title: Iterating through pandas dataframe and appending to a list
body: <p>I have a pandas dataframe df</p>
  
  <pre><code>    Date          SKU     Balance
  0   1/1/2017        X1       8
  1   2/1/2017        X2      45
  2   3/1/2017        X1      47
  3   4/1/2017        X2      16
  4   5/1/2017        X1      14
  5   6/1/2017        X2      67
  6   7/1/2017        X2       9
  8   8/1/2017        X1      66
  9   9/1/2017        X1     158
  </code></pre>
  
  <p>I wanna break it and append it to a list so that each item in the list is the collection of 4 days of the data frame </p>
  
  <p>For Example </p>
  
  <p>List[1]</p>
  
  <pre><code>    Date          SKU     Balance
  0   1/1/2017        X1       8
  1   2/1/2017        X2      45
  2   3/1/2017        X1      47
  3   4/1/2017        X2      16
  </code></pre>
  
  <p>List[2]</p>
  
  <pre><code>     Date          SKU     Balance
  0   2/1/2017        X2      45
  1   3/1/2017        X1      47
  2   4/1/2017        X2      16
  3   5/1/2017        X1      14
  </code></pre>
  
  <p>At the moment I can only achieve by appending one day for each list by this below code</p>
  
  <pre><code>dr = pd.date_range('20170101','20170109')
  
  list=[]
  for d in dr:
     list.append(df.loc[df.Date.isin([d])])
  </code></pre>
  
  <p>As mentioned above,How can I append 4 days from the 1st day in one list and loop it to the 2nd day , append another 4 days of rows and so on.</p>
  
  <p>Highly appreciate your help</p>