2d数组Python问题，如果范围，elifs，一个不按预期工作

Question

我有下面的程序，用户输入一个数字an放在矩阵的位置上。

我试图，为了教学目的，解决它只使用选择(目前)。

您会注意到，它适用于所有数字，但0除外。最后一个elif是小于1 -e.g的数字。0。代码告诉它将X放置在0,0位置，但它将其放置在7中。

怎么回事？https://trinket.io/python/987e8c46d7

注意，我只添加了最后一个elif，因为第一个也应该处理小于7的数字的elif不起作用。我如何使用相同的结构来处理这个问题。

然后，我想在关注if语句的教学基础上，研究重复或不需要复杂的地方，以表明它可以进一步简化，以获得更优雅的代码。

def matrix():
  print("---The Matrix---")
  #create a 1d array of 7 stars
  matrix1=[
  ["*","*","*","*","*","*","*"],
  ["*","*","*","*","*","*","*"],
  ["*","*","*","*","*","*","*"],
  ["*","*","*","*","*","*","*"],
  ["*","*","*","*","*","*","*"],
  ["*","*","*","*","*","*","*"],
  ["*","*","*","*","*","*","*"]
  ]
  #user enters a number
  number=int(input("Enter number:"))
  #you are always finding the remainder on each row to place the X
  remainder=number%7
  
  #an 'X' is placed in the position of the number
  #remainder-1 because we start at index 0
  
  if number<=7:
    matrix1[0][remainder-1]="X"
  elif number>7 and number<15:
    matrix1[1][remainder-1]="X"
  elif number>14 and number<22:
    matrix1[2][remainder-1]="X"
  elif number>21 and number<29:
    matrix1[3][remainder-1]="X"
  elif number>28 and number<36:
    matrix1[4][remainder-1]="X"
  elif number>35 and number<43:
    matrix1[5][remainder-1]="X"
  elif number>42 and number<50:
    matrix1[6][remainder-1]="X"
  elif number<1:
    matrix[0][0]=="X"


  #the updated matrix is printed.
  print(matrix1)
matrix()

Answer 1

您的el-if语句应该如下所示。在您的实现中，当用户输入0作为输入号时，代码会变成if number <=7语句。因此，if number<1:语句应该放在第一位。

...

  if number<1:
    matrix1[0][0]="X"
  elif number<=7:
    matrix1[0][remainder-1]="X"
  elif number>7 and number<15:
    matrix1[1][remainder-1]="X"
  elif number>14 and number<22:
    matrix1[2][remainder-1]="X"
  elif number>21 and number<29:
    matrix1[3][remainder-1]="X"
  elif number>28 and number<36:
    matrix1[4][remainder-1]="X"
  elif number>35 and number<43:
    matrix1[5][remainder-1]="X"
  elif number>42 and number<50:
    matrix1[6][remainder-1]="X"

...

Answer 2

如果是number < 1，那么number <= 7，那么if语句中的第一个条件将在到达number < 1检查之前应用。在这种情况下，剩下的是0，因此它将索引matrix1[0][-1]，这是该行中的最后一项。您应该将number < 1检查移到if语句的开头，以解决这个问题。另外，我认为这段代码有一个错误，因为您访问的是matrix而不是matrix1，您使用的是==运算符而不是赋值。

  if number < 1:
    matrix1[0][0] = "X"
  elif number<=7:
    matrix1[0][remainder-1]="X"
  elif number>7 and number<15:
    matrix1[1][remainder-1]="X"
  elif number>14 and number<22:
    matrix1[2][remainder-1]="X"
  elif number>21 and number<29:
    matrix1[3][remainder-1]="X"
  elif number>28 and number<36:
    matrix1[4][remainder-1]="X"
  elif number>35 and number<43:
    matrix1[5][remainder-1]="X"
  elif number>42 and number<50:
    matrix1[6][remainder-1]="X"

Answer 3

只需对第一个索引使用int除法就可以做到这一点，而不是让一堆if语句单独将每个范围映射到相同的结果：

def matrix():
    print("---The Matrix---")
    # create a 2d array of 7x7 stars
    matrix1 = [["*" for _ in range(7)] for _ in range(7)]

    number = int(input("Enter number: "))
    matrix1[number // 7][number % 7] = "X"

    # print the matrix
    print('\n'.join(''.join(row) for row in matrix1))


matrix()

---The Matrix---
Enter number: 0
X******
*******
*******
*******
*******
*******
*******

---The Matrix---
Enter number: 48
*******
*******
*******
*******
*******
*******
******X

如果您希望用户输入的数字从1-49变为0-48，只需在用户输入后从number中减去1即可。您可以使用min和max“剪辑”1以下和49以上的输入。

number = int(input("Enter number: ")) - 1
number = max(number, 0)
number = min(number, 48)