Update README about magics. Add pyenv helper script.

Author: neozenith

README.md

@@ -8,6 +8,7 @@ Mini blog to myself about the technical steps to get a python development enviro
 - [PyEnv](#pyenv)
   - [Install / Update](#install--update)
   - [Activate on demand](#activate-on-demand)
+    - [Avoiding magic 🔮](#avoiding-magic-)
   - [List Versions you **CAN** install](#list-versions-you-can-install)
   - [List Versions that **ARE** installed](#list-versions-that-are-installed)
   - [Check and Activate a Version](#check-and-activate-a-version)
@@ -48,11 +49,26 @@ brew install pyenv
 
 ## Activate on demand 
 
-This causes the least magic 🔮 and you have better control over what is activated and when.
+This causes the least magic 🔮* and you have better control over what is activated and when.
 ```sh
 eval "$(pyenv init --path)"
 ```
 
+### Avoiding magic 🔮
+
+
+
+[![The Python environmental protection agency wants to seal it in a cement chamber, with pictorial messages to future civilizations warning them about the danger of using sudo to install random Python packages.](assets/xkcd_1987_python_environment_2x.png)](https://xkcd.com/1987/)
+
+> __*magic 🔮__ --> refers to `pip install poetry` or `pip install awscli` could resolve to installing it into **ANY** of **MANY** different python versions that might exist on your `PATH` and this all depends on the order they resolve.
+>
+> So when trying to upgrade it can get problematic...
+>
+> For example you install `awscli` into `homebrew/python3.8` but then `homebrew upgrade python3` and that now resolves to `hombrew/python3.9`.
+> `awscli` is still resolving first on `PATH` but `pip install --upgrade awscli` is pointing to `homebrew/python3.9`.
+>
+> The main way to avoid this completely and over the top is to use the `python3 -m pip install --upgrade awscli` format of the command, but use the absolute path to the version of python you need like ``
+
 ## List Versions you **CAN** install
 
 ```sh

assets/xkcd_1987_python_environment_2x.png

@@ -0,0 +1,37 @@
+# Standard Library
+import subprocess
+from itertools import groupby
+from pathlib import Path
+
+
+def update_pyenv():
+    """Update with latest information."""
+    PYENV_HOME = Path.home() / ".pyenv"
+    subprocess.run("git pull", capture_output=True, shell=True, text=True, cwd=PYENV_HOME)
+
+
+def tidy_versions():
+    # Get all available versions
+    result = subprocess.run("pyenv install --list", capture_output=True, shell=True, text=True)
+
+    # Get all python versions that are only X.Y.Z format and only digits. No dev or alpha versions etc
+    return {
+        pyversion.strip(): tuple([int(d) for d in pyversion.strip().split(".")])
+        for pyversion in result.stdout.strip().split("\n")
+        if pyversion.strip().startswith("3.") and all([d.isdigit() for d in pyversion.strip().split(".")])
+    }
+
+
+def max_patched_versions():
+    # Group tuples by the minor version number
+    grouped_versions = groupby(tidy_versions().values(), lambda v: v[1])
+    # Tuple sort to get the largest within each group
+    return [
+        ".".join([str(n) for n in list(v)])  # Convert tuple back to dot formatted string
+        for v in sorted([max(g, key=lambda x: x) for k, g in grouped_versions], reverse=True)
+    ]
+
+
+if __name__ == "__main__":
+    update_pyenv()
+    print("\n".join([f"pyenv install {v}" for v in max_patched_versions()[:3]]))