Missed this mail. Thanks Derek For the clarification provided. Kind Rgds, Vinodhini
> On 31 Dec 2017, at 10:11 am, Derek Homeier > <de...@astro.physik.uni-goettingen.de> wrote: > > On 30 Dec 2017, at 5:38 pm, Vinodhini Balusamy <me.vi...@gmail.com> wrote: >> >> Just one more question from the details you have provided which from my >> understanding strongly seems to be Design >> [DEREK] You cannot create a regular 2-dimensional integer array from one row >> of length 3 >>> and a second one of length 0. Thus np.array chooses the next most basic >>> type of >>> array it can fit your input data in >> > Indeed, the general philosophy is to preserve the structure and type of your > input data > as far as possible, i.e. a list is turned into a 1d-array, a list of lists > (or tuples etc…) into > a 2d-array,_ if_ the sequences are of equal length (even if length 1). > As long as there is an unambiguous way to convert the data into an array (see > below). > >> Which is the case, only if an second one of length 0 is given. >> What about the case 1 : >>>>> x12 = np.array([[1,2,3]]) >>>>> x12 >> array([[1, 2, 3]]) >>>>> print(x12) >> [[1 2 3]] >>>>> x12.ndim >> 2 >>>>> >>>>> >> This seems to take 2 dimension. > > Yes, structurally this is equivalent to your second example > >> also, >>>> x12 = np.array([[1,2,3],[0,0,0]]) >>>> print(x12) > [[1 2 3] > [0 0 0]] >>>> x12.ndim > 2 > >> I presumed the above case and the case where length 0 is provided to be >> treated same(I mean same behaviour). >> Correct me if I am wrong. >> > In this case there is no unambiguous way to construct the array - you would > need a shape (2, 3) > array to store the two lists with 3 elements in the first list. Obviously > x12[0] would be np.array([1,2,3]), > but what should be the value of x12[1], if the second list is empty - it > could be zeros, or repeating x12[0], > or simply undefined. np.array([1, 2, 3], [4]]) would be even less clearly > defined. > These cases where there is no obvious “right” way to create the array have > usually been discussed at > some length, but I don’t know if this is fully documented in some place. For > the essentials, see > > https://docs.scipy.org/doc/numpy/reference/routines.array-creation.html > > note also the upcasting rules if you have e.g. a mix of integers and reals or > complex numbers, > and also how to control shape or data type explicitly with the respective > keywords. > > Derek > > _______________________________________________ > NumPy-Discussion mailing list > NumPy-Discussion@python.org > https://mail.python.org/mailman/listinfo/numpy-discussion _______________________________________________ NumPy-Discussion mailing list NumPy-Discussion@python.org https://mail.python.org/mailman/listinfo/numpy-discussion
