[Python-ideas] The @update operator for dictionaries
jfine2358 at gmail.com
Sat Mar 9 11:34:01 EST 2019
Steven D'Aprano asked me to explain the difference between
> a at update=b
> a at update b
It is the same as the difference between
a += b
a + b
The one uses a._iadd__(b), a.__add__(b) and so on. For the other,
replace 'add' by 'at_update', and '+' by '@update'.
By the way, the expressions
a at update b
a @update b
are to be equivalent, but
a @ update b
is something else (and not valid Python).
> Is this supposed to be unique to update, or will there be an infinite
> number of special dunder methods for arbitrary method names?
There are (many) numbers between 1 and infinity. If a programmer
defines __at_python__ on type(guido) then guido at python will have
> New syntax which breaks existing code is not likely to be
> accepted without a *really* good reason.
I'd like to see some real-world examples of code that would be broken.
As I recall, most or all of the code examples in the python-ideas
thread on the '@' operator actually write ' @ '. So they would be
And if otherwise a good idea, we can use the from __future__ trick to
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