对if/elif语句有问题吗

Question

对于代码中的“dog”部分，它工作得很好，并且做了它应该做的事情。但是，如果您在开始时输入“Cat”作为输入问题，它仍然继续执行代码的dog部分。在

即使我在代码中写过，如果问题的答案=“Cat”或“Cat”，那么它应该执行这个部分，而不是Dog部分。在

import time
import sys

animal=input("What animal do you want to calculate the age of? - Possible choices: Cat/Dog")

if animal=="Dog"or"dog":
    age=int(input("How old is your Dog?"))
    if age==1:
        print("Calculating the age of the Dog...")
        time.sleep(1)
        print("The age of the animal is: 11")
    elif age==2:
        print("Calculating the age of the Dog...")
        time.sleep(1)
        print("The age of the animal is: 11")
    else:
        age=age-2
        print("Calculating the age of the Dog...")
        time.sleep(1)
        agecalculation=age*4+22
        print("The age of the animal is:",agecalculation)
        time.sleep(2)
        print("End of program.")
        time.sleep(2)
        sys.exit()

elif animal=="Cat"or"cat":
    age=int(input("How old is your Cat?"))
    if age==1:
        print("Calculating the age of the Cat...")
        time.sleep(1)
        print("The age of the animal is: 15")
    elif age==2:
        print("Calculating the age of the Cat...")
        time.sleep(1)
        print("The age of the animal is: 25")
    else:
        age=age-2
        print("Calculating the age of the Cat...")
        time.sleep(1)
        agecalculation=age*4+25
        print("The age of the animal is:",agecalculation)
        time.sleep(2)
        print("End of program.")
        time.sleep(2)
        sys.exit()
else:
    print("That is not an animal, or isn't on the list specified")
    animal=input("What animal do you want to calculate the age of? - Possible choices: Cat/Dog")             

Answer 1

您需要按如下方式编辑代码：

import time
import sys

animal=input("What animal do you want to calculate the age of? - Possible choices: Cat/Dog")

if animal=="Dog"or animal=="dog":
    age=int(input("How old is your Dog?"))
    if age==1:
        print("Calculating the age of the Dog...")
        time.sleep(1)
        print("The age of the animal is: 11")
    elif age==2:
        print("Calculating the age of the Dog...")
        time.sleep(1)
        print("The age of the animal is: 11")
    else:
        age=age-2
        print("Calculating the age of the Dog...")
        time.sleep(1)
        agecalculation=age*4+22
        print("The age of the animal is:",agecalculation)
        time.sleep(2)
        print("End of program.")
        time.sleep(2)
        sys.exit()

elif animal=="Cat"or animal == "cat":
    age=int(input("How old is your Cat?"))
    if age==1:
        print("Calculating the age of the Cat...")
        time.sleep(1)
        print("The age of the animal is: 15")
    elif age==2:
        print("Calculating the age of the Cat...")
        time.sleep(1)
        print("The age of the animal is: 25")
    else:
        age=age-2
        print("Calculating the age of the Cat...")
        time.sleep(1)
        agecalculation=age*4+25
        print("The age of the animal is:",agecalculation)
        time.sleep(2)
        print("End of program.")
        time.sleep(2)
        sys.exit()
else:
    print("That is not an animal, or isn't on the list specified")
    animal=input("What animal do you want to calculate the age of? - Possible choices: Cat/Dog")             

当您执行if animal == "Dog" or "dog"时，它将计算if animal == "Dog"，if{}。您可以使用animal.lower() == "dog"，或者使用上面编辑过的代码。在

Answer 2

在python中，所有非空字符串都被计算为true，如下所示：

if "something":
    print("True")
else
    print("False")

将始终打印True

因此，您需要设置if like：

^{pr2}$

Answer 3

以下if测试的结果始终为true：

if animal=="Dog" or "dog":

上面的工作方式就好像有括号一样：

^{pr2}$

在Python规则下，or的第二部分将始终求值为True：非空字符串的布尔值为True。在

以下是三种可行的选择：

if animal=="Dog" or animal == "dog":

if animal in ("Dog", "dog"):

if animal.lower() =="dog":

更多：这些问题可以在python方便的交互式命令提示符上轻松测试。例如，观察"Dog"和""的布尔值：

>>> bool("Dog"), bool("")
(True, False)

下面是合并声明：

>>> bool('Cat' == 'Dog' or 'dog')
True