How to make my code work more efficiently - python-3.x

Question

I made this grade calculator that calculates the grade form my school website. There are some minor flaws that do not affect the code, but does bug me. For example, When I paste the grade from the website, I have to press enter twice, which people who are using my program for the first time get confused with. Also, I want to make it so that the code does not create errors when I press enter without any data given in input.
Not only, these, but I want some feedback on my code and how I can improve them.
This is the code I worked on so far.
class color:
reset = '\\033\[0m'
class fg:
green = '\\033\[32m'
orange = '\\033\[33m'
\#getting input from user
def multi_input():
try:
while True:
data=input(color.fg.orange)
if not data: break
yield data
except KeyboardInterrupt:
return
restart=1
while restart!="x":
score = \[\]
percent = \[\]
add = \[\]
print(color.fg.green + "Enter Grade" + color.reset)
data = 0
data = list(multi_input())
#filter data into percent and score
for i in range(3, len(data),4):
data[i] = data[i].split('\t')
try:
percent.append(data[i][3])
score.append(data[i][4])
except IndexError:
result = 0
#take out ungraded values
percent = [value for value in percent if value != '']
score = [value for value in score if value != '']
#refine percent data
for i in range(len(percent)):
try:
percent[i] = percent[i].replace('%', '')
percent[i] = float(percent[i])
except ZeroDivisionError:
result = 0
#refine score data
for i in range(len(score)):
score[i] = score[i].split('/')
for j in range(len(score[i])):
score[i][j] = float(score[i][j])
try:
score[i] = score[i][0]/score[i][1]*100
except ZeroDivisionError:
result = 0
#amount of assignments
print()
print(color.fg.green + "graded assignments: ", len(score))
#calculation
for i in range(len(score)):
add.append(score[i]*percent[i]/100)
print(color.fg.green + "Percentage: ", f"{sum(add)/sum(percent)*100:05.2f}" + color.reset)
restart = input(color.fg.green + "press any key to start again, or x to exit.")
print()
This is a sample grade copied from my school website so that you can test my code out.
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