在函数中调用参数（Python）

我是python新手，我只是在尝试制作我的第一个程序来计算某人在期末考试中需要得到什么，以获得类似于rogerhub的目标分数。我有一个公式可以工作，但似乎无法调用函数中的参数而不出错。正如我所说，我刚刚开始学习python，所以我确信这只是一个简单的错误。任何帮助都将不胜感激

current_grade = float(raw_input("Your current grade is:"))
target_grade = float(raw_input("You want at least a :"))
final_percentage = float(raw_input("Your Final is worth:"))
final_percentage = (final_percentage / 100)
semester_percentage = 1 - (final_percentage)


def class_grade(current_grade, target_grade, final_percentage):
    grade_needed = ((target_grade - current_grade * (1 - final_percentage))/ final_percentage)
    return grade_needed

def main():
    pass

if __name__ == '__main__':
    main()

class_grade(current_grade, target_grade, final_percentage)

print "In order go get %s your need to get a %s on your final" % (target_grade, class_grade)

""" Formula for program

Insert your known numbers into the following formula:
G= (D-C(1-P))/P

G is the grade you will need on the final test.
C is the grade you're currently carrying in the class.
D stands for what your school has determined as a passing grade. This should be 60 or 70.
P is the percentage of the total grade for which the final test counts.
Both C and D should be whole numbers, while a decimal should be used for P.
"""

等级是一个函数。要使其运行，必须将其参数放在括号中：

班级成绩当前成绩、目标成绩、最终成绩百分比

最终结果是：

print "In order go get %s your need to get a %s on your final" % (target_grade, class_grade(current_grade, target_grade, final_percentage))

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你能发布错误吗？当然，当我打印它的时候，这就是我得到的，为了得到82.0，你需要得到一个关于你的最终结果的提示：你不需要Python中的main函数。你也可以把它和if uuu name uuuuu=='uuuu main uuuuuuuu'部分都去掉，效果很好。真希望我能自己弄明白，但非常感谢！