Sergey said:
Peter Otten said:
Sergey said:
Please help, is there way to use sub-expressions in lambda?
For example, if I want to calculate sin(x^2)+cos(x^2) I must code:
lambda x: sin(x*x)+cos(x*x)
How to make x*x to be evaluated once?
(lambda x: [sin(x2) + cos(x2) for x2 in [x*x]][0])(.5) == sin(.5*.5) +
cos(.5*.5)
True
The real answer is of course: Use a function.
But what about something like
lambda x: sin(y)+cos(y) where y=x*x
?
May be this could be a PEP? If there is no straight way to do this.
Or maybe it could be made a part of some other language. When
straightforward mechanisms (in rhis case, function definitins) exist to
avoid repeated computations it's very unlikely that such mangled
constructions will be made a part of Python.
If it *were* considered, you should at least change the "where" to
"for", and extend it to unpacking assignment to allow
lambda x, y: (sin(xx+yy) + cos(xx+yy) for xx, yy = x*x, y*y
regards
Steve
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