Encourage editable install in exercise 1

Author: ashwinvis

content/packaging-example-project/test.py

@@ -1,5 +1,6 @@
 from calculator import add, subtract, integral
 
-print(add(2, 3))
-print(subtract(2, 3))
-print(integral(lambda x: x * x, 0.0, 1.0))
+print("2 + 3 =", add(2, 3))
+print("2 - 3 =", subtract(2, 3))
+integral_x_squared, error = integral(lambda x: x * x, 0.0, 1.0)
+print(f"{integral_x_squared = }")

content/packaging-example-project/test_editable.py

@@ -0,0 +1,3 @@
+from calculator import subtract
+
+print("2 - 3 =", subtract(2, 3))

content/packaging.rst

@@ -128,11 +128,21 @@ Exercises 1
    - Create a new folder outside of our example project
    - Create a new virtual environment (:ref:`dependency_management`)
    - Install the example package from the project folder
-     into the new environment: ``$ pip install /path/to/project-folder/``
+     into the new environment::
+
+        pip install --editable /path/to/project-folder/
+
    - Test the local installation:
 
    .. literalinclude:: packaging-example-project/test.py
 
+   - Make a change in the ``subtract`` function above such that it always
+     returns a float ``return float(x - y)``.
+
+   - Open a new Python console and test the following lines. Compare it with
+     the previous output.
+
+   .. literalinclude:: packaging-example-project/test_editable.py
 
 Sharing packages via PyPI
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