[Tutor] Data conversion

[Joe Aquilina]

On 19/05/11 13:53, Andre Engels wrote:
> On Thu, May 19, 2011 at 6:36 AM, Joe Aquilina<joe at chem.com.au>  wrote:
>
>> I am new to this list and very much a beginner to Python. Please excuse me
>> if this is a silly question, but in all my searches this morning I have not
>> been able to find an answer.
>>
>> I have a (single table) database file (SQLite3). It has one table, call it
>> literature, with an integer, autoincrement primary key field. I have created
>> a data entry form in Python that I want to use to enter new rows into this
>> database file. On the data entry form I will enter the values for a new
>> table row - all except the primary key field.
>>
>> What I want to be able to do is to have my data entry form autoincrement
>> this primary key field for me, with no ability to change the contents on the
>> data entry form, and save this incremented value as the value of the num
>> field when I save the new row.
>>
>> So for example, if the last row in the table has a value of 256 in the num
>> field, I want the value of 257 to be saved as the value of the num field
>> into the new row I am adding, without having to see or or enter this new
>> value (or indeed the previous value) on the data entry screen.
>>
>> I hope this makes sense. But how do I do this?
>>
>> I thought about doing a
>>
>> SELECT num FROM literature;
>>
>> from the table, then getting the contents of the num field of the last row
>> in the data that a fetchall() retrieves and incrementing it to save with the
>> new row.
>>
>> However, the fetchall() returns the data as tuples, not integers and I don't
>> know how to convert from a tuple data type to an integer to make this work.
>>
>> Is this possible? Or can I achieve my objective in some other way?
>>
>> Any advice/assistance would be appreciated. Thanks in advance.
> l assume the tuple is a 1-tuple?
>
> Anyway, let fetch be the name of your tuple, then
>
> fetch[0]
>
> will be the first element of the tuple,
>
> fetch[1]
>
> the second element, and so on.
>
>
Hello Andre.

I realised after I read your response that I probably hadn't included 
enough information, partly due to my  inexperience in Python and partly 
due to haste on my part.

AFter my original post, I had a little play in Python and was able to 
create this tuple:

[1, 2, 3, 4, 5]

from which I was able to extract any item I wanted as an integer and 
work with as I wanted. I am guessing that this is a 1-tuple.

It is when I do the fetchall() from the table, that I get the following:

[(1,), (2,), (3,)]

I don't know enough to know whether this is a 1-tuple or not. It is from 
this tuple that I want to extract the 3 as an integer so that I can 
increment it and save as an integer into the next row in the table.

Hope that is a little clearer.

Cheers.

Joe Aquilina