退出菜单的最简单方法

Question

我完成了所有的作业，但是我忘了在子菜单下放一个取消选项。我不想改变我所有的文件，这花了2天的时间。在sub_menu.py

上添加取消并返回主菜单选项最简单的方法是什么?

这是sub_menu.py

#!/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()
#=========#=========#=========#=========#=========#=========#=========#

---

这是主要的

---

#!/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()
#=========#=========#=========#=========#=========#=========#=========#

---

这是一个drawshape

---

#!/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

可以用两行代码完成。在sub_menu.py中，你应该像这样添加"0"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:
 ....

，在main.py中你应该做

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

这将重新打印主菜单。

如果需要，还应该添加一条指令(按0取消)。