检查索引是否在二维列表中 [Python]

Question

I have to write a function (def) that checks if index that I write is inside the 2d list. If it is it must return True, otherwise it must return False.

def height(board):
    height=0
    for x in board:
        height+=1
    return height

def width(board):
    wid=len(board[0])
    return wid

def on_board(board, x, y):
    check=False
    x1 = int(x)
    y1 = int(y)
    for x,y in board:
        if x1 > height(board) or y1 > width(board):
            check=False
    else:
        check=True
    return check

List looks something like this:

board = [["V1", "V1"],
         ["V2", "V2"],
         ["V3", "V3"]]

Answer 1

The easiest way is with try..except..else , which will attempt to access that spot on the board. If it works, it's a valid location, and the else block will be entered. If not, it isn't, and the except block will be entered. As a bonus, you can also check for whether x and y are valid integers. Any failure here will produce False .

def on_board(board, x, y):
    try:
        board[int(x)][int(y)]
    except (ValueError, IndexError):
        return False
    else:
        return True

Also, the height of the board is simply def height(board): return len(board) . But if you only have height() and width() for the purpose of on_board() , then you don't need height() and width() at all.

As determined in chat , the testing suite which is checking your program is using 0-indexed rows and columns like we are, but the first value is the column (like an x-coordinate on a graph) and the second value is the row. It also doesn't accept indices of -1 for the user to indicate the last row/column. Finally, it's testing the function with integers already, so there's no need to cast with int() .

def on_board(board, x, y):
    return x in range(len(board[0])) and y in range(len(board))

This checks whether x is between 0 (inclusive) and the number of columns in a row (non-inclusive), and whether y is between 0 (inclusive) and the number of rows in the board (non-inclusive). It then returns the boolean value for whether both of those conditions are true.

Answer 2

You can use your two methods as written, then your on_board method can be simply checking those

def height(board):
    return len(board)

def width(board):
    return len(board[0])

def on_board(board, x, y):
    return x < width(board) and y < height(board)

For example

>>> board = [["V1", "V1"],
             ["V2", "V2"],
             ["V3", "V3"]]
>>> on_board(board, 1, 0)
True
>>> on_board(board, 3, 4)
False