在python的2D数组中交换两个字符？

Question

So, I'm brand new to programming, and this is frustrating me! What I want to do is be able to import a 4x8 text file, and turn the text into a 2D list so that I can swap two characters. For example, if the imported text file looks like this:

OOOOOOOO
OOOXOOOO
OOOOOOOO
OOOOOOOO

then I would like to be able to change the position of the X (the row/column location) when user input is entered, such that an O will get put in its place to preserve formatting. So, for exapmle, the program will prompt the user for their input and if the user enters "up," then the X will move one space up.

OOOXOOOO
OOOOOOOO
OOOOOOOO
OOOOOOOO

I want it to repeatedly prompt for a new move after each time one is made, and display the new grid each time (so you can see the X in its new position each time you enter a movement).

This is all I have so far. I know I need to first find the X, but I really don't know how to. I'm stuck here. Any help is appreciated.

#Global variables for the movements
UP = 8
DOWN = 2
RIGHT = 6
LEFT = 4

#Dimensions of grid
ROWS = 4
COLUMNS = 8

def start():        
    filename = input("Enter the name of the Start Positions file: ")
    textFile = open(filename)
    aMaze = [line.strip() for line in textFile]
    for r in range(ROWS):
        for c in range(COLUMNS):
            print(aMaze[r][c], end="")
        print()

def moveType():
    while (True):
        try:
            move = input("ENTER YOUR MOVE: ") 
        except ValueError:
            print("unimportant error message")
            continue
        if ((int(move)) in (DOWN, LEFT, RIGHT, UP)):
            playerMove(move)
            continue
        else:
            print("unimportant error message")
            continue            
    return(move)

def playerMove(move):
    move = (int(move))
    if (move == DOWN):
        #need help here
    elif (move == UP):
        #and here
    elif (move == LEFT):
        #don't know what i'm doing
    elif (move == RIGHT):
        #also here

start()
moveType()

Answer 1

This is a perfect opportunity to learn about abstraction. To solve your problem, think about the sub problems you could solve (with functions) that would make your final problem easier.

In your specific instance, wouldn't it be easier to write a program to find the Cartesian coordinates of where X is? With an (x,y) coordinate, you could then make a function to turn that coordinate (likely stored as a tuple) into a 2d array where that coordinate is an X an everything else is a zero.

Hint 1:

x =0
y =0
for row in numrows:
    for col in numcols:
        if array[row][col] == X
            y = row
            x = col

Hint 2:

for row in numrows:
    for col in numcols:
        if col is x and row is y:
            place X
        else:
            place O

Note: if this were an application where you wanted to eek out every bit of performance, you certainly would not need to iterate through your array every time to find X. You could (and should) opt to store the location of X and then use two accesses into your array to flip X's and O's. But seeing as this is likely one of your first problems you are solving this is of course not a concern.

Hope this helps! Good luck starting to code!