Touch Typing with Python

tt.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import time
import random

def interval():
    start_time = time.time()
    def end_time():
        return time.time() - start_time
    return end_time

def word(level):
    chars = "fjdkslaghvmcxzbnrueiwoqpty"
    n = ""
    for x in range(5):
        n += chars[random.randrange(0, level)]
    return n

def problem_line(level):
    w = []
    for x in range(8):
        w.append(word(level))
    return ' '.join(w)

def difference(problem_line, enter_line):
    d = ""
    for i in range(len(problem_line)):
        if i < len(enter_line):
            if problem_line[i] == enter_line[i]:
                d += ' '
            else:
                d += problem_line[i]
    return d

def count_wrongs(diff_line):
    return len(diff_line) - diff_line.count(' ')

def main(initial_level):
    min_level = 2
    if min_level <= initial_level:
        level = initial_level
    else:
        level = min_level
    while True:
        print("level: %d" % level)
        problem = problem_line(level)
        print(problem)
        inter = interval()
        enter_line = input().ljust(len(problem))
        diff_line = difference(problem, enter_line)
        wrongs = count_wrongs(diff_line)
        print(diff_line)
        if enter_line == "":
            pass
        else:
            if wrongs < 2 and inter() < 25:
                level = level + 1
            if 3 <= wrongs and 2 < level:
                level = level - 1 

if __name__ == '__main__':
    main(2)