这是我的方法：
import string
import random
import time
response = "a" # the variable that will hold the user's response
c = "b" #the variable that will hold the character the user should type
score = 0 #the variable that will hold the user's score
start = time.time() #the variable that holds the starting time
elapsed = 0 #the variable that holds the number of seconds elapsed.
while elapsed < 30: #while less than 30 seconds have elapsed
if response == c: #if the response from the prevIoUs loop matches the character
score += 1 #from the prevIoUs loop, increase the score.
#c is a random character
c = random.choice(string.ascii_lowercase + string.digits)
print(c)
response = input("Type a letter or a number: ") #get the user's response
elapsed = time.time() - start #update the time elapsed
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