请问这个计算区域的代码有什么问题？ （Python）的

Question

您好 我是python的新手。我不知道为什么这段代码不起作用：

def area_finder_rectangle (height,width):
    area = height*width
    print("The area of your polygon is %.2f" % area)


def area_finder_triangle (height,width):
    area = (height*width)*0.5
    print("The area of your polygon is %.2f" % area)


while True:

    print ("Choose the polygon that you want to calculate the area from.")
    print ("Polygons supported: rectangle, triangle")
    value = str(input("Your polygon is a: "))
    print ("Be sure to include decimals even if you are going to input an integer")

    if value == "rectangle" or "Rectangle":

        heightt = float(input("Enter height: "))
        widthh = float(input("Enter width: "))
        area_finder_rectangle (height = heightt,width = widthh)

    elif value == "triangle" or "Triangle":
        heightt = float(input("Enter height: "))
        widthh = float(input("Enter width: "))
        area_finder_triangle (height = heightt,width = widthh)

    print ("")

当您选择矩形时很好，但是当您选择三角形时，会发生这种情况：

    >>>
    Choose the polygon that you want to calculate the area from.
    Polygons supported: rectangle, triangle
    Your polygon is a: triangle
    Be sure to include decimals even if you are going to input an integer
    Enter height: 10
    Enter width: 10
    The area of your polygon is 100.00

Answer 1

if value == "rectangle" or "Rectangle":

不是你的想法。它会将value与表达式"rectangle" or "Rectangle"的完整结果进行比较，该结果将始终评估为True。它应该是这样的：

if value == "rectangle" or value == "Rectangle":

但更好的选择是

if value.lower() == "rectangle":

甚至更好，直接在输入处转换为小写。

value = str(input("Your polygon is a: ")).lower()

旁注：

如果要将值与多个值进行比较，可以这样做：

if value in ["rectangle", "Rectangle", "RECTANGLE"]:

但在这种情况下，这不是一个最佳选择。在比较之前只需转换为小写。

这是完整的代码：

def area_finder_rectangle (height,width):
    area = height*width
    print("The area of your polygon is %.2f" % area)


def area_finder_triangle (height,width):
    area = (height*width)*0.5
    print("The area of your polygon is %.2f" % area)


while True:

    print ("Choose the polygon that you want to calculate the area from.")
    print ("Polygons supported: rectangle, triangle")
    value = str(input("Your polygon is a: ")).lower()
    print ("Be sure to include decimals even if you are going to input an integer")

    if value == "rectangle":

        heightt = float(input("Enter height: "))
        widthh = float(input("Enter width: "))
        area_finder_rectangle (height = heightt,width = widthh)

    elif value == "triangle":
        heightt = float(input("Enter height: "))
        widthh = float(input("Enter width: "))
        area_finder_triangle (height = heightt,width = widthh)

    print ("")

一个测试人员：

[klutt@klutt-sandbox tmp]# python3 polygon.py
Choose the polygon that you want to calculate the area from.
Polygons supported: rectangle, triangle
Your polygon is a: rectangle
Be sure to include decimals even if you are going to input an integer
Enter height: 10.0
Enter width: 10.0
The area of your polygon is 100.00

Choose the polygon that you want to calculate the area from.
Polygons supported: rectangle, triangle
Your polygon is a: triangle
Be sure to include decimals even if you are going to input an integer
Enter height: 10.0
Enter width: 10.0
The area of your polygon is 50.00

您应该考虑的一件事是，在这种情况下，您可以更容易地发现问题，就是在无效输入的情况下始终添加else。

    if value == "rectangle":
        <do something>    
    elif value == "triangle":
        <do something>
    else:
        print("Unknown polygon")

Answer 2

您的分支if value == "rectangle" or "Rectangle:"将始终被拍摄，您将始终计算一个矩形。如果你放入括号，为什么这样做更有意义。

    if (value == "rectangle") or ("Rectangle"):

如果value是'triangle'，则第一部分的计算结果为False，但or-condition的第二部分计算结果为True，因为在Python中，布尔上下文中的非空字符串被视为True

要获得您想要的效果，您需要说

    if (value == "rectangle") or (value == "Rectangle"):