Update and rename split_list.md to chunk_into_n.md

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Isabelle Viktoria Maciohsek
2020-10-12 22:11:30 +03:00
committed by GitHub
parent 9a3809c000
commit d0d234ebed
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---
title: chunk_into_n
tags: list,intermediate
---
Chunks a list into `n` smaller lists.
- Use `math.ceil()` and `len()` to get the size of each chunk.
- Use `list()` and `range()` to create a new list of size `n`.
- Use `map()` to map each element of the new list to a chunk the length of `size`.
- If the original list can't be split evenly, the final chunk will contain the remaining elements.
```py
from math import ceil
def chunk_into_n(lst, n):
size = ceil(len(lst) / n)
return list(
map(lambda x: lst[x * size:x * size + size],
list(range(0, n)))
)
```
```py
chunk_into_n([1, 2, 3, 4, 5, 6, 7], 4)) # [[1, 2], [3, 4], [5, 6], [7]]
```

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---
title: split_list
tags: list,divmod,intermediate
---
Splits a long list into "`parts`" number of smaller lists, which are as close as possible to each other in length.
- Check if `parts` is larger than `len(lst)` in order to not split the list into more parts than there are elements.
- The `max(len(lst), 1)` check will handle zero length lists, but `parts < 1` will yield bad results.
- `k = len(lst)//n` -> an integer specifying the number of elements in each shorter list (i.e. the quotient).
- `m = len(lst)%n` -> if `len(lst)/n` does not equal a whole number, this equals how many "extra" elements there are (i.e. the remainder).
- In order to get `n` short lists, every loop iteration goes to `i * k` and then take the next `k` elements.
- If `m > 0`, then the early iterations will have one extra element in their list until `i > m` (no extra elements left).
- Return a meta-list containing all these shorter lists.
```py
def split_list(lst: list, parts: int) -> list:
n = min(parts, max(len(lst), 1))
k, m = divmod(len(lst), n)
return [lst[i * k + min(i, m):(i + 1) * k + min(i + 1, m)] for i in range(n)]
```
```py
l = [1, 2, 3, 4, 5, 6]
split_list(l, 2) # [[1, 2, 3], [4, 5, 6]]
split_list(l, 4) # [[1, 2], [3, 4], [5], [6]]
split_list(l, 9) # [[1], [2], [3], [4], [5], [6]]
```