On Mi, 2015-12-23 at 00:34 -0800, Stephan Hoyer wrote: > We have a type similar to this (a typed list) internally in pandas, > although it is restricted to a single dimension and far from feature > complete -- it only has .append and a .to_array() method for > converting to a 1d numpy array. Our version is written in Cython, and > we use it for performance reasons when we would otherwise need to > create a list of unknown length: > https://github.com/pydata/pandas/blob/v0.17.1/pandas/hashtable.pyx#L99 >
Probably is a bit orthogonal since I guess you want/need cython, but pythons buildin array.array should get you there pretty much as well. Of course it requires the C typecode (though that should not be hard to get) and does not support strings. - Sebastian > > In my experience, it's several times faster than using a builtin list > from Cython, which makes sense given that it needs to copy about 1/3 > the data (no type or reference count for individual elements). > Obviously, it uses 1/3 the space to store the data, too. We currently > don't expose this object externally, but it could be an interesting > project to adapt this code into a standalone project that could be > more broadly useful. > > > Cheers, > Stephan > > > > > On Tue, Dec 22, 2015 at 8:20 PM, Chris Barker <chris.bar...@noaa.gov> > wrote: > > > sorry for being so lazy as to not go look at the project > pages, but.... > > > This sounds like it could be really useful, and maybe > supercise a coupl eof half-baked projects of mine. But -- what > does "dynamic" mean? > > > - can you append to these arrays? > - can it support "ragged arrrays" -- it looks like it does. > > > >>> L = ArrayList( [[0], [1,2], [3,4,5], [6,7,8,9]] ) > >>> print(L) > [[0], [1 2], [3 4 5], [6 7 8 9]] > so this looks like a ragged array -- but what do you get when > you do: > > > for row in L: > print row > > > > > >>> print(L.data) > [0 1 2 3 4 5 6 7 8 > is .data a regular old 1-d numpy array? > > > >>> L = ArrayList( np.arange(10), [3,3,4]) > >>> print(L) > [[0 1 2], [3 4 5], [6 7 8 9]] > >>> print(L.data) > [0 1 2 3 4 5 6 7 8 9] > > does an ArrayList act like a numpy array in other ways: > > > L * 5 > > > L* some_array > > > in which case, how does it do broadcasting??? > > > Thanks, > > > -CHB > > > >>> L = ArrayList(["Hello", "world", "!"]) > >>> print(L[0]) > 'Hello' > >>> L[1] = "brave new world" > >>> print(L) > ['Hello', 'brave new world', '!'] > > > > > Nicolas > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > https://mail.scipy.org/mailman/listinfo/numpy-discussion > > > > > > -- > > Christopher Barker, Ph.D. > Oceanographer > > Emergency Response Division > NOAA/NOS/OR&R (206) 526-6959 voice > 7600 Sand Point Way NE (206) 526-6329 fax > Seattle, WA 98115 (206) 526-6317 main reception > > chris.bar...@noaa.gov > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@scipy.org > https://mail.scipy.org/mailman/listinfo/numpy-discussion
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