Add Create A Range Of Descending Values as a Python TIL

README.md

@@ -10,7 +10,7 @@ working across different projects via [VisualMode](https://www.visualmode.dev/).
 
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+_1760 TILs and counting..._
 
 See some of the other learning resources I work on:
 
@@ -1047,6 +1047,7 @@ If you've learned something here, support my efforts writing daily TILs by
 - [Check If Package Is Installed With Pip](python/check-if-package-is-installed-with-pip.md)
 - [Control Passing Of Time In Tests](python/control-passing-of-time-in-tests.md)
 - [Create A Dummy DataFrame In Pandas](python/create-a-dummy-dataframe-in-pandas.md)
+- [Create A Range Of Descending Values](python/create-a-range-of-descending-values.md)
 - [Dunder Methods](python/dunder-methods.md)
 - [Easy Key-Value Aggregates With defaultdict](python/easy-key-value-aggregates-with-defaultdict.md)
 - [Install With PIP For Specific Interpreter](python/install-with-pip-for-specific-interpreter.md)

python/create-a-range-of-descending-values.md

@@ -0,0 +1,44 @@
+# Create A Range Of Descending Values
+
+A typical use of `range` looks something like this:
+
+```python
+>>> list(range(1, 5))
+[1, 2, 3, 4]
+```
+
+Which is equivalent to this one where we give a `step` value of `1`.
+
+```python
+>>> list(range(1, 5, 1))
+[1, 2, 3, 4]
+```
+
+If we try to create a _negative range_, that is, a range of values in decreasing
+order, we get an empty list.
+
+```python
+>>> list(range(0, -7))
+[]
+```
+
+That's because the `step` value still defaults to `1`. And there are no positive
+steps between `0` and `-7`. So, let's give `range` a `step` value of `-1`.
+
+```python
+>>> list(range(0,-7, -1))
+[0, -1, -2, -3, -4, -5, -6]
+```
+
+One practical use case of a negative range like this is using a list
+comprehension to transform it into a list of the _last seven days_.
+
+```python
+>>> from datetime import datetime, timedelta
+>>> [datetime.now().date() + timedelta(days=days) for days in range(0,-7, -1)]
+[datetime.date(2026, 3, 19), datetime.date(2026, 3, 18), datetime.date(2026, 3, 17), datetime.date(2026, 3, 16), datetime.date(2026, 3, 15), datetime.date(2026, 3, 14), datetime.date(2026, 3, 13)]
+```
+
+Of course this could have been written with a positive range and then
+subtracting the `timedelta`. I like that I have the option of doing this in
+whatever way makes the code most readable.