Linspace not defined on python (jupyter)

I'm running Python 2 on Jupyter and I'm attempting to edit my notebook.

I have the following code:

points=150
x=linspace(0,9*pi,points)
y=e**(-x/10)*cos(x)

plot(x,y,linestyle='None',marker=7,alpha=0.5)
show()

But an error appears:

NameError                                 Traceback (most recent call last)
<ipython-input-6-6ad78f0584e6> in <module>()
   1 points=150
-> 2 x=linspace(0,9*pi,points)
   3 y=e**(-x/10)*cos(x)
   4 
   5 plot(x,y,linestyle='None',marker=7,alpha=0.5)

NameError: name 'linspace' is not defined

I ran the notebook earlier on an institutional network with no error at all.

I'm a bit confused - what is the problem?

Solution

The linspace() function belongs to Numpy. Try importing Numpy first. By convention, it's generally imported as an entire module (np) and then functions are called within the np object:

import numpy as np

points = 150
x = np.linspace(0, 9 * np.pi, points)

x
# array([  0.        ,   0.18976063,   0.37952126,   0.56928189,
#          0.75904252,   0.94880315,   1.13856378,   1.32832441,
#        ...]

Note: Same goes for pi, should be np.pi. The code you were using may have just done from numpy import *, which is why the np. prefix is missing from all the Numpy-specific functions.