🔒 List errors

[thorn jolt]

this is driving me crazy. i dont see what im doing wrong

[wheat kernel]

@thorn jolt

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[thorn jolt]

positions = [[]] * int((WID*HEI)/256+160) #length of 4160
    for mov in particles:
        t = mov.update(WID,HEI) # t is an int (and can only possibly be an int)
        positions[t].append(mov) # shouldn't this only modify one sublist??
        #This line for some reason adds "mov" to every sublist in "positions"
        #When it should only add to one sublist (denoted by "t")

[dense kettle]

You have created a list where each item contains the same object. Updating one object updates all of them.

You should use a list comprehension with range() or look at numpy

positions = [[] for _ in range(length)]

[thorn jolt]

got it

[dense kettle]

for numpy, you just wrap what you currently have in np.array([[0] * HEI] * WID)

[thorn jolt]

this worked, thx

[dense kettle]

!e ```py
import numpy as np
ar = np.array([[0] * 10] * 10)

ar[0,0] = 1
print(ar)

[wheat kernel]

@dense kettle :white_check_mark: Your 3.12 eval job has completed with return code 0.

001 | [[1 0 0 0 0 0 0 0 0 0]
002 |  [0 0 0 0 0 0 0 0 0 0]
003 |  [0 0 0 0 0 0 0 0 0 0]
004 |  [0 0 0 0 0 0 0 0 0 0]
005 |  [0 0 0 0 0 0 0 0 0 0]
006 |  [0 0 0 0 0 0 0 0 0 0]
007 |  [0 0 0 0 0 0 0 0 0 0]
008 |  [0 0 0 0 0 0 0 0 0 0]
009 |  [0 0 0 0 0 0 0 0 0 0]
010 |  [0 0 0 0 0 0 0 0 0 0]]

[quasi sapphire]

the expression
int((WID*HEI)/256+160)
can be simplified to
WID*HEI // 256 + 160
the // operator is a blessing, don't leave integer space unless strictly necessary

[wheat kernel]

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