fix groupby should yield tuples of key Seq_T (#67)

README.md

@@ -67,7 +67,10 @@ Other Python projects have had similar ideas:
 #### Philosophy
 * Make it work: Concise syntax borrowed from Scala, Rust etc.
 * Make it right: Fully typed, no exceptions
-* Make it fast: Concurrency through `.pmap`, potentially caching in the future
+* Make it fast: 
+    * Concurrency through `.pmap`
+    * (Future): Caching
+    * (Future): Refactor operations to use generators
 * Keep it simple: No dependencies
 
 #### API design

functionalpy/_sequence.py

@@ -4,7 +4,6 @@
     Callable,
     Iterable,
     Iterator,
-    Mapping,
     Sequence,
 )
 from functools import reduce
@@ -61,20 +60,24 @@ def reduce(self, func: Callable[[_T, _T], _T]) -> _T:
 
     def groupby(
         self, func: Callable[[_T], str]
-    ) -> "Mapping[str, Sequence[_T]]":
-        mapping: defaultdict[str, list[_T]] = defaultdict(list)
+    ) -> "Seq[tuple[str, list[_T]]]":
+        groups_with_values: defaultdict[str, list[_T]] = defaultdict(
+            list
+        )
 
-        for item in self._seq:
-            mapping[func(item)].append(item)
+        for value in self._seq:
+            value_key = func(value)
+            groups_with_values[value_key].append(value)
 
-        return dict(mapping)
+        tuples = list(groups_with_values.items())
+        return Seq(tuples)
 
     def flatten(self) -> "Seq[_T]":
         values: list[_T] = []
 
         for i in self._seq:
             if isinstance(i, Sequence) and not isinstance(i, str):
-                values.extend(i)
+                values.extend(i)  # type: ignore
             else:
                 values.append(i)
 

functionalpy/_sequence.pyi

@@ -6,16 +6,12 @@ from collections.abc import (
     Callable,
     Iterable,
     Iterator,
-    Mapping,
-    Sequence,
 )
 from typing import Generic, TypeVar, overload
 
 _T = TypeVar("_T")
 _S = TypeVar("_S")
 
-# TODO: Attempt generic type alias for container types
-
 class Seq(Generic[_T]):
     def __init__(self, iterable: Iterable[_T]) -> None: ...
     def count(self) -> int: ...
@@ -31,7 +27,7 @@ class Seq(Generic[_T]):
     def reduce(self, func: Callable[[_T, _T], _T]) -> _T: ...
     def groupby(
         self, func: Callable[[_T], str]
-    ) -> Mapping[str, Sequence[_T]]: ...
+    ) -> Seq[tuple[str, list[_T]]]: ...
     @overload
     def flatten(self: Seq[list[_S]]) -> Seq[_S]: ...
     @overload

functionalpy/benchmark/query_1/iterators_q1.py

@@ -105,7 +105,7 @@ def main_iterator(data: Sequence[Item]) -> Sequence[CategorySummary]:
 
     summaries = [
         summarise_category(group, rows=values)
-        for group, values in mapping.items()
+        for group, values in mapping.to_iter()
     ]
 
     return summaries

functionalpy/test_sequence.py

@@ -1,4 +1,4 @@
-from collections.abc import Mapping, Sequence
+from collections.abc import Sequence
 from typing import Literal
 
 from functionalpy._sequence import Seq
@@ -58,11 +58,13 @@ def is_even(num: int) -> str:
             return "even"
         return "odd"
 
-    grouped: Mapping[str, Sequence[int]] = sequence.groupby(is_even)
-    assert grouped == {
-        "odd": [1, 3],
-        "even": [2, 4],
-    }
+    grouped: list[tuple[str, list[int]]] = sequence.groupby(
+        is_even
+    ).to_list()
+    assert grouped == [
+        ("odd", [1, 3]),
+        ("even", [2, 4]),
+    ]
 
 
 def test_flatten():