The current grammar for decorators is
decorator ::= "@" dotted_name ["(" [argument_list [","]] ")"] NEWLINE
This restricts the decorator syntax to dotted names with an optional call
with an argument list:
@spam.eggsdef f():
...
@ham('foo, 'bar')def g():
...
I love the amount of generality and abstraction in Python, but I think this
is a place where there could be more of that: I think arbitrary expressions
should be allowed; the value of that expression is what gets used as the
decorator, using its *call* method (raising TypeError if the object is not
callable). This would allow things like:
@(lambda x: x)def f():
...
(this currently raises a SyntaxError).
Note that I didn’t come up with this because I have a particular
application in mind, it just irks me that this isn’t possible in Python :-)
! Here is a perhaps slightly more stimulating example:
@(lambda factory: factory())def foo():
# this is a one-use factory for real_foo
call_count = 0 # essentially a static variable
def real_foo():
nonlocal call_count
call_count += 1
return call_count
return real_foo
This is more a “purity” thing than a “practicality” thing, but I don’t
think it has any negative effects on practicality or on the usual use of
decorators.
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