From 16f21d29d26b74a349bc9fee43dcc3128013be22 Mon Sep 17 00:00:00 2001
From: "Joseph T. Iosue" <jtiosue@gmail.com>
Date: Wed, 31 Aug 2022 16:13:11 -0400
Subject: [PATCH] v1.2.5 (#42)

* incremented version

* Update test_subgraph.py

* Update _subgraph.py

* Update test_subgraph.py

* Update README.rst

* Update requirements-dev.txt
---
 README.rst                   | 2 +-
 qubovert/_version.py         | 2 +-
 qubovert/utils/_subgraph.py  | 4 ++++
 tests/utils/test_subgraph.py | 8 ++++++++
 4 files changed, 14 insertions(+), 2 deletions(-)

diff --git a/README.rst b/README.rst
index 9851651..b3ac79d 100644
--- a/README.rst
+++ b/README.rst
@@ -96,7 +96,7 @@ Create the boolean objective function to minimize
     # create the variables
     x = {i: boolean_var('x(%d)' % i) for i in range(N)}
 
-    # minimize \sum_{i=0}^{N-1} (1-2x_{i}) x_{i+1}
+    # minimize \sum_{i=0}^{N-2} (1-2x_{i}) x_{i+1}
     model = 0
     for i in range(N-1):
         model += (1 - 2 * x[i]) * x[i+1]
diff --git a/qubovert/_version.py b/qubovert/_version.py
index a3ba853..72910b1 100644
--- a/qubovert/_version.py
+++ b/qubovert/_version.py
@@ -20,7 +20,7 @@
 )
 
 
-__version__ = "1.2.4"
+__version__ = "1.2.5"
 __author__ = "Joseph T. Iosue"
 __authoremail__ = "jtiosue@gmail.com"
 __license__ = "Apache Software License 2.0"
diff --git a/qubovert/utils/_subgraph.py b/qubovert/utils/_subgraph.py
index 4444923..e6040c6 100644
--- a/qubovert/utils/_subgraph.py
+++ b/qubovert/utils/_subgraph.py
@@ -90,6 +90,8 @@ def subgraph(G, nodes, connections=None):
         value += D.get(key, 0)
         if value:
             D[key] = value
+        else:
+            D.pop(key, 0)
 
     return D
 
@@ -134,5 +136,7 @@ def subvalue(values, G):
         value += D.get(key, 0)
         if value:
             D[key] = value
+        else:
+            D.pop(key, 0)
 
     return D
diff --git a/tests/utils/test_subgraph.py b/tests/utils/test_subgraph.py
index 0d018f5..0c38dbc 100644
--- a/tests/utils/test_subgraph.py
+++ b/tests/utils/test_subgraph.py
@@ -44,6 +44,10 @@ def test_subgraph():
     with assert_raises(ValueError):
         subgraph({0: 1, (0, 1): 1}, {})
 
+    # from Issue #38 in GitHub
+    G = {(2,): 1, (2, 3): -1}
+    assert subgraph(G, {2}, {3: 1}) == {}
+
 
 def test_subvalue():
 
@@ -65,3 +69,7 @@ def test_subvalue():
     # edge case
     assert subvalue({}, G) == G
     assert subvalue({0: 0, 1: 0, 2: 0}, G) == {(): 2}
+
+    # from Issue #38 in GitHub
+    G = {(2,): 1, (2, 3): -1}
+    assert subvalue({3: 1}, G) == {}