Equivalent of j in NumPy

Question

What is the equivalent of Octave's j in NumPy? How can I use j in Python?

In Octave:

octave:1> j
ans =  0 + 1i
octave:1> j*pi/4
ans =  0.00000 + 0.78540i

But in Python:

>>> import numpy as np
>>> np.imag
<function imag at 0x2368140>
>>> np.imag(3)
array(0)
>>> np.imag(3,2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: imag() takes exactly 1 argument (2 given)
>>> np.imag(32)
array(0)
>>> 
>>> 0+np.imag(1)
1

Answer 1

In Python, 1j or 0+1j is a literal of complex type. You can broadcast that into an array using expressions, for example

In [17]: 1j * np.arange(5)
Out[17]: array([ 0.+0.j,  0.+1.j,  0.+2.j,  0.+3.j,  0.+4.j])

Create an array from literals:

In [18]: np.array([1j])
Out[18]: array([ 0.+1.j])

Note that what Michael9 posted creates a complex, not a complex array:

In [21]: np.complex(0,1)
Out[21]: 1j
In [22]: type(_)
Out[22]: complex