'TypeError: list indices must be integers, not str' Python 3

Question

I need a bit of help with this assignment (first time posting on SE so please excuse my lack of posting etiquette if any)

So for this code I had to write a spell checker. Basically what it is supposed to do is:

1.) Check through two lists (One is a dictionary, where we get all the correctly spelled words, the other is the user input list which should have an incorrectly spelled word or two)

2.) suggest a correct word in place of the misspelled word (example would be if I spelled heloo, the spell checker would say i spelled that wrong and would suggest the word is hello, help, etc.)

My biggest problem right now is at line 19, I am getting the list indices must be integers problem.

Any help is appreciated, and help with finishing this would also be much appreciated! I feel like outside of the syntax more could be improved upon. Thanks.

here is the code, it is not completely finished

import re

def words_from_file(filename):
try:
    f = open(filename, "r")
    words = re.split(r"[,.;:?\s]+", f.read())
    f.close()
    return [word for word in words if word]
except IOError:
    print("Error opening %s for reading. Quitting" % (filename))
    exit()


user_word = words_from_file('user_word.txt')
suggestion = words_from_file('big_word_list.txt')
sug_list = []

for a in user_word:
    if user_word[a] not in suggestion:
        print ("Spelling error: %s"%(user_word[a]))
        for i in suggestion:
            for j in suggestion[i]:
                if len(suggestion[i][j]) == len(user_word[a]-2):
                    count = 0
                    similarities = len(user_word[a])
                    for k in suggestion[i][j]:
                        if suggestion[i][j][k] in suggestion:
                            count+=1
                            if count >= similarities:
                                sug_list.append(suggestion[i][j])

Answer 1

Change:

for a in user_word:
    if user_word[a] not in suggestion:

Into:

for a in user_word:
    if a not in suggestion:

because all items in user_word list will be iterated using the a variable. The a will in each iteration contain a nonempty string obtained from the line split. You can only use numerical index with a list type. Originally you've used a string in place of numeric index which causes the error message.

Answer 2

List can slice using integers not str

Change

if user_word[a] not in suggestion: #to==> if a not in suggestion:

for j in suggestion[i]: #to==> for j in i

for k in suggestion[i][j]: #to==> for k in j

Also many errors slice errors like suggestion[i][j][k] etc

So generally

for i in [1,2,3]:
    print(i) # gives 1,2,3.No need of [1,2,3][i]

Also, you can use range(len)

for a in range(len(user_word)):
    if user_word[a] not in suggestion: