计算学生的平均绩点GPA的python代码

print(‘welcome to the GPA calculator.’)
print(‘please enter all your letter grades,one per line.’)
print(‘enter a blank line to designate the end.’)
#map from letter grade to point value
points={‘A+’:4.0,‘A’:4.0,‘A-’:3.67,‘B+’:3.33,‘B’:3.0,‘B-’:2.67,‘C+’:2.33,‘C’:2.0,‘C’:1.67,‘D+’:1.33,‘D’:1.0,‘D-’:1.0,‘F’:0.0}
num_course=0
total_points=0
done=False
while not done:
grade = input() #read line from user
if grade==’’: #empty line was entered
done=True
elif grade not in point: #unrecognized grade entered
print("Unknow grade ‘{0}’ being ignored ".format(grade))
else:
num_course+=1
total_point+=points[grade]
if num_course>0: #avoid diversion by zero
print(‘your GPA is {0;.3}’.format(total_points/num_course))