当我输入整数时，为什么这显示不是整数？

Why does this show as not an integer when I input an integer? (Python)

本问题已经有最佳答案，请猛点这里访问。

如你所知，我是一个相当新手的Python编码人员。目前，我只是做了一些小的测试程序，在尝试任何大的程序之前，要确保所有的缩进和任何正确的操作。因此，我试图确保如果输入不是整数，那么程序输出一条消息，表示必须输入整数。但是，对于我所拥有的当前代码(我认为应该是正确的)，无论答案是什么，都会输出"请输入一个整数"消息。我做错了什么？代码如下：

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a = input("What is your age?")
b = 7
c = ((a-2) * 4) +25
if a == int:
print"Your age in a small dog's years is:", ((a-2) * 4)+28
print"Your age in a medium sized dog's years is:", ((a-2) * 6)+27
print"Your age in a big dog's years is:", ((a-2) * 9)+22
print"Your age in cat years is:", c
print"Your age in guinea pig years is:", a * 15
print"Your age in hamster years is:", a * 20
print"Your age in pig years is:", ((a-1) * 4)+18
print"Your age in goldfish years is:", ((a-1) * 8)+188
print"Your age in cow years is:", ((a-1) * 4)+14
print"Your age in horse years is:", a * 3
print"Your age in goat years is:", ((a-1) * 6)+18
print"Your age in rabbit years is:", ((a-1) * 8)+20
print"Your age in chinchilla years is:", ((a-1) * 7)+17
elif a != int:
print"You must enter an integer!"

否则它会起作用，只是这条小小的两头线，似乎会毁了它。谢谢。