Converting integer array to binary array in python

I am trying to convert an array with integers to binary, using python 2.7.

A simplified version of my code is the following:

 #!/usr/bin/python
 import numpy as np

 a=np.array([6,1,5,0,2])
 b=np.array(np.zeros((5)))

for i in range(10):
    b[i]=bin(int(a[i])).zfill(8)

The code gives me the error message:

b[i]=bin(int(a[i])).zfill(8)
ValueError: invalid literal for float(): 0000b110

What is wrong with my code? Is there another way to do this? The original code is part of a much greater project with 2 dimensional arrays.

p.s I'm a relative novice to Python