Python error TypeError unsupported operand type s for - list and int

Question

I am trying to understand the markov chain. This is my code:

import numpy as np
import random as rm
#import io

trump = open('C:\Users\sharma\PycharmProjects\machine-learning\speeches.txt').read()
# display the data
#print(trump)

#split the data
corpus = trump.split()
#print(corpus)

#Make pairs
def make_pairs(corpus):
    for i in range(len(corpus) - 1):
        yield (corpus[i] , corpus[i + 1])
pairs = make_pairs(corpus)

#append dictionary
word_dict = {}
for word1, word2 in pairs:
    if word1 in word_dict:
        word_dict[word1].append(word2)
    else:
        word_dict[word1] = [word2]

#Randomly pick first word
first_word = np.random.choice(corpus)
while first_word.islower():
    chain = [first_word]
    n_words = 20
    for i in range(n_words):
        chain.append(np.random.choice(word_dict[chain - 1]))
        print (' '.join(chain))

Ending up with the following error:

chain.append(np.random.choice(word_dict[chain - 1]))
TypeError: unsupported operand type(s) for -: 'list' and 'int'

Answer 1

Hey, look at your code's second last line, you are trying to subtract an integer from a list which is obviously wrong.

According to your logic, I think this is what you are looking for:

chain.append(np.random.choice(word_dict[chain[-1]]))

Hope this helps!!

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Thanks!