Ответ:

Python 3.7.2

def readFile(file):

   with open(file, 'r',  encoding = 'utf-8') as file:

       text = file.readlines()

   return text  

file = input('Enter path to file: ')

text = ' '.join(readFile(file))

most_word = ['', 0]

for word in text.split(' '):

   if most_word[1] < text.count(word):  

       most_word[0] = word; most_word[1] = text.count(word)

print(most_word)