Can anyone explain what this line is doing in python code ?
X.reshape((X.shape[0], 1) + X.shape[1:])
I am using numpy here.
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Why not try it out in the interactive interpreter? – Arya McCarthy May 19 '17 at 07:48
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With that downvote, I will remember it for next time. – Kanu May 19 '17 at 07:55
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I'm not the one that downvoted, but it's still a valid question. One of the great things about Python is that we can test things interactively. – Arya McCarthy May 19 '17 at 07:56
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Basically, this code is changing the shape of X to have an additional (size 1, or singleton if you are used to MATLAB) dimension. So if the shape was previously (3,3,3) it changes it to (3,1,3,3). This doesn't add any data since 3x3x3=3x1x3x3=27 It would probably be used so that the number of dimensions match (for functions that include another array). An equivalent form would be:
X = X[:, None, ...]
For more about why you might want to do this, see here
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Empty would be something like `np.random.rand(3,0,2)`, etc., i.e. a dim of length `0` AFAI understand dims. Also, that `singleton` term used by one more author here - http://stackoverflow.com/a/3551859/3293881 – Divakar May 19 '17 at 07:18
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There should be no spaces between the dots of the ellipsis (`...`) otherwise you may get a syntax error. – MB-F May 19 '17 at 07:44
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@kazemakase That's true [only as of Python 3](https://docs.python.org/3/whatsnew/3.0.html#changed-syntax). – Arya McCarthy May 19 '17 at 07:59