Apa tipe-tipe berguna sing diberikan dening modul collections?

Question

Accepted Answer

Modul **`collections`** nyediakan tipe-tipe kontainer khusus sing ngembangake list/dict/tuple bawaan kanthi alternatif sing nenggeri lan asring luwih efisien kanggo pola-pola umum. Ngerti babagan iki ngidini sampeyan nulis kode sing luwih resik lan cepet.

## defaultdict — dicts kanthi nilai default otomatis

```python
from collections import defaultdict

# ❌ without it — must check/initialize keys manually
groups = {}
for item in items:
    if item.category not in groups:
        groups[item.category] = []
    groups[item.category].append(item)

# ✅ defaultdict auto-creates the default for missing keys
groups = defaultdict(list)        # missing key → a new empty list
for item in items:
    groups[item.category].append(item)   # no existence check needed
```

`defaultdict(list)` (utawa `int`, `set`, etc.) nyediakake default kanggo kunci sing ilang apa wae — ngilangake pola cek-lan-inisialisasi sing ngrepotake. Apik banget kanggo pengelompokan lan pitung-pitungan.

## Counter — pitung-pitungan kemunculan

```python
from collections import Counter

c = Counter("mississippi")         # Counter({'i': 4, 's': 4, 'p': 2, 'm': 1})
c.most_common(2)                    # [('i', 4), ('s', 4)] — top 2
c["x"]                              # 0 — missing keys return 0, no error

Counter(["a", "b", "a", "c", "a"])  # count list items → {'a': 3, 'b': 1, 'c': 1}
```

`Counter` nggawe pitung-pitungan frekuensi dadi gampang — pitung tembung, suara, kemunculan — kanthi metode sing nenggeri kayata `most_common`.

## deque — append/pop cepet SA LORO ujung

```python
from collections import deque

q = deque([1, 2, 3])
q.append(4)          # add to the right
q.appendleft(0)      # add to the LEFT — O(1) (a list's insert(0) is O(n)!)
q.popleft()          # remove from the left — O(1)
q = deque(maxlen=3)  # bounded — auto-drops old items (sliding window)
```

`deque` yaiku antrian kanthi loro ujung kanthi O(1) append/pop sa loro ujung — ideal kanggo antrian, stack, lan jendela geser (list polos yaiku O(n) kanggo operasi ngarep).

## namedtuple — rekaman ringan, sinebut

```python
from collections import namedtuple

Point = namedtuple("Point", ["x", "y"])
p = Point(3, 4)
p.x, p.y          # 3, 4 — access by NAME (clearer than p[0], p[1])
p                 # Point(x=3, y=4) — readable
```

`namedtuple` menehi tuples kolom sinebut — luwih kaandalan tinimbang akses indeks, immutable, hemat memori. (Kode modern asring nganggo `@dataclass` tinimbang para rekaman sing bisa ganti.)

## OrderedDict / ChainMap (kurang umum saiki)

```text
OrderedDict → ordered dict (less needed since regular dicts keep order in 3.7+)
ChainMap    → search multiple dicts as one (e.g. layered config/defaults)
```

## Napa iki Penting

Modul `collections` nyediakake alat sing pas kanggo pola-pola umum, nyebabake kode sing luwih resik lan asring luwih efisien. `defaultdict` lan `Counter` nyederhanakake pengelompokan lan pitung-pitungan kanthi drastis (nggantike logika manual sing cukup sulit); `deque` menehi operasi loro-ujung O(1) ing mana list bakal alon; `namedtuple` nggawe rekaman ringan sing kaandalake.

Majekaken iki tinimbang nggawa pola sing padha karo dict/list polos yaiku tandha kode Python sing idiomatis lan produktif — luwih dienggo ing kode nyata kanggo pangolahan data, algoritma, lan API sing resik.