Split list into smaller lists (split in half)

python

list-slicing

generators

performance-optimization

Chop a list into two using integer division and list slicing:

lst = [1, 2, 3, 4, 5, 6]
half = len(lst) // 2  # Split at midway, no need to play "eeny, meeny, miny, moe"
halves = lst[:half], lst[half:]

Access it like halves[0] for the first half and halves[1] for the second half. Yes, you don't need a chainsaw for slicing lists!

No panic for odd-sized lists, Python slicing slays it by including the extra element in the second sublist. Python got your back!

More than half: smaller equally distributed slices

When you want to share your pizza with more friends, distribute equally into 3 slices each:

lst = [1, 2, 3, 4, 5, 6, 7, 8, 9]
slice_size = 3
slices = [lst[i:i + slice_size] for i in range(0, len(lst), slice_size)]

To pick every second slice of pizza from the box or every third, Python has a step feature in slicing:

step2 = lst[::2]  # Picks every 2nd slice, starting from the first
step3 = lst[::3]  # Picks every 3rd slice, starting from the first

A reusable function can handle different party sizes:

def pizza_slices(pizza, slice_size):
    return [pizza[i:i + slice_size] for i in range(0, len(pizza), slice_size)]

Now, just say pizza_slices(lst, 3) to get sublists of 3 elements each. The party gets simplified!

While slicing is your friend, here are some friendly reminders:

Index Errors: Slicing doesn't throw tantrums if you go out of bounds. But, expect an empty slice in return! Pay attention to your indices.
Sharing is caring: Slicing shares a shallow copy, keeping a reference to the same objects for nested objects within the list.
Big party considerations: Slicing a large pizza (or list) could result in slower service (or performance). Generators can help serve large parties (or datasets).

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