diff --git a/.github/workflows/pythonpackage.yml b/.github/workflows/pythonpackage.yml
new file mode 100644
index 0000000..3af6c93
--- /dev/null
+++ b/.github/workflows/pythonpackage.yml
@@ -0,0 +1,33 @@
+name: Python package
+
+on: [push]
+
+jobs:
+  build:
+
+    runs-on: ubuntu-latest
+    strategy:
+      max-parallel: 4
+      matrix:
+        python-version: [3.6, 3.7]
+
+    steps:
+    - uses: actions/checkout@v1
+    - name: Set up Python ${{ matrix.python-version }}
+      uses: actions/setup-python@v1
+      with:
+        python-version: ${{ matrix.python-version }}
+    - name: Install dependencies
+      run: |
+        python -m pip install --upgrade pip
+        pip install -r requirements.txt
+        python setup.py build_ext --inplace
+    - name: Lint with pylint
+      run: |
+        pip install pylint
+        # stop the build if there are Python syntax errors or undefined names
+        pylint example
+    - name: Test with pytest
+      run: |
+        pip install pytest
+        pytest
diff --git a/example/__init__.py b/example/__init__.py
index 4448d42..90e5e7a 100644
--- a/example/__init__.py
+++ b/example/__init__.py
@@ -1,4 +1,4 @@
 """Template for a Python Package."""
 
 from ._example import *
-from .submodule import *
\ No newline at end of file
+from .submodule import *
diff --git a/example/submodule.py b/example/submodule.py
index d3c0493..1eab4ed 100644
--- a/example/submodule.py
+++ b/example/submodule.py
@@ -2,19 +2,19 @@
 
 from typing import TypeVar, Iterable, Tuple
 
-T = TypeVar('T', int, float, complex)
-Vector = Iterable[Tuple[T, T]]
-
 import numpy
 
+TNum = TypeVar('T', int, float, complex)
+Vector = Iterable[Tuple[TNum, TNum]]
+
 __all__ = ['cross_2d']
 
-def cross_2d(a: Vector, b: Vector):
+def cross_2d(vec1: Vector, vec2: Vector):
     """Return the z coordinate of a cross product for 2D vectors.
-    
+
     >>> cross_2d((1, 0), (1, 0))
-    0
+    array(0)
     >>> cross_2d((1, 0), (0, 1))
-    1
+    array(1)
     """
-    return a[0]*b[1]-a[1]*b[0]
\ No newline at end of file
+    return numpy.array(vec1[0]*vec2[1]-vec1[1]*vec2[0])