Python int / str檢查

Question

我有一個家庭作業，並且我已經完成了最少的作業，但是在進行作業時，我對如何使我的程序變得更好感興趣。 代碼的重點是繪制用戶定義的形狀，並在輸入無效輸入時提供反饋。 我想繼續做下去，所以如果用戶輸入一個str作為高度/寬度或坐標之一，它將給出一個錯誤，但是我無法弄清楚該怎么做。 這是一個入門課程，因此，如果您要牢記，我們只是進入while循環，而對於if / else / etc，我們已經進行了循環。

這是我目前擁有的代碼：

def draw_user_shape(pen):
    shape = input("Please enter a shape: ")
    while shape != "square" and shape != "rectangle" and shape != "triangle":
        shape = input("Invalid shape, please enter either square, rectangle, or triangle: ")
    if shape == "square":
        h = input("Please enter a height: ")
        while h != int or int(h) < 1:
            h = input("That is an invalid height, please enter an positive integer: ")
        h = int(h)
        c = input("Please enter a color: ")
        while c != str and str(c) != "red" and str(c) != "green" and str(c) != "blue":
            c = input("That is an invalid color, please enter either red, blue, or green: ")
        c = str(c)
        x = input("Please enter an x-coordinate: ")
        while x != int and int(x) == 1:
            x = input("That is an invalid x-coordinate, please enter an integer: ")
        x = int(x)
        y = input("Please enter a y-coordinate: ")
        while y != int and int(y) == int:
            y = input("That is an invalid y-coordinate, please enter an integer: ")
        y = int(y)
        pen.fillcolor(c)
        pen.up()
        pen.goto(x,y)
        pen.down()
        pen.begin_fill()
        pen.goto(x,y+h)
        pen.goto(x+h,y+h)
        pen.goto(x+h,y)
        pen.goto(x,y)
        pen.end_fill()
        pen.up()
    elif shape == "rectangle":
        h = input("Please enter a height: ")
        while h != int and int(h) < 1:
            h = input("That is an invalid height, please enter an positive integer: ")
        h = int(h)
        w = input("Please enter a width: ")
        while w != int and int(w) < 1:
            w = input("That is an invalid height, please enter an positive integer: ")
        w = int(w)
        c = input("Please enter a color: ")
        while c != str and str(c) != "red" and str(c) != "green" and str(c) != "blue":
            c = input("That is an invalid color, please enter either red, blue, or green: ")
        c = str(c)
        x = input("Please enter an x-coordinate: ")
        while x != int and int(x) == 1:
            x = input("That is an invalid x-coordinate, please enter an integer: ")
        x = int(x)
        y = input("Please enter a y-coordinate: ")
        while y != int and int(y) == int:
            y = input("That is an invalid y-coordinate, please enter an integer: ")
        y = int(y)
        pen.fillcolor(c)
        pen.up()
        pen.goto(x, y) 
        pen.down()
        pen.begin_fill()
        pen.goto(x,y+h)
        pen.goto(x+w,y+h)
        pen.goto(x+w,y)
        pen.goto(x,y)
        pen.end_fill()
        pen.up()
    elif shape == "triangle":
        h = input("Please enter a height: ")
        while h != int and int(h) < 1:
            h = input("That is an invalid height, please enter an positive integer: ")
        h = int(h)
        w = input("Please enter a width: ")
        while w != int and int(w) < 1:
            w = input("That is an invalid height, please enter an positive integer: ")
        w = int(w)
        c = input("Please enter a color: ")
        while c != str and str(c) != "red" and str(c) != "green" and str(c) != "blue":
            c = input("That is an invalid color, please enter either red, blue, or green: ")
        c = str(c)
        x = input("Please enter an x-coordinate: ")
        while x != int and int(x) == 1:
            x = input("That is an invalid x-coordinate, please enter an integer: ")
        x = int(x)
        y = input("Please enter a y-coordinate: ")
        while y != int and int(y) == int:
            y = input("That is an invalid y-coordinate, please enter an integer: ")
        y = int(y)
        pen.fillcolor(c)
        pen.up()
        pen.goto(x,y)
        pen.down()
        pen.begin_fill()
        pen.goto(x+w/2,y+h)
        pen.goto(x+w,y)
        pen.goto(x,y)
        pen.end_fill()
        pen.up()

def main():
    import turtle
    pen = turtle.Turtle()
    draw_user_shape(pen)

main()

Answer 1

在這種情況下，您想使用異常處理。 基本上，這個想法是接受輸入並嘗試將其轉換為int 。 如果失敗，則會引發ValueError 。 否則，您將取回轉換后的值。 請記住，輸入將始終以str形式提供給您，因此您不能簡單地測試它是否為int 。 假設您使用的是Python 3，則可以執行以下操作來不斷詢問，直到輸入正確的值為止：

# keep asking for input until we get the right one
while True:
    myInput = input('give me a number: ')
    try:
        myValue = int(myInput)
        # if we reach this point, that means we got our number
        break # this will jump out of the loop
    except ValueError:
        # if we reach this point, that means the input was bad
        print('invalid input')

Answer 2

我建議使用

not h.isdigit()

檢查字符串h是否不包含整數。 它不適用於浮點數，因為它真正要檢查的是每個數字是否在0-9范圍內，以及. 將不會（正確）識別為數字。

例如線

while h != int or int(h) < 1:

會成為

while not h.isdigit() or int(h) < 1:

順便說一句，我假設您使用的是Python 3.x，否則您的代碼將無法工作，因為input在Python 2.x中的工作方式有所不同。 在Python 3.x中，它應始終返回字符串，因此沒有任何理由檢查返回的對象是否為字符串。

Answer 3

>>> isinstance('a', int)
False
>>> isinstance(2, int)
True

Answer 4

使用.isdigit()或.isalnum() 進行檢查 ， .isalnum()您的偏好

1. 例

    str_num= 'aaaa7777' str_num.isalnum() # true str_num.isdigit() # false 

2. 例

    str_num= 'aaaa 7777' # Note that has spaces str_num.isalnum() # false str_num.isdigit() # false 

3. 例

    str_num= '7777' str_num.isalnum() # True str_num.isdigit() # True