# Sample string representing the text to search
string = "featureSetCombination: 1 \n featureSetCombination: 10"

re.findall("featureSetCombination:[1-9][$|\s|.|,|;]", string)
>> ['featureSetCombination:1,']

as you can see it finds the first occurrence but not the second

For this kind of thing, regexps are very useful :

import re

print(re.findall('\\blocal\\b', "Hello, locally local test local."))
// ['local', 'local']

\b means word boundary, basically. Can be space, punctuation, etc.

Edit for comment :

print(re.sub('\\blocal\\b', '*****', "Hello, LOCAL locally local test local.", flags=re.IGNORECASE))
// Hello, ***** locally ***** test *****.

You can remove flags=re.IGNORECASE if you don't want to ignore the case, obviously.

This is another approach to take to complete your task, it may be helpful although it doesn't follow your current approach very much.

The test.txt file I fed as input had four sentences:

This is a special cat. And this is a special dog. That's an average    cat. But better than that loud dog.

When you run the program, include the text file. In command line, that'd look something like:

python file.py test.txt

This is the accompanying file.py:

import fileinput

key = raw_input("Please enter the word you with to search for: ")
#print "You've selected: ", key, " as you're key-word."

with open('test.txt') as f:
    content = str(f.readlines())

#print "This is the CONTENT", content

list_of_sentences = content.split(".")
for sentence in list_of_sentences:
    words = sentence.split(" ")
    for word in words:
        if word == key:
            print sentence

For the keyword "cat", this returns:

That is a special cat
That's an average cat

(note the periods are no longer there).

Its because of that you check witht in operation (if i in line) you need to check with == but as line has a \n at the trailing you need to add one \n at the end of your words.

if i+'\n' == line

Try this.

with open('id_list.txt', 'r') as stream:
    ids = stream.read()
    words = ids.strip().split()
    keywords = ['admin','admin123','rtadmin']  
    for item in keywords:  
        if item not in ids:
            print("Do something")