TypeError:%不支持的操作数类型：“Text”和“tuple”

Question

我正在做一个程序来计算缺课的费用。我把学费、课程数和一学期的周数作为变量，然后绘制结果（使用Python2.7）。这是我一直在研究的代码：

import matplotlib.pyplot as plot

def calculations(t, c, w, wk):

    two_week = (((t/c)/w)/2)*wk
    three_week = (((t/c)/w)/3)*wk
    return two_week, three_week

def main():
    tuition = float(raw_input('Tuition cost (not including fees): '))
    courses = int(raw_input('Number of courses: '))
    weeks = int(raw_input('Number of weeks in the semester: '))
    x_axis = range(0,10)
    y_axis = []
    y_axis2 = []
    for week in x_axis:
        cost_two, cost_three = calculations(tuition, courses, weeks, week)
        y_axis += [cost_two]
        y_axis2 += [cost_three]

    plot.plot(x_axis, y_axis ,marker='o', label='course meets 2x a week', color='b')
    plot.plot(x_axis, y_axis2,marker='o', label='course meets 3x a week', color='g')
    plot.xlabel('number of missed classes')
    plot.ylabel('cost ($)')
    plot.title('Tuition: %.2f Courses: %d Weeks in a semester: %d\n Created by <MyName>') %(tuition, courses, weeks)
    plot.legend()
    plot.xticks(x_axis)
    plot.xlim(0,x_axis[-1]+1)
    plot.yticks(y_axis)
    plot.ylim(0, y_axis[0]+1)
    plot.grid()
    plot.show()
    plot.savefig('missing-class-cost.pdf')

main()

但是，每当我运行程序时，都会收到以下错误：

Traceback (most recent call last):
  File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 36,     in <module>
  File "C:\Program Files (x86)\Wing IDE 101 4.1\src\debug\tserver\_sandbox.py", line 26, in main
TypeError: unsupported operand type(s) for %: 'Text' and 'tuple'

第26行是指这一行代码：

plot.title('Tuition: %.2f Courses: %d Weeks in a semester: %d\n Created by <MyName>') %(tuition, courses, weeks)

我想是因为一些数学问题，但我没有在整个程序中使用元组，所以我有点不知所措。

感谢您的帮助。