How to group identical values and count their frequency in Python?
From this sample set I would expect a histogram of receipt that shows
  two occurrences of receipt 102857 (since that person bought two items
  in one transaction) and one occurrence respectively of receipt 102856
  and of receipt 102858.


Then you want:


  df.groupby('receipt').receipt.count()


receipt
102856    1
102857    2
102858    1
Name: receipt, dtype: int64