Python: declare type of multiple variables in the same line

Question

If duplicate, please let me know, but I couldn't find an answer. Also, this question does not seem to address the issue.

I'd like to declare type of multiple variables in the same line. Instead of

a: float
b: float
c: float

I'd like to use something like

a, b, c: float

But I get a syntax error. What is the correct syntax?

Answer 1

It doesn't appear to be possible to annotate multiple variables with one annotation statement.

Annotated Assignment Statements defines an annotation as:

annotated_assignment_stmt ::=  augtarget ":" expression
                               ["=" (starred_expression | yield_expression)]

So the augtarget rule dictates what is allowed to go before the colon. augtarget is defined as:

augtarget                 ::=  identifier | attributeref | subscription | slicing

So the only things that can go before the colon is an identifier (i.e. a single variable), an attributeref (an expression followed by .some_attribute_name), a subscription (an expression followed by [some_index]), or a slicing (same syntax as a subscription). a, b, c is not any of these things, so a, b, c: <some type> is not legal syntax.

---

If you merely want to annotate all three variables on one line, and not necessarily in one statement, you can chain independent simple statements together with a semicolon:

a:float; b:float; c:float

... But this is somewhat unsatisfying since you still have to type float three times.