Foxpro goto command and deleted records

MRAB python at mrabarnett.plus.com
Wed Jul 18 19:57:49 CEST 2012


On 18/07/2012 18:28, Ed Leafe wrote:
> On Jul 18, 2012, at 12:16 PM, Ethan Furman wrote:
>
>> Your memory is good!  I typed it in wrong.
>
> 	Well, I was an MVP for Visual Foxpro for 10 years, so...
>
> 	;-)
>
>> I see four other options:
>>
>> 0) don't move the pointer (listed for completeness)
>> 1) go to that record anyway
>> 2) go to the next undeleted record
>> 3) go to the seventh undeleted record (possibly the least practical)
>> 4) raise an exception
>>
>> I still don't like it.  Any opinion on the other four choices?  I'm leaning towards 1, possibly with 4 as an option:
>
> 	#4 is probably the most Pythonic approach. The calling code can then decide how to react to attempting to access a deleted record. Even if you're accessing data stored in VFP tables, your module should be as Pythonic as possible.
>
I disagree. I think that if you can see it should be able to go to it.

I think that the closest analogue is a list, although maybe you should
be able to hide any records which are marked for deletion.

# Print all of the names.
records.include_deleted = True
print("There are {} names".format(len(records)))
for r in records:
     if r.deleted:
         print("\t{} (deleted)".format(r["name"]))
     else:
         print("\t{}".format(r["name"]))

# Print all but the deleted names.
records.include_deleted = False
print("There are {} names".format(len(records)))
for r in records:
     print(r["name"])

>> Part of the reason I feel this is reasonable is that with my dbf module it is possible to create an index that does /not/ include certain records:
>
> 	Deleting a record in VFP doesn't remove it from the index; I believe it marks that index entry as deleted, too. I think that as long as you treat the deleted status as the same as any other boolean column you'll be good.
>



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