OpenPyXL学习

Workbooks, Sheets, Cells

As a quick review, here’s a rundown of all the functions, methods, and data types involved in reading a cell out of a spreadsheet file:

1. Import the openpyxl module.

2. Call the openpyxl.load_workbook() function.

3. Get a Workbook object.

4. Call the get_active_sheet() or get_sheet_by_name() workbook method.

5. Get a Worksheet object.

6. Use indexing or the cell() sheet method with row and column keyword arguments.

7. Get a Cell object.

8. Read the Cell object’s value attribute.

setdefault()

for row in range(2, sheet.get_highest_row() + 1):
	# Each row in the spreadsheet has data for one census tract.
	state  = sheet['B' + str(row)].value
    county = sheet['C' + str(row)].value
    pop    = sheet['D' + str(row)].value

	
	# Make sure the key for this state exists.
	#Since setdefault() will do nothing if the key already exists,
	#you can call it on every iteration of the for loop without a problem.
	countyData.setdefault(state, {})
	
	# Make sure the key for this county in this state exists.
   countyData[state].setdefault(county, {'tracts': 0, 'pop': 0})

	# Each row represents one census tract, so increment by one.
	countyData[state][county]['tracts'] += 1
    # Increase the county pop by the pop in this census tract.
	countyData[state][county]['pop'] += int(pop)

Since setdefault() will do nothing if the key already exists, you can call it on every iteration of the for loop without a problem.

Write the Results to a File

# Open a new text file and write the contents of countyData to it.
print('Writing results...')
resultFile = open('census2010.py', 'w')
resultFile.write('allData = ' + pprint.pformat(countyData))
resultFile.close()
print('Done.')

The readCensusExcel.py program was throwaway code: Once you have its results saved tocensus2010.py, you won’t need to run the program again. Whenever you need the county data, you can just runimport census2010.

Project: Updating a Spreadsheet

Step 1: Set Up a Data Structure with the Update Information

A more flexible solution is to store the corrected price information in a dictionary and write your code to use this data structure.

PRICE_UPDATES = {'Garlic': 3.07,
                 'Celery': 1.19,
                 'Lemon': 1.27}

 If you need to update the spreadsheet again, you’ll need to update only the PRICE_UPDATES dictionary, not any other code.