x = eval(input('请输入一个x')) if x < 0: y = 0 elif 0 <= x < 5: y = x elif 5 <= x < 10: y = 3 * x - 5 elif 10 <= x < 20: y = 0.5 * x - 2 else: y = 0 print(y)
3x--->3*x 0.5x---->0.5*x