def get_linked_esu_list(self, usrn):
     """
     function that selects all esus for a determined street
     :param usrn: the unique identifier of a certain street
     :return: list[esu_ids] all esu ids linked to a certain street or
     void in case a street does not have any linked esu
     """
     # executing the query
     esus_query_model = QSqlQueryModel()
     esus_query_model.setQuery(self.queries[9].format(usrn))
     while esus_query_model.canFetchMore():
         esus_query_model.fetchMore()
     n_rows = esus_query_model.rowCount()
     # skip if no esus are linked
     if n_rows == 0:
         return
     else:
         i = 0
         esus_list = []
         # creating a list of ESUs Ids that are linked to the street
         while i <= n_rows - 1:
             model_index = esus_query_model.createIndex(i, 0)
             esu = model_index.data()
             esus_list.append(esu)
             i += 1
         return esus_list
 def check_start_end(self, tol):
     # set the feature counter to 0
     count = 0
     # initialises two virtual objects points (start and end point)
     start_point = self.start_point
     end_point = self.end_point
     # uses the qgis python api to access the ESU Graphic Layer
     esu_layer = self.esu_layer
     # runs the query number 8 to retrieve all streets from the Database
     streets_model = QSqlQueryModel()
     streets_model.setQuery(self.queries[8])
     while streets_model.canFetchMore():
         streets_model.fetchMore()
     n_columns = streets_model.columnCount()
     n_rows = streets_model.rowCount()
     i = 0
     j = 0
     # first loop start (for each street):
     start_end_content = []
     while i <= n_rows - 1:
         self.progress_win.setLabelText("Checking start-end Coordinates...")
         # initialises the state of the checks booleans both to false
         start_ok = False
         end_ok = False
         col_info = []
         while j <= n_columns - 1:
             model_index = streets_model.createIndex(i, j)
             if j == 0:
                 data = model_index.data()
                 col_info.append(data)
             if j == 1:
                 data = model_index.data()
                 col_info.append(data)
             if j == 2:
                 data = model_index.data()
                 col_info.append(data)
             if j >= 3:
                 data = model_index.data()
                 col_info.append(data)
             j += 1
         usrn = col_info[0]
         ref_type = col_info[2]
         desc = col_info[1]
         start_point.set(float(col_info[3]), float(col_info[4]))
         end_point.set(float(col_info[5]), float(col_info[6]))
         # filter the layer "ESU Graphic" for the ESUs Ids returned from the list
         # deal just with the arcs part of multi arcs street
         esus_list = self.get_linked_esu_list(usrn)
         feat_filter = self.build_layer_filter(esus_list)
         feat_request = QgsFeatureRequest()
         feat_request.setFilterExpression(feat_filter)
         # second loop starts (for each arc (ESU) composing the street)
         # iterate through all filtered features and their proximity with the start and end of the street
         features = self.esu_layer.getFeatures(feat_request)
         features.rewind()
         # iterates through features
         for feat in features:
             # check start end points for each of the only if none of the start end points of
             # a ESU on each street is not already matched
             if (start_ok is not True) or (end_ok is not True):
                 result = self.start_end_proximity(start_point, end_point,
                                                   feat, tol)
                 # both dist are ok
                 if result == 3:
                     start_ok = True
                     end_ok = True
                 # just end dist is ok
                 elif result == 2:
                     end_ok = True
                 # just start dist is ok
                 elif result == 1:
                     start_ok = True
             else:
                 break
         # in case of problems
         if not start_ok or not end_ok:
             count += 1
             start_end_item = [str(col_info[0]) + ","]
             # handles the creation of the report on a text file
             if not start_ok and not end_ok:
                 start_end_item.append("(both),")
             if not start_ok and end_ok:
                 start_end_item.append("(start),")
             if start_ok and not end_ok:
                 start_end_item.append("(end),")
             start_end_item.append(str(ref_type) + ",")
             start_end_item.append(str(desc) + "\n")
             start_end_content.append(start_end_item)
         j = 0
         i += 1
     if count == 0:
         self.progress_win.setValue(7)
         return
     else:
         start_end_content.insert(0, self.column_names[5])
         self.progress_win.setValue(7)
         return self.content_to_screen(content_list=start_end_content,
                                       query_model=None,
                                       columns_name_id=None,
                                       no_content_id=8)