Update additional formatting to be more explicit about column alignment

docs/api/gptable.md

@@ -71,9 +71,13 @@ you need.
 
 ## Additional formatting
 
-In some cases you may want to apply one-off formatting on specific rows, columns or cells of the data.
+In some cases you may want to apply one-off formatting on specific rows, columns or cells of the data. The formatting options include fonts, colors, patterns, borders, alignment and number formatting.
 As mentioned above, this formatting should not be used to represent data or important information.
 
+#### NOTE
+Columns are automatically aligned based on the [spreadsheet accessibility guidance](https://analysisfunction.civilservice.gov.uk/policy-store/releasing-statistics-in-spreadsheets/). This includes left alignment
+of text outside a table, and row labels inside tables, as well as right alignment of data.
+
 Bespoke formatting can be applied to an individual `GPTable` via the `additional_formatting` parameter,
 when creating a `GPTable` instance. This parameter takes a list of dictionaries, where each dictionary
 defines formatting for one or more rows, columns or cells.

gptables/core/wrappers.py

@@ -570,7 +570,11 @@ def _apply_column_alignments(self, data_table, formats_table, index_columns):
                 value=np.nan,
             ).infer_objects(copy=False)
 
-        data_table_copy = data_table_copy.convert_dtypes()
+        for col in data_table_copy.columns:
+            try:
+                data_table_copy[col] = pd.to_numeric(data_table_copy[col])
+            except Exception:
+                pass
 
         column_types = data_table_copy.dtypes