Re: [Tutor] Handling 'None' (null) values when processing sqlite cursorresults
Monte Milanuk memila...@gmail.com wrote (104, None, u'Sylvester', None, u'Evans', None, u'527-9210 Proin Av.', u'Liberal', u'VT', u'24742', u'1-135-197-1139', u'vehicula.pellentes...@idmollis.edu', u'2010-07-13 22:52:50', u'2010-07-13 22:52:50') At first I was having fits as str.join() was giving me a 'NoneType error'. I found one way around that, by processing the results so the 'None' values got omitted from the list by the time they got to str.join(). Keep the storage and manipulation of data separate from the display of that data. That is an important and fundamental principle of data processing. Store the data with the nulls. Display the data without. values omitted really messed with the list order which I was depending on i.e. list[5] could be different fields depending on how many 'None' And that is why. values had been omitted. And if I didn't omit them, when I printed out the user name in the format 'first''middle''last' from the above record, You need a display function that can strip out the nulls as needed. A simple list comprehension or generator expression would work in this case: print ' '.join(str(field) for field in data if field is not 'None') If you use a Class to model your data you can write a __str__() method that does the intellifgent production of a string fit for printing. Then you just print the records as normal. But for this scenario the complexity of building a class may not be worth it. The key principle is do not try to store your data in a display format. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Handling 'None' (null) values when processing sqlite cursorresults
On 14/07/2010 14:32, Alan Gauld wrote: Monte Milanuk memila...@gmail.com wrote (104, None, u'Sylvester', None, u'Evans', None, u'527-9210 Proin Av.', u'Liberal', u'VT', u'24742', u'1-135-197-1139', u'vehicula.pellentes...@idmollis.edu', u'2010-07-13 22:52:50', u'2010-07-13 22:52:50') At first I was having fits as str.join() was giving me a 'NoneType error'. I found one way around that, by processing the results so the 'None' values got omitted from the list by the time they got to str.join(). Keep the storage and manipulation of data separate from the display of that data. That is an important and fundamental principle of data processing. Store the data with the nulls. Display the data without. values omitted really messed with the list order which I was depending on i.e. list[5] could be different fields depending on how many 'None' And that is why. values had been omitted. And if I didn't omit them, when I printed out the user name in the format 'first''middle''last' from the above record, You need a display function that can strip out the nulls as needed. A simple list comprehension or generator expression would work in this case: print ' '.join(str(field) for field in data if field is not 'None') The problem with that is if you're relying on a set delimiter you are removing elements so you would be better served by doing `str(field) if field != None else '' for field in record` -- Kind Regards, Christian Witts ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Handling 'None' (null) values when processing sqlite cursorresults
Christian Witts cwi...@compuscan.co.za wrote You need a display function that can strip out the nulls as needed. A simple list comprehension or generator expression would work in this case: print ' '.join(str(field) for field in data if field is not 'None') The problem with that is if you're relying on a set delimiter you are removing elements so you would be better served by doing `str(field) if field != None else '' for field in record` True, although in this case we do seem to have a fixed condition since it's the database's representation of null but I originally didn't notice the quotes around None. When I fixed that I should have changed is to equals.. print ' '.join(str(field) for field in data if field != 'None') But your modification confuses me. can you explain? What would the print line look like? Alan G. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Handling 'None' (null) values when processing sqlite cursorresults
On 7/14/10 5:32 AM, Alan Gauld wrote: The key principle is do not try to store your data in a display format. Never was my intention. I just hadn't anticipated needing to write my own function to handle something as (I would think) common as a NULL value in a database field. I had been working with something very simple like: for lines in cursor.fetchall() title = lines[1] first = lines[2] mid = lines[3] last = lines[4] ... print %s %s %s %s % (title, first, mid, last) print %s % (street) print %s, %s %s % (city, state, zipcode) print %s % (phone) print %s % (email) etc. etc. for one format (supposed to look like a mailing label, more or less), and then I was going to experiment with other formatting later. I'll work with the stuff you all have provided as I get time... thanks a bunch! Monte ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
Re: [Tutor] Handling 'None' (null) values when processing sqlite cursorresults
On 14/07/2010 19:34, Alan Gauld wrote: Christian Witts cwi...@compuscan.co.za wrote You need a display function that can strip out the nulls as needed. A simple list comprehension or generator expression would work in this case: print ' '.join(str(field) for field in data if field is not 'None') The problem with that is if you're relying on a set delimiter you are removing elements so you would be better served by doing `str(field) if field != None else '' for field in record` True, although in this case we do seem to have a fixed condition since it's the database's representation of null but I originally didn't notice the quotes around None. When I fixed that I should have changed is to equals.. print ' '.join(str(field) for field in data if field != 'None') But your modification confuses me. can you explain? What would the print line look like? Alan G. ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor I prefer not to use a space delimiter, generally a pipe |, so the output would look a lot like 104||Sylvester||Evans||527-9210 Prion Av.|Liberal|VT|24742|1-135-197-1139|vehicula.pellentes...@idmollis.edu|2010-07-13 22:52:50|2010-07-13 22:52:50 The reason I suggested that usage instead is because Monte said having the 'None' values omitted really messed with the list order which I was depending on So if you're wanting to create a new list which removes the Nones but still keeps the same indexing it would be the way to do it, imho. -- Kind Regards, Christian Witts ___ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor
