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| From | Terry Reedy <tjreedy@udel.edu> |
| Subject | Re: Evaluation order |
| Date | Fri, 10 Jul 2015 08:27:35 -0400 |
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Show key headers only | View raw
On 7/10/2015 8:04 AM, candide wrote: > Le vendredi 10 juillet 2015 04:02:56 UTC+2, Chris Angelico a écrit : >> I'm not sure what contradiction you're referring to, here. The >> evaluation that you're pointing out says, as Terry showed via the >> disassembly, that Python's first action is to look up the name 't' and >> grab a reference to whatever object it points to. > > But in order to perform an operation, the interpreter has to evaluate > the operands and "evaluating" is not "grabbing a reference to". In the CPython, evaluating a name is implemented as getting the reference corresponding to the name. >> The execution of >> t.sort() has to happen before the multiplication, because of the >> parentheses. > Official docs explains what evaluation is : > > When the name is bound to an object, evaluation of the atom yields that object. Conceptually, that is exactly right. How that is implemented on a computer in CPython is to load the address on the top of the virtual machine stack. > So, since the Python interpreter is performing evaluation from left to right, > the first operand of the expression : > > t*(1+int(bool(t.sort()))) > > evaluates to [2020, 42, 2015]. 't' evaluates to the ***mutable*** list that 't' is bound to. > Next, the second operatand evaluates to the integer 1. And in the process of that evaluation, the list is sorted. -- Terry Jan Reedy
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Evaluation order candide <c.candide@laposte.net> - 2015-07-09 17:10 -0700
Re: Evaluation order Terry Reedy <tjreedy@udel.edu> - 2015-07-09 21:45 -0400
Re: Evaluation order Chris Angelico <rosuav@gmail.com> - 2015-07-10 12:02 +1000
Re: Evaluation order candide <c.candide@laposte.net> - 2015-07-10 05:04 -0700
Re: Evaluation order Ned Batchelder <ned@nedbatchelder.com> - 2015-07-10 05:19 -0700
Re: Evaluation order Terry Reedy <tjreedy@udel.edu> - 2015-07-10 08:27 -0400
Re: Evaluation order Chris Angelico <rosuav@gmail.com> - 2015-07-11 00:27 +1000
Re: Evaluation order Mark Lawrence <breamoreboy@yahoo.co.uk> - 2015-07-10 15:49 +0100
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