在多个文件中使用但在函数调用后未更改的全局变量（Python）

Question

I declared a global variable in my settings.py module:

def init():
    global grid
    grid = [[0,0,0,0,0,0,1,4,3],
            [9,0,0,0,0,0,0,0,0],
            [0,0,2,0,4,5,0,8,0],
            [0,0,0,0,0,3,0,1,0],
            [0,6,0,4,9,1,0,5,0],
            [0,4,0,6,0,0,0,0,0],
            [0,8,0,7,5,0,4,0,0],
            [0,0,0,0,0,0,0,0,8],
            [2,1,5,0,0,0,0,0,0]]

I have an other module called run.py, that contains a function that should modify grid:

import numpy
import settings

def solve():

    for x in range(9):
        for y in range(9):
            if settings.grid[x][y] == 0:
                for number in range(1,10):
                    if possible(x,y,number): #function described in this file, not usefull here
                        settings.grid[x][y] = number
                        solve()
                        settings.grid[x][y] = 0
                return

    print("Solved sudoku in solve():\n{}\n".format(numpy.matrix(settings.grid))) #2nd output

In my main.py, I first initialize settings.grid by calling settings.init(). After, I basically print the grid variable from settings.py, then call run.solve() to modify it (it is working since the 2nd output will replace the 0s) and then reprint settings.grid to see if the variable was changed accordingly to the 2nd output:

import numpy
import settings
import run


settings.init()

print("Inserted sudoku:\n{}\n".format(numpy.matrix(settings.grid)))

run.solve()

print("Solved sudoku:\n{}\n".format(numpy.matrix(settings.grid)))

My problem is, the 3rd output is not taking the same value of settings.grid like the 2nd one like if run.solve() was not even called!

This is the ouputs i get:

1st output 
Inserted sudoku:
[[0 0 0 0 0 0 1 4 3]
 [9 0 0 0 0 0 0 0 0]
 [0 0 2 0 4 5 0 8 0]
 [0 0 0 0 0 3 0 1 0]
 [0 6 0 4 9 1 0 5 0]
 [0 4 0 6 0 0 0 0 0]
 [0 8 0 7 5 0 4 0 0]
 [0 0 0 0 0 0 0 0 8]
 [2 1 5 0 0 0 0 0 0]]

2nd output
Solved sudoku in solve():
[[6 5 8 9 2 7 1 4 3]
 [9 3 4 1 6 8 2 7 5]
 [1 7 2 3 4 5 9 8 6]
 [8 2 9 5 7 3 6 1 4]
 [7 6 3 4 9 1 8 5 2]
 [5 4 1 6 8 2 3 9 7]
 [3 8 6 7 5 9 4 2 1]
 [4 9 7 2 1 6 5 3 8]
 [2 1 5 8 3 4 7 6 9]]

3rd output
Solved sudoku:
[[0 0 0 0 0 0 1 4 3]
 [9 0 0 0 0 0 0 0 0]
 [0 0 2 0 4 5 0 8 0]
 [0 0 0 0 0 3 0 1 0]
 [0 6 0 4 9 1 0 5 0]
 [0 4 0 6 0 0 0 0 0]
 [0 8 0 7 5 0 4 0 0]
 [0 0 0 0 0 0 0 0 8]
 [2 1 5 0 0 0 0 0 0]]

Do you have any idea of how I can get the 3rd output like the 2nd one? In other words, do you know how I can change settings.grid value to be changed in my main.py after a run.solve() call?

Thanks in advance

Answer 1

I reproduced as possible your situation and I think I get the desired result. This is what I did

settings.py

def init():
    global grid
    grid = [0, 0]

Updated to have some recursion

run.py

import settings

def solve(i = 1):
    if i >= 0:
        settings.grid[i] = i + 1
        solve(i - 1)

main.py

import settings
import run

settings.init()

print(settings.grid)

run.solve()

print(settings.grid)

And the new output is:

[0, 0]
[1, 2]
>>> 

Note : In your code after the recursive call you're setting the position back to 0 , it may not be your issue but I think you have to check that out.

settings.grid[x][y] = number
solve()
settings.grid[x][y] = 0 # <==== Right here