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Numpy arange

arange in NumPy is very like the Python Range callable with two important differences:

  • arange returns an array rather than a range object (Python 3) or a list (Python 2);
  • arange arguments can be floating point values.
>>> import numpy as np

>>> np.arange(4, 11, 2)
array([ 4,  6,  8, 10])
>>> np.arange(4, 11, 0.5)
array([  4. ,   4.5,   5. ,   5.5,   6. ,   6.5,   7. ,   7.5,   8. ,
         8.5,   9. ,   9.5,  10. ,  10.5])

Because arange returns arrays, you can use NumPy element-wise operations to multiply by the step size and add a start value. This is one way to create equally spaced vectors (np.linspace is another):

>>> np.arange(10) * 0.5 + 4
array([ 4. ,  4.5,  5. ,  5.5,  6. ,  6.5,  7. ,  7.5,  8. ,  8.5])