For example I have 2 arrays How can I zip a and b so I get ? Answer You can use dstack: If you must have tuples: For Python 3+ you need to expand the zip iterator object. Please note that this is horribly inefficient:
Tag: arrays
Reversed array in numpy?
Numpy tentative tutorial suggests that a[ : :-1] is a reversed a. Can someone explain me how we got there? I understand that a[:] means for each element of a (with axis=0). Next : should denote the number of elements to skip (or period) from my understanding. Answer As others have noted, this is a python slic…
Python’s enumerate in Ruby?
Is something built in for this? It doesn’t need to have it’s members immutable, it just needs to be in the standard library. I don’t want to be the guy who subclasses the Array class to add a Python feature to a project. Does it have a different name in Ruby? Answer Something like this in Py…
Indexing with boolean arrays into multidimensional arrays using numpy
I am new to using numpy and one thing that I really don’t understand is indexing arrays. In the tentative tutorial there is this example: I have no idea why it does that last thing. Can anyone explain that to me? Thanks! Answer Your array consists of: One way of indexing it would be using a list of inte…
Concatenating two one-dimensional NumPy arrays
How do I concatenate two one-dimensional arrays in NumPy? I tried numpy.concatenate: But I get an error: TypeError: only length-1 arrays can be converted to Python scalars Answer Use: The arrays you want to concatenate need to be passed in as a sequence, not as separate arguments. From the NumPy documentation…
How does one find the largest consecutive set of numbers in a list that are not necessarily adjacent?
For instance, if I have a list This algorithm should return [1,2,3,4,5,6,7,8,9,10,11]. To clarify, the longest list should run forwards. I was wondering what is an algorithmically efficient way to do this (preferably not O(n^2))? Also, I’m open to a solution not in python since the algorithm is what mat…
Add single element to array in numpy
I have a numpy array containing: I want to create an array containing: That is, I want to add the first element on to the end of the array. I have tried the obvious: But I get an error saying ValueError: arrays must have same number of dimensions I don’t understand this – the arrays are both just …
How to replace values at specific indexes of a python list?
If I have a list: And then declare two other lists: How can I take to_modify’s elements as index to indexes, then set corresponding elements in to_modify to replacements, i.e. after running, indexes should be [0,0,3,0,1,0]. Apparently, I can do this through a for loop: But is there other way to do this?…
How do I remove all zero elements from a NumPy array?
I have a rank-1 numpy.array of which I want to make a boxplot. However, I want to exclude all values equal to zero in the array. Currently, I solved this by looping the array and copy the value to a new array if not equal to zero. However, as the array consists of 86 000 000 values and I have
Immutable numpy array?
Is there a simple way to create an immutable NumPy array? If one has to derive a class from ndarray to do this, what’s the minimum set of methods that one has to override to achieve immutability? Answer You can make a numpy array unwriteable: Also see the discussion in this thread: http://mail.scipy.org…