python, numpy; How to insert element at the start of an array
Simplest way:
a = np.array([1 + 2j, 5 + 7j])a = np.insert(a, 0, 0)Then:
>>> aarray([ 0.+0.j, 1.+2.j, 5.+7.j])Note that this creates a new array, it does not actually insert the 0 into the original array.
There are several alternatives to np.insert, all of which also create a new array:
In [377]: aOut[377]: array([ 1.+2.j, 5.+7.j])In [378]: np.r_[0, a]Out[378]: array([ 0.+0.j, 1.+2.j, 5.+7.j])In [379]: np.append(0, a)Out[379]: array([ 0.+0.j, 1.+2.j, 5.+7.j])In [380]: np.concatenate([[0], a])Out[380]: array([ 0.+0.j, 1.+2.j, 5.+7.j])In [381]: np.hstack([0, a])Out[381]: array([ 0.+0.j, 1.+2.j, 5.+7.j])In [382]: np.insert(a, 0, 0)Out[382]: array([ 0.+0.j, 1.+2.j, 5.+7.j])