[英]Create and initialize 5x5 grid for Battleships
So I just completed a section of CodeAcademy Battleship problem, and have submitted a correct answer but am having trouble understanding why it is correct. 所以我刚刚完成了CodeAcademy Battleship问题的一部分,并提交了正确的答案,但我很难理解为什么它是正确的。
The idea is to build a 5x5 grid as a board, filled with "O's". 我们的想法是建立一个5x5网格作为板,填充“O”。 The correct code I used was: 我使用的正确代码是:
board = []
board_size=5
for i in range(board_size):
board.append(["O"] *5)
However I'm confused as to why this didn't create 25 "O's" in one single row as I never specified to iterate to a separate row. 但是我很困惑为什么这不会在一行中创建25个“O”,因为我从未指定迭代到单独的行。 I tried 我试过了
for i in range(board_size):
board[i].append(["O"] *5)
but this gave me the error: IndexError: list index out of range
. 但这给了我错误: IndexError: list index out of range
。 Can anyone explain why the first one is correct and not the second one? 任何人都可以解释为什么第一个是正确的而不是第二个?
["O"]*5
This creates a list of size 5, filled with "O": ["O", "O", "O", "O", "O"]
这将创建一个大小为5的列表,其中填充“O”: ["O", "O", "O", "O", "O"]
board.append(["O"] *5)
This appends (adds to the end of the list) the above list to board[]. 这将上面的列表添加(添加到列表的末尾)到board []。 Doing this 5 times in a loop creates a list filled with 5 of the above lists. 在循环中执行此操作5次会创建一个列表,其中包含上述5个列表。
[["O", "O", "O", "O", "O"],
["O", "O", "O", "O", "O"],
["O", "O", "O", "O", "O"],
["O", "O", "O", "O", "O"],
["O", "O", "O", "O", "O"]]
Your code did not work, because lists are not initialized with a size in python, it just starts as an empty container []
. 你的代码不起作用,因为列表没有用python中的大小初始化,它只是作为一个空容器[]
。 To make yours work, you could have done: 为了让你的工作,你可以做到:
board = [[],[],[],[],[]]
and in your loop: 在你的循环中:
board[i] = ["O"]*5
Python lists start out empty: Python列表从空开始:
board = [] # empty list
Unlike some programming languages, you do not specify or initialise the bounds of the array, so if you try to access by index: 与某些编程语言不同,您不指定或初始化数组的边界,因此如果您尝试通过索引访问:
board[0]
you will get an IndexError
; 你会得到一个IndexError
; there is not yet any index 0
. 还没有任何索引0
。
In the first version, on each trip through the for
loop, you append
(add to the end of the list) a new list containing five "O"
s. 在第一个版本中,在每次通过for
循环的行程中,您append
(添加到列表的末尾)一个包含五个"O"
的新列表 。 If you want the board
list to contain 25 "O"
s, you should use extend
instead: 如果您希望board
列表包含25 "O"
,则应使用extend
代替:
for i in range(board_size):
board.extend(["O"] *5)
Code should look like this. 代码应如下所示。 board = [] for i in range(0, 5): board.append(["O"]*5) print(board)
I think the problem is simple: when you run your code, your array is empty! 我认为问题很简单:当你运行代码时,你的数组是空的!
