title: pandas DataFrame round
body: <p>Disclaimer: I am a Python novice</p>
  
  <p>I would like to ask if anyone might know why pandas DataFrames can accept np.round() if the DataFrame is copied from, for example, df.describe(), but it does not work if I create the DataFrame manually using a separately defined key/label strings:</p>
  
  <pre><code>df = {}
  index = [...index list...]
  columns = [...key list...]
  df = pd.DataFrame(index=index, columns=columns)
  </code></pre>
  
  <p>gives "AttributeError: rint" if I insert values and then apply np.round(). If I copy df.describe(), change some values and then do np.round() it works fine. Both are DataFrames so I don't see why the behaviour could be different.</p>
  
  <p>code example</p>
  
  <pre><code>df1 = pd.DataFrame({'foo1' : np.random.randn(5),'foo2' : np.random.randn(5)})
  df1.iloc[:,0] = np.round(df1.iloc[:,0],decimals=3) # works fine
  df1
  
  df2 = {}
  index = ['foo1','foo2','foo3']
  columns = ['oof1','oof2']
  df2 = pd.DataFrame(index=index, columns=columns)
  
  num = 0
  for i in df1.median():
     df2.ix[0,num] = df1.median()[num]
     df2.ix[1,num] = df1.median()[num]
     df2.ix[2,num] = df1.median()[num]
     num += 1
  
  np.around(df2.ix[:,0],decimals=3) # gives 'AttributeError: rint'
  </code></pre>