optional chaining¶

a?.b short-circuits to None when a is None, otherwise evaluates a.b:

city = user?.address.city

transpiles to:

city = None if user is None else user.address.city

chains¶

each ?. introduces a new short-circuit guard. multi-step chains share a temp variable so each prefix is evaluated only once:

country = user?.address?.country

transpiles to:

country = None if user is None else None if (_t := user.address) is None else _t.country

mixed chains — ?. followed by regular . — only guard at the explicit optional steps:

zip = user?.address.zip
# → None if user is None else user.address.zip

a.b?.c works in the obvious way: only the part after a.b is short-circuited through a temp variable

scope¶

?. is recognized in attribute-access expressions only. method calls, subscripts, and arbitrary call expressions on the optional value are not yet supported in the surface syntax — fall back to a guard expression

interaction with ??¶

see none-coalesce operator. ?. composes with ?? without re-evaluating the chained prefix