util: add function "chunks"

taken from ElectrumX
67111a3c4c/electrumx/lib/util.py (L149)

electrum/tests/test_util.py

@@ -1,7 +1,7 @@
 from decimal import Decimal
 
 from electrum.util import (format_satoshis, format_fee_satoshis, parse_URI,
-                           is_hash256_str)
+                           is_hash256_str, chunks)
 
 from . import SequentialTestCase
 
@@ -104,3 +104,9 @@ class TestUtil(SequentialTestCase):
         self.assertFalse(is_hash256_str('qweqwe'))
         self.assertFalse(is_hash256_str(None))
         self.assertFalse(is_hash256_str(7))
+
+    def test_chunks(self):
+        self.assertEqual([[1, 2], [3, 4], [5]],
+                         list(chunks([1, 2, 3, 4, 5], 2)))
+        with self.assertRaises(ValueError):
+            list(chunks([1, 2, 3], 0))

electrum/util.py

@@ -520,6 +520,14 @@ def is_non_negative_integer(val) -> bool:
     return False
 
 
+def chunks(items, size: int):
+    """Break up items, an iterable, into chunks of length size."""
+    if size < 1:
+        raise ValueError(f"size must be positive, not {repr(size)}")
+    for i in range(0, len(items), size):
+        yield items[i: i + size]
+
+
 def format_satoshis_plain(x, decimal_point = 8):
     """Display a satoshi amount scaled.  Always uses a '.' as a decimal
     point and has no thousands separator"""