Walrus Operator

The Walrus operator, formally the assignment expressions, has been for some time around now in Python (since 3.8). I’ve grown fond of it :).

You can add more clarity to the code with it:

last_visited_at = context.get("last_visited_at")

if last_visited_at is None:
    raise ValueError(f"last_visited_at should have value (is {last_visited_at})")

vs.

if (last_visited_at := context.get("last_visited_at")) is None:
    raise ValueError(f"last_visited_at should have value (is {last_visited_at})")

The last_visited_at variable should not matter after the conditional block. The example with the walrus operator signals the intent better.

I haven’t yet used the operator for anything fancier but as syntax sugar for better code clarity. RealPython illustrates more uses of the Walrus operator e.g. this one of rewriting a double list comprehension into a single one!