I just read the question Why is there no tuple comprehension in Python?
In the comments of the accepted answer, it is stated that there are no true \"tuple comprehensio
To me, it seems like the second example is also one where a generator object is created first. Is this correct?
Yes, you're correct, checkout the CPython bytecode:
>>> import dis
>>> dis.dis("*(thing for thing in thing),")
1 0 LOAD_CONST 0 ( at 0x7f56e9347ed0, file "", line 1>)
2 LOAD_CONST 1 ('')
4 MAKE_FUNCTION 0
6 LOAD_NAME 0 (thing)
8 GET_ITER
10 CALL_FUNCTION 1
12 BUILD_TUPLE_UNPACK 1
14 POP_TOP
16 LOAD_CONST 2 (None)
18 RETURN_VALUE
Is there any difference between these expressions in terms of what goes on behind the scenes? In terms of performance? I assume the first and third could have latency issues while the second could have memory issues (as is discussed in the linked comments).
My timings suggest the first 1 is slightly faster, presumably because the unpacking is more expensive via BUILD_TUPLE_UNPACK than the tuple()
call:
>>> from timeit import timeit
>>> def f1(): tuple(thing for thing in range(100000))
...
>>> def f2(): *(thing for thing in range(100000)),
...
>>> timeit(lambda: f1(), number=100)
0.5535585517063737
>>> timeit(lambda: f2(), number=100)
0.6043887557461858
Comparing the first one and the last, which one is more pythonic?
The first one seems far more readable to me, and also will work across different Python versions.