fix refactored the column label generation function and added corresponding unit test.

Author: Luis M. Santos

O365/drive.py

@@ -1606,6 +1606,7 @@ def _base_get_list(self, url, limit=None, *, query=None, order_by=None,
         items = (
             self._classifier(item)(parent=self, **{self._cloud_data_key: item})
             for item in data.get('value', []))
+
         next_link = data.get(NEXT_LINK_KEYWORD, None)
         if batch and next_link:
             return Pagination(parent=self, data=items,

O365/excel.py

@@ -1980,11 +1980,21 @@ def append_rows(self, rows):
         Appends rows to the end of a worksheet. There is no direct Graph API to do this operation without a Table
         instance. Instead, this method identifies the last row in the worksheet and requests a range after that row
         and updates that range.
+
+        Beware! If you open your workbook from sharepoint and delete all of the rows in one go and attempt to append
+        new rows, you will get undefined behavior from the Microsoft Graph API. I don't know if I did not give enough
+        time for the backend to synchronize from the moment of deletion on my browser and the moment I triggered my
+        script, but this is something I have observed. Sometimes insertion fails and sometimes it inserts where the new
+        row would have been if data had not been deleted from the browser side. Maybe it is an API cache issue. However,
+        after the first row is inserted successfully, this undefined behavior goes away on repeat calls to my scripts.
+        Documenting this behavior for future consumers of this API.
+
         :param list[list[str]] rows: list of rows to push to this range. If updating a single cell, pass a list
             containing a single row (list) containing a single cell worth of data.
         """
         row_count = len(rows)
         col_count = len(rows[0]) if row_count > 0 else 0
+        col_index = col_count - 1
 
         # Find the last row index so we can grab a range after it.
         current_range = self.get_used_range()
@@ -2000,7 +2010,7 @@ def append_rows(self, rows):
         target_index = current_range.row_count
 
         # Generate the address needed to outline the bounding rectangle to use to fill in data.
-        col_name = col_index_to_label(col_count)
+        col_name = col_index_to_label(col_index)
         insert_range_address = 'A{}:{}{}'.format(target_index + 1, col_name, target_index + row_count)
 
         # Request to push the data to the given range.

O365/utils/range.py

@@ -1,21 +1,27 @@
-
-CAPITALIZED_ASCII_CODE = 64
+CAPITALIZED_ASCII_CODE = ord('A')
 CAPITALIZED_WINDOW = 26
 
+
 def col_index_to_label(col_index):
     """
-    Given a column index, returns the label corresponding to the column name. For example, index 1 would be
-    A ... until 26 which would be Z.
-    This function will loop until a full label is generated using chunks of 26. Meaning, an index of 52 should
-    yield a label of ZZ corresponding to the ZZ column.
+    Given a column index, returns the label corresponding to the column name. For example, index 0 would be
+    A ... until 25 which would be Z.
+    This function will recurse until a full label is generated using chunks of CAPITALIZED_WINDOW. Meaning,
+    an index of 51 should yield a label of ZZ corresponding to the ZZ column.
 
-    :param int col_index: list of rows to push to this range. If updating a single cell, pass a list
-        containing a single row (list) containing a single cell worth of data.
+    :param int col_index: number associated with the index position of the requested column. For example, column index 0
+        would correspond to column label A.
     """
-    label = chr(CAPITALIZED_ASCII_CODE + col_index % CAPITALIZED_WINDOW)
-    col_index -= CAPITALIZED_WINDOW
+    label = ''
+    extra_letter_index = (col_index // CAPITALIZED_WINDOW) - 1 # Minor adjustment for the no repeat (0) case.
+
+    # If we do need to prepend a new letter to the column label do so recursively such that we could simulate
+    # labels like AA or AAA or AAAA ... etc.
+    if extra_letter_index >= 0:
+        label += col_index_to_label(extra_letter_index)
+
+    # Otherwise, passthrough and add the letter the input index corresponds to.
+    return label + index_to_col_char(col_index)
 
-    while col_index >= CAPITALIZED_WINDOW:
-        label += chr(CAPITALIZED_ASCII_CODE + col_index % CAPITALIZED_WINDOW)
-        col_index -= CAPITALIZED_WINDOW
-    return label
+def index_to_col_char(index):
+    return chr(CAPITALIZED_ASCII_CODE + index % CAPITALIZED_WINDOW)

tests/test_range.py

@@ -0,0 +1,25 @@
+import pytest
+
+from O365.utils import col_index_to_label
+
+
+class TestRange:
+    EXPECTED_CHARS = [
+        'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z',
+        'AA','AB','AC','AD','AE','AF','AG','AH','AI','AJ','AK','AL','AM','AN','AO','AP','AQ','AR','AS','AT','AU','AV','AW','AX','AY','AZ',
+        'BA','BB','BC','BD','BE','BF','BG','BH','BI','BJ','BK','BL','BM','BN','BO','BP','BQ','BR','BS','BT','BU','BV','BW','BX','BY','BZ',
+    ]
+    def setup_class(self):
+        pass
+
+    def teardown_class(self):
+        pass
+
+    def test_col_index_to_label(self):
+        for i in range(len(self.EXPECTED_CHARS)):
+            expected_index = i
+            expected_label = self.EXPECTED_CHARS[expected_index]
+            label = col_index_to_label(i)
+            print(f'Index {i} Letter Index {i} Label {label} Expected {expected_label}')
+
+            assert label == expected_label