For Loop inside Function using a List: not iterating

Hello :) In the typing practice program I am creating in python 3, I have a for...loop that takes the characters from a global list of a certain paragraphs characters and compares it to the character the user is typing. For some reason, the for loop wont iterate and won't go on to the next character. After some research, I figured out that you have to use local variables in order to do this but that doesn't work either. Here is my code:

import random
from tkinter import *
root=Tk()
a_var = StringVar()
words = []
eachword = []
global eachchar
charlist = []
x=random.randint(0,10)

def typingpractice():
    realcharlist = []
    something = []
    paralist = []
    #x=random.randint(0,10)
    file = open("groupproject.txt")
    line = file.readline()
    paraWords = []
    for line in file:
        newline = line.replace("\n","")
        paralist.append(line.replace("\n", ""))
        paraWords.append(newline.split(" "))
    wordList = []
    for c in paraWords[x]:
        charlist.append(c)
    for b in range(0,len(charlist)):
        wordList.append(charlist[b])
        #print (wordList)
        for p in charlist[b]:
            realcharlist.append(p)
    #print(realcharlist)
    a=Canvas(root, width=500, height=500)
    a.pack()
    a.create_text(250,50, text = "Typing Fun", width = 500, font = "Verdana", fill = "purple")
    a.create_text(250,300, text = paralist[x], width = 500, font = "Times", fill = "purple")  
    a = Entry(root, width = 100)
    a.pack()
    a.focus_set()
    a["textvariable"] = a_var


    def compare(s, realcharlist):         
        for g in realcharlist:
            print ("s:",s)
            print ("g:",g)            
            if s == g:
                print ("y")
                a['fg'] = 'green'
                break
            else:
                print ("n")
                a['fg'] = 'red'
                break

    def callback(*args):
        global s
       # print ("b:",xcount)
        s = a.get()
        s = s[-1:]
        compare(s, realcharlist)

    a_var.trace_variable("w", callback) #CALL WHEN VARIABLE IS WRITTEN


def practicetest():
    print ("nothing here yet")

b = Button(root, text="Start Practice", command=typingpractice)
b.pack()

d = Button(root, text="Test", command=practicetest)
d.pack()

root.mainloop()

The text file "groupproject.txt" is an external text file that contains 10 one-line paragraphs, each character of each paragraph is being compared to what the user is typing in.

Any help on how to make the for loop work would be greatly appreciated. Thanks :D