Add Python/keyword-only-arguments.md

Co-authored-by: Richard Lane <[email protected]>

Python/keyword-only-arguments.md

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+# Function arguments that can only be used a keywords, not positional arguments
+
+You can define a keyword-only function in python by using a `*` (everything afterwards will be keyword-only). This can make the meaning of function arguments much clearer, compare:
+
+```python
+my_function(my_data, False, 4, 16, None)
+```
+
+and:
+
+```python
+my_function(my_data, shuffle=False, num_workers=4, batch_size=16, output_file=None)
+```
+
+You'd define this as:
+
+```python
+def my_function(my_data, *, shuffle, num_workers, batch_size, output_file):
+    ...
+```
+
+You can also have [positional-only arguments](https://peps.python.org/pep-0570/), but you probably don't need to do that.
+
+Via: [Richard](https://github.com/richard-lane)