If I have a numpy ndarray of dtype string:
from numpy import array as narray
a = narray(['a', 'b'])
how do I add another string to it? And how do I access that string via an index?
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1 Answer
Check out http://docs.scipy.org/doc/numpy/reference/generated/numpy.insert.html
For example,
numpy.insert( a, 2, 'c' )
would insert c at position 2 in a.
3 Comments
Superdooperhero
Do you need to do a = numpy.insert(a, 2, 'c')? Is this really inefficient due to python having to reallocate space every time?
Benjamin Hodgson
@Superdooperhero - you're right about reallocating space every time. Numpy is not well equipped to deal with arrays that change their length. Try to build your entire set of data in advance using lists before giving it to Numpy to do your calculations. See, for example, this question.
danmcardle
Well I provided the simplest use case. Follow the documentation link and it says that
obj may be a list of indices and values may be a list of values, so any number of inserts could be accomplished in one step. That's about as good as it's gonna get in python.