title: Error: 'float' object does not support item assignment
body: <p>I'm programming in python and I don't understand what i'm doing wrong:</p>
  
  <pre><code>import numpy as np
  import matplotlib.pyplot as plt
  from math import exp
  x=np.linspace(0.0,4.0,100)
  y1=x
  for i in range(100):
  
     y2[i]=1.5*(1-exp(-x[i]))
  </code></pre>
  
  <p>This last line gives me an error that says: float object does not support item assigment. I don't understand how y2 can be considered a float object since it is a list in which every element is calculated with 1.5*(1-exp(-x[i])).</p>