python - 输入矩阵值后无法跳出 while 循环

Question

我正在编写一个简单的程序来创建矩阵并对它们执行某些操作。我之前用 python 2.7 编写了这个程序，并且运行良好。但是，它似乎不适用于 python 3.7。系统会提示用户输入矩阵的行和列，并输入两者的值( float )。但每当用户输入“quit”时，它都会要求用户再次输入行和列。如果有人能告诉我为什么它没有跳出 while 循环“while value != quit1:”，那将不胜感激。

还有一个 ValueError (cannot conversion string to float: 'quit')

每当我在程序后输入“quit”时，因为在输入值时该值被转换为 float 。我注释掉了 value = float(value) 行，以测试它是否会跳出 while 循环。当该行取消注释时，它会返回 ValueError。谢谢

def main():

    print("Welcome to the matrix program!")
    print("Enter the number of dimensions: ")
    m = int(input("Enter number of rows: "))
    n = int(input("Enter number of columns: "))
    matrix = []
    for i in range(m):
        matrix.append([])
        for j in range(n):
            matrix[i].append(0)
    print(matrix)
    value = 0
    quit1 = str("quit").upper
    while value != quit1:
        row_loc = int(input("Enter a row location: "))
        col_loc = int(input("Enter a column location: "))
        value = input("Enter a value for the matrix of QUIT to stop: ")
        if value != quit1:
            value = float(value)
            matrix[row_loc-1][col_loc-1] = value
        else:
            value = quit1

    print(matrix)
    choices = "What would you like to do? \n(1) APPLY \n(2) TRANSPOSE \n(3) PRINT \n(4) QUIT"
    print(choices)
    choice = int(input("Choice: "))

Answer 1

看来您的问题由两部分组成。出现 ValueError 是因为 value = float("QUIT") 正在 if 语句中运行。然而，它首先将其放入 if 语句的原因是 quit1 在 upper 函数调用中缺少 ()，并且您可能应该标准化输入。像这样的东西应该有效:

def main():

    print("Welcome to the matrix program!")
    print("Enter the number of dimensions: ")
    m = int(input("Enter number of rows: "))
    n = int(input("Enter number of columns: "))
    matrix = []
    for i in range(m):
        matrix.append([])
        for j in range(n):
            matrix[i].append(0)
    print(matrix)
    value = 0
    quit1 = str("quit").upper()
    while value != quit1:
        row_loc = int(input("Enter a row location: "))
        col_loc = int(input("Enter a column location: "))
        value = input("Enter a value for the matrix of QUIT to stop: ")
        if value.upper() != quit1:
            value = float(value)
            matrix[row_loc-1][col_loc-1] = value
        else:
            value = quit1

    print(matrix)
    choices = "What would you like to do? \n(1) APPLY \n(2) TRANSPOSE \n(3) PRINT \n(4) QUIT"
    print(choices)
    choice = int(input("Choice: "))

您还可以通过修改 while 语句中的相同内容并删除 else 来进一步简化逻辑