Re: [Python-ideas] Repr of lambda
On 17.12.2017 22:20, Serhiy Storchaka wrote:
Currently repr of doesn't contain much of information besides that it
is a lambda.
>>> lambda x: x**2
at 0x7f3479b74488>
All lambdas have the same repr, different only by unreadable
hexadecimal address.
What if include the signature and the expression of the lambda in its
repr?
>>> lambda x: x**2
It's the same for named functions:
In [1]: def ditto(a): return a
In [2]: ditto
Out[2]:
Are you intending to do the same for them?
This would return an old feature of Python 0.9.1
(https://twitter.com/dabeaz/status/934835068043956224).
Repr of function could contain just the signature.
But there is a problem with default values. Their reprs can be very
long, especially in the following case with mutable default value:
def foo(x, _cache={}):
try:
return _cache[x]
except KeyError:
pass
_cache[x] = y = expensive_calculation(x)
return y
Maybe the placeholder should be always used instead of default values.
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--
Regards,
Ivan
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Re: [Python-ideas] Repr of lambda
On 12/17/2017 2:20 PM, Serhiy Storchaka wrote:
Currently repr of doesn't contain much of information besides that it is
a lambda.
>>> lambda x: x**2
at 0x7f3479b74488>
All lambdas have the same repr, different only by unreadable hexadecimal
address.
Having the same pseudo-name is what being anonymous means. Some
consider that a feature ;-).
What if include the signature and the expression of the lambda in its repr?
>>> lambda x: x**2
Printing the return value requires adding a code or function attribute.
The return expression(s), possibly None, would be just as useful for
named functions.
This would return an old feature of Python 0.9.1
(https://twitter.com/dabeaz/status/934835068043956224).
Repr of function could contain just the signature.
But there is a problem with default values. Their reprs can be very
long, especially in the following case with mutable default value:
I would not expect the representation to change; just use the expression.
def foo(x, _cache={}):
try:
return _cache[x]
except KeyError:
pass
_cache[x] = y = expensive_calculation(x)
return y
Maybe the placeholder should be always used instead of default values.
Do you mean 'a placeholder'?
--
Terry Jan Reedy
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[Python-ideas] Repr of lambda
Currently repr of doesn't contain much of information besides that it is
a lambda.
>>> lambda x: x**2
at 0x7f3479b74488>
All lambdas have the same repr, different only by unreadable hexadecimal
address.
What if include the signature and the expression of the lambda in its repr?
>>> lambda x: x**2
This would return an old feature of Python 0.9.1
(https://twitter.com/dabeaz/status/934835068043956224).
Repr of function could contain just the signature.
But there is a problem with default values. Their reprs can be very
long, especially in the following case with mutable default value:
def foo(x, _cache={}):
try:
return _cache[x]
except KeyError:
pass
_cache[x] = y = expensive_calculation(x)
return y
Maybe the placeholder should be always used instead of default values.
___
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Python-ideas@python.org
https://mail.python.org/mailman/listinfo/python-ideas
Code of Conduct: http://python.org/psf/codeofconduct/
