🔒 Numpy array

[heady breach]

is it okay to create a big numpy array inside a loop or would it be better to create it before the loop starts

[charred peak]

@heady breach

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[bold moth]

one would need more information to answer that. but you should pretty much never pre-allocate an array and iteratively populate it

# this is wrong
arr = np.zeros((5, 3))
for i in range(5):
   for j in range(3):
     arr[i, j] = some_func(i, j)

[heady breach]

how to do that code properly

[bold moth]

what are you trying to do

!code

[charred peak]

Formatting code on Discord

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print('Hello world!')
```

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[bold moth]

please do not post screenshots of text

[charred peak]

Hey @heady breach!

It looks like you're trying to paste code into this channel.

Discord has support for Markdown, which allows you to post code with full syntax highlighting. Please use these whenever you paste code, as this helps improve the legibility and makes it easier for us to help you.

To do this, use the following method:
```py
print('Hello, world!')
```

This will result in the following:

print('Hello, world!')```
You can **edit your original message** to correct your code block.

[bold moth]

please read this

[heady breach]

def modify_Tm(x, y, m):
    L_old = L
    if m == 0:
        flag1 = find_nearest_node(x-1)
        flag2 = Tm(flag1, y, m)
        flag3 = Tm_eq(flag1, y)
    elif m == 1:
        flag1 = find_nearest_node(y+1)
        flag2 = Tm(x, flag1, m)
        flag3 = Tm_eq(x, flag1)
    elif m == 2:
        flag1 = find_nearest_node(x+1)
        flag2 = Tm(flag1, y, m)
        flag3 = Tm_eq(flag1, y)
    elif m == 3:
        flag1 = find_nearest_node(y - 1)
        flag2 = Tm(x, flag1, m)
        flag3 = Tm_eq(x, flag1)
    L[x][y][m] = flag2 - W * (flag2 - flag3)

[bold moth]

thank you

[heady breach]

i need the copy of L array

to have acces on previous step

[bold moth]

assignment never copies data in Python, so L_old = L will not create a copy

you have to do L_old = L.copy() for that

[heady breach]

i mean

i need to overwrite it

without overwriting original

wait

other way around

i need to owerwrite original

without owerwriting old

[bold moth]

L_old and L refer to the exact same object, so any changes made to L will appear in L_old, because they are the same thing.

[heady breach]

oh i see

so if i just assign it gonna work as link

[bold moth]

assignments just assign names to things. they don't create or copy data.

another thing is that L[x][y][m] should be L[x, y, m]

arrays are one object, no matter how many dimensions they have. whereas nested lists are multiple objects. @heady breach

[heady breach]

OKAY THANKS

[bold moth]

YOU ARE WELCOME

[charred peak]

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