Add Assert Is Only A Development Check as a Python TIL

python/assert-is-only-a-development-check.md

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+# Assert Is Only A Development Check
+
+The `assert` keyword is used in Python to write a statement that will check some
+assertion and raise an error if it isn't met. This is only meant to be used as a
+check during development because it can be easily optimized out of the code.
+
+```python
+stuff = None
+
+assert stuff, "We need to have some stuff to proceed"
+
+print(f"We have {stuff or 'something'}!")
+```
+
+If I execute this code with `python`, it will raise on that second line of code.
+
+```bash
+❯ python assert_example.py
+Traceback (most recent call last):
+  File "/Users/lastword/dev/jbranchaud/py-vmt/assert_example.py", line 3, in <module>
+    assert stuff, "We need to have some stuff to proceed"
+           ^^^^^
+AssertionError: We need to have some stuff to proceed
+```
+
+This `assert` statement will be stripped out of the compiled bytecode if the
+`-O` (capital o) flag is used. Notice how running the same file with that flag
+does not lead to an `AssertionError`.
+
+```python
+❯ python -O assert_example.py
+We have something!
+```
+
+If I want to make sanity checks for situations that would be caused by a bug in
+the code, an `assert` statement can be a good candidate. However, if I am making
+runtime checks like validating user input, then an `if` statement and raising
+something like a `ValueError` is better.