title: Sort days of week in the right order in Python
body: <p>I'm importing some data from a csv file in python and create a dataframe called frame5. </p>
  
  <p>I have daily data with the date for each day. So far I have used the following to tranfrom the dates to days of the week.</p>
  
  <pre><code>    frame5['day_of_week']=frame5['date'].dt.dayofweek
      days = {0:'Mon',1:'Tues',2:'Weds',3:'Thurs',4:'Fri',5:'Sat',6:'Sun'}
      frame5['day_of_week'] = frame5['day_of_week'].apply(lambda x: days[x])
  </code></pre>
  
  <p>Then, in order to calculate the daily mean I use:</p>
  
  <pre><code>grouped_day_of_week=frame5.groupby('day_of_week') 
  day_of_week_statistics=grouped_day_of_week['reward'].agg([np.mean,np.size,np.sum])
  </code></pre>
  
  <p>Then I want to make a plot with the daily means. </p>
  
  <p>However, in the dataframe day_of_week_statistics the days appear to be sorted in alphabetical order (each row is the statistics calculated for each day of week). </p>
  
  <p>How can I change the order of the days so that they appear in the right order as "Mon", "Tues","Weds","Thurs","Fri","Sat","Sun"?</p>