Add some text to packaging (#37)

Author: jorgensd

docs/part1/packaging.md

@@ -2,6 +2,53 @@
 
 To be able to create a python package, we need a folder with the name of the package (in this repository it is called `mypackage`, located under `src/mypackage`), and a `pyproject.toml` file.
 
+## Repository structure
+We recommend using the source layout. See [this chapter](https://py-pkgs.org/04-package-structure.html#the-source-layout) for justification.
+
 
 ## Pyproject.toml
+A [toml](https://toml.io/en/) (Tom's Obivous Minimal Language) file is a plain-text file, consisting of [tables](https://toml.io/en/v1.0.0#table)
+which are a selection of key-value pairs.
+
+An example is 
+```toml
+[project]
+name = "catch_us"
+authors = [
+    {name = "Per Ulv", email = "per@acme.no"},
+    {name = "Bippe Stankelbein", email = "bippe@roadrunner.no"}
+    ]
+version = "x.y.z" 
+description = "Meep Meep"
+# "readme" the description field in your package, 
+# see: https://python-poetry.org/docs/pyproject/#readme
+readme = "README.md" 
+requires-python = ">=3.8"
+# Path to license file, see: https://spdx.org/licenses/
+# for a selection of licenses
+license = {file = "LICENSE"}
+# Direct dependencies
+dependencies = [
+    'acme',
+    'numpy'
+]
+```
+
+### Optional dependencies
+The core functionality of a package (its classes and functions) might not depend on many other packages.
+
+However, to be able to test the code, check for consistency and create coverage reports, one might meed additional dependencies.
+
+One can therefore specify a second table in the `pyproject.toml` file, called
+[project.optional-depencies].
+This is treated as a sub-table of `project`.
+
+For instance, if you want to test your package with [pytest](https://docs.pytest.org/en/7.1.x/), you can add
+```toml
+[project.optional-dependencies]
+test = ["pytest"]
+```
+Then, when installing the package, you call `pip3 install .[test]` instead of `pip3 install .` to get the additional dependencies.
 
+### Other tables
+For options related to coverage reports and code consistency, see the [Coverage](./coverage) and [Linting](./linting.md) section, respectively.

pyproject.toml

@@ -1,28 +1,33 @@
 [build-system] # Require setuptool version due to https://github.com/pypa/setuptools/issues/2938
 requires = ["setuptools>=61.0.0", "wheel"]
 
-
-[project] # See https://python-poetry.org/docs/pyproject/ for more keywords
-name = "mypackage" # Name of your package
-authors = [ # List of authors
-    {name = "Jørgen S. Dokken", email = "dokken@simula.no"}
+ # See https://python-poetry.org/docs/pyproject/ for more keywords for the project table
+[project]
+ # Name of your package
+name = "mypackage"
+authors = [
+    {name = "Jørgen S. Dokken", email = "dokken@simula.no"},
+    {name = "Henrik N. Finsberg", email = "henriknf@simula.no"}
     ]
-version = "0.1.0" # Version number
-description = "Minimal package for adding two numbers" # Short description of package
-readme = "README.md" # Is used for the description field in your package, see: https://python-poetry.org/docs/pyproject/#readme
-requires-python = ">=3.8" # Set requirement for minimal python version
-license = {file = "LICENSE"} # Path to license file, see: https://spdx.org/licenses/ for options
+version = "0.1.0" 
+description = "Minimal package for adding two numbers"
+# "readme" the description field in your package, see: https://python-poetry.org/docs/pyproject/#readme
+readme = "README.md" 
+requires-python = ">=3.8"
+ # Path to license file, see: https://spdx.org/licenses/ for options
+license = {file = "LICENSE"}
+# Direct dependencies
 dependencies = [
     'numpy'
 ]
 
 
 [project.optional-dependencies]
 test = [
-   "flake8", # Checks code for consistency, see: https://flake8.pycqa.org/en/latest/user/error-codes.html
-   "mypy", # Makes sure that typing of input/output is consistent
-   "pytest", # To run test
-   "pytest-cov" # To create coverage reports
+   "flake8", # Formatting: https://flake8.pycqa.org/en/latest/user/error-codes.html
+   "mypy", # Input/Output consistency
+   "pytest", # Testing suite
+   "pytest-cov" # Coverage reports
 ]
 
 docs = [