Lovely, succinct answers.
On 17/11/2018 2:44 AM, Ian Kelly wrote:
On Fri, Nov 16, 2018 at 7:57 AM Steve Keller <keller@no.invalid> wrote:I have looked at generators, generator expressions, and iterators and I try to get more familiar with these. 1. How would I loop over all (with no upper bound) integers or all powers of two, for example? In C it would be for (int i = 0; ; i++) { ... } or for (int i = 1; ; i *= 2) { ... } In Python, I could define a generator def powers(): i = 1 while True: yield(i) i *= 2 for i in powers(): ... More elegant are generator expressions but I cannot think of a way without giving an upper limit: for i in (2 ** i for i in range(1000000)): ... which looks ugly. Also, the double for-loop (and also the two loops in the above exmaple, for + while in the generator) look unnatural, somehow, i.e. loop over all elements which are created by a loop. Is there a more beautyful way?Some options: from itertools import count def powers(): for i in count(): yield 2 ** i for i in (2 ** i for i in count()): ... for i in map(lambda x: 2 ** x, count()): ... from functools import partial from operator import pow for i in map(partial(pow, 2), count()): ... Take your pick.
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