In docstrings, it's important to document the type, because there is no value present to infer it from.  Here you can look at the next line and see that it's 12.  Plus, what else would a size be?

At least can we compromise on a style that makes clearer what's going on here? Google style docstrings use `name (type): description`.  I'd write this comment as:
```
# Default size for randomly-generated passwords (int).
```