title: Writing a python function that takes mean of array
body: <p>I am trying to answer the questions below but I don't understand the error code when I run it (Required argument 'object' (pos 1) not found). Any help will be appreciated. </p>
  
  <p>Write a python function that takes in two arrays and returns:
  a) the mean of the first array</p>
  
  <pre><code>def first_mean(a,b):
      a = np.array()
      b = np.array()
      return np.mean(a)
  first_mean([2,3,4],[4,5,6])
  </code></pre>
  
  <p>b) the mean of the second array</p>
  
  <pre><code>def second_mean(a,b):
      a = np.array()
      b = np.array()
      return np.mean(b)
  second_mean([2,3,4],[4,5,6])
  </code></pre>
  
  <p>c) the Mann-Whitney U-statistic and associated p-value of the two arrays?</p>
  
  <pre><code>def mantest(a,b):
      a = np.array()
      b = np.array()
      return scipy.stats.mannwhitneyu(a,b)
  mantest([2,3,4],[4,5,6])
  </code></pre>