How do i make a grid in python?

问题

This is my code

width = int(input("How wide?"))
height = int(input("How high?"))
grid = []
row = []
bak = "."
for i in range(width):
    row.append(bak)
for i in range(height):
    grid.append(row)
while True:
    for i in range(len(grid)):
        print(grid[i])

It's not working and i don't know why. This is what i get when i put 5 width and 5 height:

['.', '.', '.', '.', '.']
['.', '.', '.', '.', '.']
['.', '.', '.', '.', '.']
['.', '.', '.', '.', '.']
['.', '.', '.', '.', '.']

That's fine and all but when i change the bottom left dot by using this: grid[0][0] = "a". This happens:

['a', '.', '.', '.', '.']
['a', '.', '.', '.', '.']
['a', '.', '.', '.', '.']
['a', '.', '.', '.', '.']
['a', '.', '.', '.', '.']

It thinks the "row" list is a tag when it's clearly coded not to be Please help me on how to fix this problem

回答1:

for i in range(height):
    grid.append(row)

This for loop appends the same row list to the grid list (actually it appends 5 different references to the same list).

Instead, you should append a new, different list:

for i in range(height):
    grid.append([])

Verify by viewing the memory addresses of the inner lists in these 2 examples:

grid = []
row = []
for i in range(5):
    grid.append(row)
for li in grid:
    print(id(li))
# 92532104
# 92532104
# 92532104
# 92532104
# 92532104

compared to

grid = []
for i in range(5):
    grid.append([])
for li in grid:
    print(id(li))

# 80801224
# 80801160
# 80669704
# 80381192
# 80380488

回答2:

Use list()

gridline = []
for i in range(5):
    gridline.append("")
grid = []
for i in range(5):
    grid.append(list(gridline))

来源：https://stackoverflow.com/questions/41910947/how-do-i-make-a-grid-in-python

标签

python

grid