虽然循环不会停止循环

Question

我对 python 或一般编码有点陌生，我在我的 while 循环中遇到了问题。我想指出，while 循环仅在变量“loop”= True 时才有效

loop = True #Makes the asking sequence work


def loop_again(): #Makes the program ask if you want to continue
    loop_again = str(input("Do you want to do this again? Yes or No: "))
    if loop_again == "Yes":
        loop = True
    elif loop_again == "No":
        loop = False
    else:
        print("Please answer yes or no: ")
        loop_again

当我在程序询问我是否要再次执行此操作时写“否”时，它仍然循环序列，即使当我键入“否”时变量“循环”应该是假的，这应该是停止循环。

完整代码（代码底部的while循环）：

#Solving for the area in a shape automatically

import math

loop = True #Makes the asking sequence work


def loop_again(): #Makes the program ask if you want to continue
    loop_again = str(input("Do you want to do this again? Yes or No: "))
    if loop_again == "Yes":
        loop = True
    elif loop_again == "No":
        loop = False
    else:
        print("Please answer yes or no: ")
        loop_again



def sqr_area(): #Asking sequence for the area of the square
    if choose == "Square":
        a = float(input("Input the length of the side here: "))
        print(a ** 2)
        loop_again()

def rec_area(): #Asking sequence for the area of the rectangle
    if choose == "Rectangle":
        a = float(input("Input the length of the long sides here: "))
        b = float(input("Input the length of the short sides here: "))
        print(a * b)
        loop_again()

def tri_area(): #Asking sequence for the area of the triangle
    a = float(input("Input the length of the side: "))
    b = float(input("Input the length of the height: "))
    print((a * b) / 2)
    loop_again()

def cir_area(): #Asking sequence for the area of the circle
    r = float(input("Length of the radius: "))
    print((r ** 2) * math.pi)
    loop_again()

while loop == True: #While loop, asking sequence
    choose = str(input("Input what shape that you want to figure out the area of here: "))
    if choose == "Square":
        sqr_area()
    elif choose == "Rectangle":
        rec_area()
    elif choose == "Triangle":
        tri_area()
    elif choose == "Circle":
        cir_area()
    else:
        print("Invalid shape, Input one of these shapes: Square, Rectangle, Triangle, Circle")
        choose

提前致谢！

Answer 1

当您应该使用循环时不要使用递归，loop_again 应该返回一个值，而不是全局设置 loop。

import math


# Returns true once the input is Yes or false once the input is No
def loop_again():
    while True:
        response = str(input("Do you want to do this again? Yes or No: "))
        if response == "Yes":
            return True
        elif response == "No":
            return False
        else:
            print("Please answer yes or no: ")

loop_again 应该在相关的*_area 函数返回之后被调用，而不是在每个函数内部。这些功能不需要知道或关心 关于choose的值；仅在打算调用它们时才调用它们。

# Print the area of a square
def sqr_area():
    a = float(input("Input the length of the side here: "))
    print(a ** 2)


# Print the area of a rectangle
def rec_area():
    a = float(input("Input the length of the long sides here: "))
    b = float(input("Input the length of the short sides here: "))
    print(a * b)


# Print the area of a triangle
def tri_area():
    a = float(input("Input the length of the side: "))
    b = float(input("Input the length of the height: "))
    print((a * b) / 2)


# Print the area of a circle
def cir_area():
    r = float(input("Length of the radius: "))
    print((r ** 2) * math.pi)

最后的循环可以无限期地运行，直到loop_again 返回True。

# Loop until the user chooses to not run again
while True:
    choose = input("Input what shape that you want to figure out the area of here: ")
    if choose == "Square":
        sqr_area()
    elif choose == "Rectangle":
        rec_area()
    elif choose == "Triangle":
        tri_area()
    elif choose == "Circle":
        cir_area()
    else:
        print("Invalid shape, Input one of these shapes: Square, Rectangle, Triangle, Circle")
        continue

    if loop_again():
        break

Answer 2

在loop_again() 函数中你必须在开头添加这个：

global loop

否则，该变量被视为本地，不会对外部范围内的其他 loop 变量产生任何影响。

Answer 3

这是一个上下文变量问题。您在loop_again() 中拥有的loop 变量和while 循环中的变量是不同的。 在 python 中，函数内部的每个变量都是局部变量，除非它是一个参数，或者如果您在 main 和函数内部使用 global variable。

