title: 'int' object is not callable error in python when taking cross-entropy of two lists
body: <p>So I am getting an error called <code>"TypeError: 'int' object is not callable"</code> when I run this code. I did some research and I think it might be due to the fact that the cross entropy variable is declared as a wrong type. I would greatly appreciate some help on figuring out why I'm getting this error. Basically, what I'm doing is taking in two lists and trying to figure out the cross-entropy for the two lists through the code.</p>
  
  <pre><code>import numpy as np
  
  # Write a function that takes as input two lists Y, P,
  # and returns the float corresponding to their cross-entropy.
  def cross_entropy(Y, P):
      Y = np.float_(Y)
      P = np.float_(P)
      crossentropy = 0.0
      for i in range(len(Y)):
          crossentropy+=-1(Y[i]*np.log(P[i]) + (1-Y[i])*np.log(1-P[i]))
      return crossentropy
  </code></pre>