On 1 Jul 2020, at 18:54, Brandt Bucher wrote:
Walter Dörwald wrote:
This looks strange to me. In all other cases of variable lookup the
global variable z would be found.
The next case assigns to z, making z local to whereis. This is
consistent with python's existing scoping rules (for example, try
rewriting this as the equivalent if-elif chain and you'll get the same
error). It sounds like you want to add "global z" to the top of the
function definition.
whereis(23) however works.
This branch is hit before the unbound local lookup is attempted.
OK, understood.
However I still find the rule "dotted names are looked up" and "undotted
names are matched" surprising and "case .constant" ugly.
A way to solve this would be to use "names at the top level are always
looked up".
With this the constant value pattern:
case .name:
could be written as:
case name:
The capture pattern (of which there can only be one anyway) could then
be written as:
case object(name):
instead of
case name:
Or we could use "matches are always done against a match object", i.e.
the code from the example would look like this:
from dataclasses import dataclass
@dataclass
class Point:
x: int
y: int
z = 42
def whereis(point):
w = 23
match point as m:
case Point(0, 0):
print("Origin")
case Point(0, m.y):
print(f"Y={m.y}")
case Point(m.x, 0):
print(f"X={m.x}")
case Point():
print("Somewhere else")
case w:
print("Not the answer")
case z:
print("The answer")
case object(z):
print(f"{z!r} is not a point")
Servus,
Walter
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