Try ... except ... except ...: how to avoid code repeating

Question

• I would like to avoid writing errorCount += 1in several places.
• I'm looking for a better way than

    success = False
    try:
        ...
    else:
        success = True
    finally:
        if success:
            storage.store.commit ()
        else:
            storage.store.rollback ()

• I try to avoid store.rollback()except in every sentence.

Any idea on how to do this?

count = 0
successCount = 0
errorCount = 0
for row in rows:
    success = False
    count += 1
    newOrder = storage.RepeatedOrder()
    storage.store.add(newOrder)
    try:
        try:
            newOrder.customer = customers[row.customer_id]
        except KeyError:
            raise CustomerNotFoundError, (row.customer_id,)
        newOrder.nextDate = dates[row.weekday]
        _fillOrder(newOrder, row.id)
    except CustomerNotFoundError as e:
        errorCount += 1
        print u"Error: Customer not found. order_id: {0}, customer_id: {1}".format(row.id, e.id)
    except ProductNotFoundError as e:
        errorCount += 1
        print u"Error: Product not found. order_id: {0}, product_id: {1}".format(row.id, e.id)
    else:
        success = True
        successCount += 1
    finally:
        if success:
            storage.store.commit()
        else:
            storage.store.rollback()
print u"{0} of {1} repeated orders imported. {2} error(s).".format(successCount, count, errorCount)

Answer 1

This looks like a possible application of the new withPython operator . This allows you to quickly turn off operations and free up resources, regardless of what the result was a block of code.

PEP 343

Answer 2

logError(), errorCount ( -) . , , :

try:
    # something
except (CustomerNotFoundError, ProductNotFoundError), e:
    logError(e)

, , e.

, : successCount = len(rows) - errorCount

Answer 3

, , ( , , ), , (msg), , , . , , .

Answer 4

If you like to cumulate errors, why don't you cumulate errors? If you put error messages in a list, the size of the list gives the information you need. You can even postprocess something. You can easily decide if an error has occurred and printing is only called in one place.

Answer 5

Well, according to this page, part 7.4:

http://docs.python.org/reference/compound_stmts.html

This is possible with python ver. > = 2.6. I mean try..except..finally construction.