You could issue a 你可以发一个
board = [[], [], [], [], []]
to initialize it as a nested, five places array. 将其初始化为嵌套的五位数组。
You could also use a dict to simulate a indefinitely nested array: 您还可以使用dict来模拟无限嵌套的数组:
board=defaultdict(lambda:defaultdict(lambda:[]))
This is because each time you run board.append(["O"] *5)
you create a new list (because of the square brackets used inside the append statement). 这是因为每次运行board.append(["O"] *5)
都会创建一个新列表(因为append语句中使用了方括号)。
If you would have used board.append("O" *5)
instead the you would get a single list with five elements like: 如果您使用board.append("O" *5)
代替,您将得到一个包含五个元素的列表:
['OOOOO', 'OOOOO', 'OOOOO', 'OOOOO', 'OOOOO'] ['OOOOO','OOOOO','OOOOO','OOOOO','OOOOO']
The *5 multiplies the string. * 5乘以字符串。 if you just run from an interactive prompt 'O' * 5
you get: 如果你只是从交互式提示'O' * 5
你会得到:
'OOOOO' 'OOOOO'
However, if you run ['O'] * 5
it multiplies the text within the list and you get a list with five elements. 但是,如果你运行['O'] * 5
它会将列表中的文本相乘,你会得到一个包含五个元素的列表。
['O', 'O', 'O', 'O', 'O'] ['O','O','O','O','O']
You appended five lists, each having 5 elements. 您附加了五个列表,每个列表包含5个元素。
board = []
board_size=5
for i in range(board_size):
board.append(["O"] *5)
In this code board
starts as an empty list. 在此代码board
中以空列表开头。 ["O"] * 5
will create a list that is equal to ["O", "O", "O", "O", "O"]
. ["O"] * 5
将创建一个等于["O", "O", "O", "O", "O"]
。 It will then be appended to the list board
. 然后它将附加到列表board
。 This will happen 5 times in this example since board_size == 5
. 由于board_size == 5
在此示例中将发生这种情况5次。
for i in range(board_size):
board[i].append(["O"] *5)
This wouldn't work unless the item at index i
was a list since append()
is a method of the list
class. 除非索引i
的项是列表,否则这将无效,因为append()
是list
类的方法。 If you wanted to insert something at i
you would use the list method insert()
如果你想在i
处插入一些东西,你会使用list方法insert()
First step in codeacademy codeacademy的第一步
board = []
for i in range(5):
board.append(["O"]*5)
print board
Second step in codeacademy codeacademy的第二步
board = []
def print_board(board):
for x in range(5):
board= (["O"] * 5)
print board
return board
print_board(board)
third step in codeacademy codeacademy的第三步
board = []
def print_board(board):
for x in range(5):
board= (["O"] * 5)
print " ".join(board)
return board
print_board(board)
4th Step 第四步
from random import randint
board = []
for x in range(0, 5):
board.append(["O"] * 5)
def print_board(board):
for row in board:
board = " ".join(row)
return board
def random_row(board):
return randint(0, len(board) - 1)
def random_col(board):
return randint(0, len(board) - 1)
print print_board(board)
print random_row(board)
print random_col(board)
5th step of buttleship on codeacademy 在codeacademy上的第五步buttleship
from random import randint
board = []
for x in range(0,5):
board.append(["O"] * 5)
def print_board(board):
for row in board:
print " ".join(row)
def random_row(board):
return randint(0, len(board) - 1)
def random_col(board):
return randint(0, len(board[0]) - 1)
ship_row = random_row(board)
ship_col = random_col(board)
guess_row = int(raw_input("Guess Row: "))
guess_col = int(raw_input("Guess Col: "))
from random import randint
board = [] for x in range(5): board.append(["O"] * 5) board = [] for x in range(5):board.append([“O”] * 5)
def print_board(board): for row in board: print " ".join(row) def print_board(board):for board in board:print“”。join(row)
print "Let's play Battleship!" 打印“让我们玩战舰!” print_board(board) print_board(板)
def random_row(board): return randint(0, len(board) - 1) def random_row(board):return randint(0,len(board) - 1)
def random_col(board): return randint(0, len(board[0]) - 1) def random_col(board):return randint(0,len(board [0]) - 1)
ship_row = random_row(board) ship_col = random_col(board) print ship_row print ship_col ship_row = random_row(board)ship_col = random_col(board)print ship_row print ship_col
turns=0 win = 0 for turn in range(4): if turn <= 5: guess_row = int(raw_input("Guess Row:")) guess_col = int(raw_input("Guess Col:")) turn = 0 win = 0 for turn in range(4):if turn <= 5:guess_row = int(raw_input(“Guess Row:”))guess_col = int(raw_input(“Guess Col:”))
if guess_row == ship_row and guess_col == ship_col:
print "Congratulations! You sunk my battleship!"
win +=1
if win == 2:
break
else:
turns +=1
if (guess_row < 0 or guess_row > 4) or (guess_col < 0 or guess_col > 4):
print "Oops, that's not even in the ocean."
elif(board[guess_row][guess_col] == "X"):
print "You guessed that one already."
else:
print "You missed my battleship!"
board[guess_row][guess_col] = "X"
print (turn + 1)
print_board(board)
elif turns == 3:
print "Game Over"
else:
print "Max Turn try is over Try Again"
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