example plugin to read a spreadsheet attached in the json ( with Input_viewAttachDocument )

dream/plugins/ExampleReadAttachedSpreadsheet.py

+from copy import copy
+import json
+import time
+import random
+import operator
+import StringIO
+import xlrd
+
+from dream.plugins import plugin
+
+class ExampleReadAttachedSpreadsheet(plugin.OutputPreparationPlugin):
+  """ Example on how to read an excel spreadsheet 
+  """
+
+  def preprocess(self, data):
+    """ Example showing how to read an attached file
+    """
+    # Attachement is encoded in data uri, ie data:application/excel;base64,***
+    data_uri_encoded_input_data = data['input'][self.configuration_dict['input_id']]
+    mime_type, attachement_data = data_uri_encoded_input_data[len('data:'):].split(';base64,', 1)
+    attachement_data = attachement_data.decode('base64')
+    
+    workbook = xlrd.open_workbook(file_contents=attachement_data)
+
+    print "This spreadsheet contains sheets:", workbook.sheet_names()
+
+    raise ValueError(workbook.sheet_names())
+    
+    return data
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