所以让它成为全局的或者在函数内部传递和返回

#Solving for the area in a shape automatically

import math
global loop 
loop = True #Makes the asking sequence work


def loop_again(): #Makes the program ask if you want to continue
    global loop 
    loop_again = str(input("Do you want to do this again? Yes or No: "))
    if loop_again == "Yes":
        loop = True
    elif loop_again == "No":
        loop = False
    else:
        print("Please answer yes or no: ")
        loop_again



def sqr_area(): #Asking sequence for the area of the square
    if choose == "Square":
        a = float(input("Input the length of the side here: "))
        print(a ** 2)
        loop_again()

def rec_area(): #Asking sequence for the area of the rectangle
    if choose == "Rectangle":
        a = float(input("Input the length of the long sides here: "))
        b = float(input("Input the length of the short sides here: "))
        print(a * b)
        loop_again()

def tri_area(): #Asking sequence for the area of the triangle
    a = float(input("Input the length of the side: "))
    b = float(input("Input the length of the height: "))
    print((a * b) / 2)
    loop_again()

def cir_area(): #Asking sequence for the area of the circle
    r = float(input("Length of the radius: "))
    print((r ** 2) * math.pi)
    loop_again()

while loop == True: #While loop, asking sequence
    global loop 
    choose = str(input("Input what shape that you want to figure out the area of here: "))
    if choose == "Square":
        sqr_area()
    elif choose == "Rectangle":
        rec_area()
    elif choose == "Triangle":
        tri_area()
    elif choose == "Circle":
        cir_area()
    else:
        print("Invalid shape, Input one of these shapes: Square, Rectangle, Triangle, Circle")
        choose

你需要在每个函数中说明循环是全局的，否则python你将它解释为一个局部变量。

另一种方法是：

import math
loop = True #Makes the asking sequence work


def loop_again(loop ): #Makes the program ask if you want to continue
    loop_again = str(input("Do you want to do this again? Yes or No: "))
    if loop_again == "Yes":
        loop = True
    elif loop_again == "No":
        loop = False
    else:
        print("Please answer yes or no: ")
        loop_again
    return loop



def sqr_area(loop): #Asking sequence for the area of the square
    if choose == "Square":
        a = float(input("Input the length of the side here: "))
        print(a ** 2)
        loop = loop_again()
    return loop

def rec_area(loop): #Asking sequence for the area of the rectangle
    if choose == "Rectangle":
        a = float(input("Input the length of the long sides here: "))
        b = float(input("Input the length of the short sides here: "))
        print(a * b)
        loop = loop_again(loop)
    return loop


def tri_area(loop): #Asking sequence for the area of the triangle
    a = float(input("Input the length of the side: "))
    b = float(input("Input the length of the height: "))
    print((a * b) / 2)
    loop = loop_again()

def cir_area(loop): #Asking sequence for the area of the circle
    r = float(input("Length of the radius: "))
    print((r ** 2) * math.pi)
    loop = loop_again()

while loop == True: #While loop, asking sequence
    choose = str(input("Input what shape that you want to figure out the area of here: "))
    if choose == "Square":
        loop = sqr_area(loop )
    elif choose == "Rectangle":
        loop = rec_area(loop )
    elif choose == "Triangle":
        loop = tri_area(loop )
    elif choose == "Circle":
        loop = cir_area(loop )
    else:
        print("Invalid shape, Input one of these shapes: Square, Rectangle, Triangle, Circle")
        choose```