count particular word in python code example

Example: count word per sentence python

import nltk
#nltk.download('punkt')
from nltk.tokenize import sent_tokenize

def count_lines(file):
    count=0
    myfile=open(file,"r")
    string = ""

    for line in myfile:
        string+=line  
        print(string)

    number_of_sentences = sent_tokenize(string)

    for w in number_of_sentences:
        count+=1
        print("Sentence ",count,"has ",len(w),"words")

count_lines("D:\Atharva\demo.txt")