From a1f4605d8bd969f531365c1b746bcb094de54966 Mon Sep 17 00:00:00 2001
From: monoid <qaswedfr55@gmail.com>
Date: Wed, 23 Feb 2022 20:24:35 +0900
Subject: [PATCH] feat: groupby_index

---
 groupby_index.py      | 36 ++++++++++++++++++++++++++++++++++++
 groupby_index.test.py |  9 +++++++++
 2 files changed, 45 insertions(+)
 create mode 100644 groupby_index.py
 create mode 100644 groupby_index.test.py

diff --git a/groupby_index.py b/groupby_index.py
new file mode 100644
index 0000000..0c37a6d
--- /dev/null
+++ b/groupby_index.py
@@ -0,0 +1,36 @@
+import itertools
+from typing import Tuple, TypeVar, Iterable
+
+T = TypeVar('T')
+
+def groupby_index(iter: Iterable[T],n:int) -> Iterable[Iterable[T]]:
+    """group list by index
+
+    Args:
+        iter (Iterable[T]): iterator to group by index
+        n (int): The size of groups
+
+    Returns:
+        Iterable[Iterable[T]]: iterable object to group by index
+
+    >>> [*map(lambda x:[*x],groupby_index([1,2,3,4],2))]
+    [[1, 2], [3, 4]]
+    """
+    def keyfunc(x: Tuple[int,T]) -> int:
+        k, _ = x
+        return (k // n)
+    def mapper(x: Tuple[int, Tuple[int, T]]):
+        _, v = x
+        return map(lambda y: y[1],v)
+    g = itertools.groupby(enumerate(iter), keyfunc)
+    return map(mapper,g)
+
+if __name__ == "__main__":
+    test_list = [*range(20,-10,-1)]
+    for g in groupby_index(test_list,4):
+        print([*g])
+    print("===")
+    print([*map(lambda x:[*x],groupby_index([1,2,3,4],2))])
+    for g in groupby_index([1,2,3,4],2):
+        print([*g])
+    
\ No newline at end of file
diff --git a/groupby_index.test.py b/groupby_index.test.py
new file mode 100644
index 0000000..bd79794
--- /dev/null
+++ b/groupby_index.test.py
@@ -0,0 +1,9 @@
+import unittest
+from groupby_index import *
+
+class Test(unittest.TestCase):
+    def test_padding_array(self):
+        self.assertEqual([*map(lambda x:[*x],groupby_index([1,2,3,4],2))],[[1,2],[3,4]])
+
+if __name__ == '__main__':
+    unittest.main()
\ No newline at end of file