add exception handling; add description of chart types; enhance comments

Author: mvilain

Diff for: 3.Excel Report/2.add-charts.py

@@ -1,40 +1,80 @@
+#!/usr/bin/which python3
+# 2.add-charts.py
+# loads the Excel pivot_table.xlsx 'Report' workbook created in 1.make-pivot-table.py
+# select the 'Report' sheet to generate the graph
+# select 3 columns by Gender, Product, Total Sales
+# create a pivot table using Gender for y-axis showing Product and Total Sales
+# output to excel
+
 from openpyxl import load_workbook
 from openpyxl.chart import BarChart, Reference
+import os
+import sys
+PROG = os.path.basename(sys.argv[0])
+IN_FILE = os.path.expanduser('pivot_table.xlsx')
+OUT_FILE = os.path.expanduser('barchart.xlsx')
 
 # Read workbook and select sheet
-wb = load_workbook('pivot_table.xlsx')
-sheet = wb['Report']
+if not os.path.exists(IN_FILE):
+    print("{} -- file '{}' not found".format(PROG, IN_FILE))
+    exit(1)
+
+# if the pivot_table.xlsx file has been modified by IntelliJ's ExcelReader,
+# this will throw a 'KeyError' exception, so trap it and handle that
+# NOTE: opening the file with Apple's Numbers or Excel does not cause this error
+try:
+    wb = load_workbook(IN_FILE)
+except KeyError:
+    print("{} -- error opening '{}'... regenerate the file".format(PROG, IN_FILE))
+    exit(1)
+
+try:
+    sheet = wb['Report']  # not defined if Sheet not found...throws KeyError
+    print("{}--> '{}({})'".format(PROG, IN_FILE, sheet), end='', flush=True)
+except KeyError:
+    print("{} -- error opening '{}' -- workbook or sheet not found".format(PROG, IN_FILE))
+    exit(1)
 
 # Active rows and columns
 min_column = wb.active.min_column
 max_column = wb.active.max_column
 min_row = wb.active.min_row
 max_row = wb.active.max_row
+# print('  [active cells=({},{}):({},{})] '.format(min_row,min_column,max_row,max_column))
 
 # Instantiate a barchart
 barchart = BarChart()
 
 # Locate data and categories
+# data reference omits the column with the category headers
 data = Reference(sheet,
                  min_col=min_column+1,
                  max_col=max_column,
                  min_row=min_row,
-                 max_row=max_row)  # including headers
-
+                 max_row=max_row
+                 )
+# categories being displayed are in Column A (e.g.1)
+# don't include the headers in min_row
 categories = Reference(sheet,
                        min_col=min_column,
                        max_col=min_column,
                        min_row=min_row+1,
-                       max_row=max_row)  # not including headers
+                       max_row=max_row
+                       )
 
+# Make chart
 # Adding data and categories
 barchart.add_data(data, titles_from_data=True)
 barchart.set_categories(categories)
 
-# Make chart
-sheet.add_chart(barchart, "B12")
 barchart.title = 'Sales by Product line'
+# chart style
+# plain   1=BW  2=multi-color 3=blue  4=red  5=green  6=purple  7=cyan  8=orange
+# outline 9=BW 10=multi-color 11=blue 12=red 13=green 14=purple 15=cyan 16=orange
+# no error occurs of style > 16
 barchart.style = 5  # choose the chart style
+sheet.add_chart(barchart, "B12")
 
 # Save workbook
-wb.save('barchart.xlsx')
+wb.save(OUT_FILE)
+print(" --> '{}'".format(OUT_FILE))