Fastest way to initialize a List in Python? (comparison of 3 options)

Fastest way to initialize a List in Python? (comparison of 3 options)

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#Python

[GN]

Using [[0] * n] * n] creates a list of a list at the same point in memory, i.e. myList[0] is myList[1]

[calum.macleod]

I love how Python optimises some things, in ways that we might not have expected.

I really like your channel, I've only been programming Python for a year but you are helping to set important ideas in my head that were not obvious before.

Thank you.

[alexpaciniat]

Mutables can create tricky situations, whether as multiplicative elements in lists, where it is effectively the same object in memory and repeated, or when used as default argument in a function, where if modified it will effectively change the default value of the next call to that function.

[GyroCannon]

The optimization is (assuming that the underlying structure is an array list) probably due to the code knowing how big to make the list. The other ways probably default to 10 or something and double in size each time it gets too big

[pattmehta]

+1 for the disclaimer to not use this technique in a nested list. Very useful for scenarios where latency is critical

[shivanshmathur]

#Fastest as it uses numpy, which is a low level language
import numpy as np
n = 5 # Replace 5 with your desired size
Listofzeros = np.zeros(n)
MyList = list(Listofzeros)
print(MyList)

[pzkpfw]

Sir, Loeber!! Thank you for the content on your YT channel.

[ytusr-korg]

I've recognized it when creating a 2d list:
board1 = [[0]*3]*3
# would be different from
board2 = [[0 for j in range(3)] for i in range(3)]

# let's take a closer look
# when I want to update the cell data of the board[row][column]

>>> board1[0][0] = 1
>>> board1
[[1, 0, 0], [1, 0, 0], [1, 0, 0]]
>>> board2[0][0] = 1
>>> board2
[[1, 0, 0], [0, 0, 0], [0, 0, 0]]

# it's dangerous. Be careful with this python behavior:)
# Using list-comprehension is the correct way.

[bekhzodravshanov]

You cant multiply nested list.
You have to use loop for creating it

[amrosamier]

Thank you..what IDE are you using please

[MrJonas]

Why do you write the "_" in "for _ in list"? You usually use something like "for element in list", don't you?