b = a[:] in python

In Python, you can use slicing to create a copy of a list. The b = a[:] statement creates a new list b that contains all the elements of list a but is a separate object, meaning that if you modify b, a won't change, and vice versa.

Here is an example:

main.py
a = [1, 2, 3, 4]
b = a[:] # create a copy of list a
b[0] = 10 # modify b
print(a) # prints [1, 2, 3, 4]
print(b) # prints [10, 2, 3, 4]
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In this example, we assign a a list of four integers. Then, we create a copy of a and assign it to b using the slice notation. We modify the first element of b, and then print out both a and b. Note that a is unchanged, while b has been modified.

Using slicing to create a copy of a list is a very common idiomatic Python technique.