如何打印上一行/多行？

Question

key = int(input("Choose a Christmas Gift from 1 to 5!"))

 if type(key) != type(0):

  print("Please enter a number.")

  exit()

 if not (1 <= key <= 5):

  print(key,"is an invalid number.")

  exit()

if key == 1:

 print("1 Partridge in a Pear Tree.")

elif key == 2:

 print("2 Turtle Doves.")

elif key == 3:

 print("3 French Hens.")

elif key == 4:

 print("4 Calling Birds.")

elif key == 5:

 print("5 Golden Rings.")

我已经走了这么远（我对此很陌生，我做了我在课堂上看到的），但是当你输入一个数字时，我不知道如何打印前几行。

假设我输入 3。

输出应该是：

3 french hens.

2 turtle doves

1 partridge in a pear tree.

它应该对所有有效数字都这样做。

编辑：我将 eval 更改为 int。

任何建议都有帮助！谢谢你。

Answer 1

反转您的测试，使它们基于>=、not==和不使用elif（这使得通过的第一个测试阻止任何其他测试执行），只是简单的if. 现在，每个通过的测试都会按顺序打印。if key >= 5:&nbsp; &nbsp; print("5 Golden Rings.")if key >= 4:&nbsp; &nbsp; print("4 Calling Birds.")if key >= 3:&nbsp; &nbsp; print("3 French Hens.")if key >= 2:&nbsp; &nbsp; print("2 Turtle Doves.")if key >= 1:&nbsp; &nbsp; print("1 Partridge in a Pear Tree.")

Answer 2

我所做的是反转它们，以便它们从最大到最小打印，如果大于该数字，则将 == 设置为 >= 进行打印。from sys import exitkey = int(input("Choose a Christmas Gift from 1 to 5!"))if type(key) != type(0):&nbsp; &nbsp; print("Please enter a number.")&nbsp; &nbsp; exit()if not (1 <= key <= 5):&nbsp; &nbsp; print(key,"is an invalid number.")&nbsp; &nbsp; exit()if key >= 5:&nbsp; &nbsp; print("5 Golden Rings.")if key >= 4:&nbsp; &nbsp; print("4 Calling Birds.")if key >= 3:&nbsp; &nbsp; print("3 French Hens.")if key >= 2:&nbsp; &nbsp; print("2 Turtle Doves.")if key >= 1:&nbsp; &nbsp; print("1 Partridge in a Pear Tree.")但是，如果您想扩展它，请执行以下操作：from sys import exit&nbsp; &nbsp; key = int(input("Choose a Christmas Gift from 1 to 5!"))&nbsp; &nbsp; if type(key) != type(0):&nbsp; &nbsp; &nbsp; &nbsp; print("Please enter a number.")&nbsp; &nbsp; &nbsp; &nbsp; exit()&nbsp; &nbsp; if not (1 <= key <= 5):&nbsp; &nbsp; &nbsp; &nbsp; print(key,"is an invalid number.")&nbsp; &nbsp; &nbsp; &nbsp; exit()gifts = ["1 partridge in a pair tree","2 turtle doves","etc..","etc..","etc.."]printer = [print (val) for ind,val in enumerate (gifts) if ind >=key]打印机通过使用列表理解来工作，这与所说的相同for ind,val in enumerate(gifts):&nbsp; &nbsp;if ind >= key:&nbsp; &nbsp; &nbsp; print(val)