退出菜单的最简单方法

Question

我完成了所有的作业，但我忘了在子菜单下面加一个取消选项。我不想修改所有的文件，因为这花了我两天时间。请问在sub_menu.py里，最简单的方法是什么，能加一个取消和返回主菜单的选项？

这是sub_menu.py的内容

#!/usr/bin/python

## sub_menu.py

#=========#=========#=========#=========#=========#=========#=========#
def how_many():
    while True:
        print
        print "  How many do you want to draw? -----Range is from 1 to 5-----"
        shape_num = raw_input('  Enter your choice: ')
        try: 
            shape_num = int(shape_num)
            if (1 <= shape_num <= 5):
                print "  Number ", shape_num ," is OK."
                break
            else:
                print
                print "  The number you entered must be from 1 to 5 only."
        except:
            print
            print "  Only numbers allowed - Please try again"
    return shape_num



#=========#=========#=========#=========#=========#=========#=========#
def main():
    how_many()
#=========#=========#=========#=========#=========#=========#=========#
if __name__ == "__main__":
    main()

#=========#=========#=========#=========#=========#=========#=========#

---

这是主菜单的内容

---

#!/usr/bin/python

## my_menu.py

import sub_menu as s_m
import draw_shape as d_s

#=========#=========#=========#=========#=========#=========#=========#
def main():
    while True:
        print
        print "  Draw a Shape"
        print "  ============"
        print
        print "  1 - Draw a triangle"
        print "  2 - Draw a square"
        print "  3 - Draw a rectangle"
        print "  4 - Draw a pentagon"
        print "  5 - Draw a hexagon"
        print "  6 - Draw an octagon"
        print "  7 - Draw a circle"
        print
        print "  X - Exit"
        print

        choice = raw_input('  Enter your choice: ')

        if (choice == 'x') or (choice == 'X'):
            break

        elif (choice >= "1" and choice <= "7"):
            my_shape_num = s_m.how_many()
            # draw in the middle of screen if == 1
            if (my_shape_num == 1):
                d_s.start_point(0, 0)
            else:
                d_s.start_point()
            #
            if choice == '1': 
                d_s.draw_triangle(my_shape_num) 
            elif choice == '2': 
                d_s.draw_square(my_shape_num) 
            elif choice == '3':             
                d_s.draw_rectangle(my_shape_num) 
            elif choice == '4':             
                d_s.draw_pentagon(my_shape_num) 
            elif choice == '5':             
                d_s.draw_hexagon(my_shape_num) 
            elif choice == '6':             
                d_s.draw_octagon(my_shape_num) 
            elif choice == '7': 
                d_s.draw_circle(my_shape_num)

            d_s.t.end_fill() # shape fill color --draw_shape.py-- def start_point

        else:
            print
            print '  Try again'
            print


#=========#=========#=========#=========#=========#=========#=========#

if __name__ == "__main__":
    main()

#=========#=========#=========#=========#=========#=========#=========#

---

这是drawshape的内容

---

#!/usr/bin/python

## draw_shape.py

import turtle as t

#=========#=========#=========#=========#
def start_point(x=-240, y=0):
    # Added 23 dec 11 baris
    t.color("black", "red")
    t.shapesize(outline=8)
    t.begin_fill()
    #
    t.penup() 
    t.setpos(x, y) 
    t.pendown()

def spaces_after(x=120):
    t.penup() 
    t.forward(x)
    t.pendown()

#=========#=========#=========#=========#
def draw_triangle(num=1):
    for a in range(num): 
        for a in range(3): 
            t.forward(80) 
            t.left(120)
        spaces_after()
#=========#=========#=========#=========#
def draw_square(num=1):
    for a in range(num): 
        for a in range(4): 
            t.forward(80) 
            t.left(90)
        spaces_after()
#=========#=========#=========#=========#        
def draw_rectangle(num=1):
    for a in range(num):
        for a in range(2): 
            t.forward(80) 
            t.left(90)
            t.forward(40)
            t.left(90)
        spaces_after()
#=========#=========#=========#=========#
def draw_pentagon(num=1):
    for a in range(num): 
        for a in range(5): 
            t.forward(50) 
            t.left(72)
        spaces_after()
#=========#=========#=========#=========#        
def draw_hexagon(num=1):
    for a in range(num): 
        for a in range(6): 
            t.forward(50) 
            t.left(60)
        spaces_after()
#=========#=========#=========#=========#        
def draw_octagon(num=1):
    for a in range(num): 
        for a in range(8): 
            t.forward(40) 
            t.left(45)
        spaces_after()
#=========#=========#=========#=========#
def draw_circle(num=1):
    for a in range(num): 
        t . circle(50)
        spaces_after()
#=========#=========#=========#=========#=========#=========#=========#
def main():
    start_point()

    draw_triangle()
    draw_square()
    draw_rectangle()
    draw_pentagon()
    draw_hexagon()
    draw_octagon()
    draw_circle()

    t.end_fill()

#=========#=========#=========#=========#=========#=========#=========#
if __name__ == "__main__":
    main()

#=========#=========#=========#=========#=========#=========#=========#

Answer 1

你只需要两行代码就能做到这一点。

在 sub_menu.py 文件里，你需要像这样添加对 "0" 的处理：

...
try:
            shape_num = int(shape_num)
            if ( shape_num == 0):
                return None
            if (1 <= shape_num <= 5):
                print "  Number ", shape_num ," is OK."
                break
            else:
                print
                print "  The number you entered must be from 1 to 5 only."
        except:
 ....

然后在 main.py 文件里，你需要这样做：

my_shape_num = s_m.how_many()
            if ( my_shape_num is None):
                continue

这样就可以重新显示主菜单了。

如果你想的话，还可以加一句提示（按 0 取消）。