Re: csv module and None values
On Aug 25, 8:49 am, Peter Otten __pete...@web.de wrote: JKPeck wrote: On Aug 24, 10:43 pm, John Yeung gallium.arsen...@gmail.com wrote: On Aug 24, 5:00 pm, Peter Otten __pete...@web.de wrote: If I understand you correctly the csv.writer already does what you want: w.writerow([1,None,2]) 1,,2 just sequential commas, but that is the special treatment. Without it the None value would be converted to a string and the line would look like this one: 1,None,2 No, I think he means he is getting w.writerow([1,None,2]) 1,,2 He evidently wants to quote all strings, but doesn't want None to be considered a string. John Exactly so. The requirement of the receiving program, which is out of my control, is that all strings be quoted but a None in a numeric field result in the ,, output rather than . Excel quotes strings conditionally, which doesn't do what is needed in this case. For QUOTE_NONNUMERIC to quote None values makes some sense, but it gets in the way of representing missing values in a numeric field. It would be nice to have a choice here in the dialects. I thought of replacing the None values with float(nan), since that has a numeric type, but unfortunately that results in writing the string (unquoted) nan for the value. So the sentinel approach seems to be the best I can do. How about: import csv, sys class N(int): ... def __str__(self): return ... pseudo_none = N() w = csv.writer(sys.stdout, quoting=csv.QUOTE_NONNUMERIC) w.writerow([1, foo, pseudo_none, bar]) 1,foo,,bar Peter Clever. Thanks, Jon -- http://mail.python.org/mailman/listinfo/python-list
Re: csv module and None values
On Aug 24, 10:43 pm, John Yeung gallium.arsen...@gmail.com wrote: On Aug 24, 5:00 pm, Peter Otten __pete...@web.de wrote: If I understand you correctly the csv.writer already does what you want: w.writerow([1,None,2]) 1,,2 just sequential commas, but that is the special treatment. Without it the None value would be converted to a string and the line would look like this one: 1,None,2 No, I think he means he is getting w.writerow([1,None,2]) 1,,2 He evidently wants to quote all strings, but doesn't want None to be considered a string. John Exactly so. The requirement of the receiving program, which is out of my control, is that all strings be quoted but a None in a numeric field result in the ,, output rather than . Excel quotes strings conditionally, which doesn't do what is needed in this case. For QUOTE_NONNUMERIC to quote None values makes some sense, but it gets in the way of representing missing values in a numeric field. It would be nice to have a choice here in the dialects. I thought of replacing the None values with float(nan), since that has a numeric type, but unfortunately that results in writing the string (unquoted) nan for the value. So the sentinel approach seems to be the best I can do. Thanks, Jon -- http://mail.python.org/mailman/listinfo/python-list
Re: csv module and None values
JKPeck wrote: On Aug 24, 10:43 pm, John Yeung gallium.arsen...@gmail.com wrote: On Aug 24, 5:00 pm, Peter Otten __pete...@web.de wrote: If I understand you correctly the csv.writer already does what you want: w.writerow([1,None,2]) 1,,2 just sequential commas, but that is the special treatment. Without it the None value would be converted to a string and the line would look like this one: 1,None,2 No, I think he means he is getting w.writerow([1,None,2]) 1,,2 He evidently wants to quote all strings, but doesn't want None to be considered a string. John Exactly so. The requirement of the receiving program, which is out of my control, is that all strings be quoted but a None in a numeric field result in the ,, output rather than . Excel quotes strings conditionally, which doesn't do what is needed in this case. For QUOTE_NONNUMERIC to quote None values makes some sense, but it gets in the way of representing missing values in a numeric field. It would be nice to have a choice here in the dialects. I thought of replacing the None values with float(nan), since that has a numeric type, but unfortunately that results in writing the string (unquoted) nan for the value. So the sentinel approach seems to be the best I can do. How about: import csv, sys class N(int): ... def __str__(self): return ... pseudo_none = N() w = csv.writer(sys.stdout, quoting=csv.QUOTE_NONNUMERIC) w.writerow([1, foo, pseudo_none, bar]) 1,foo,,bar Peter -- http://mail.python.org/mailman/listinfo/python-list
csv module and None values
I'm trying to get the csv module (Python 2.6) to write data records like Excel. The excel dialect isn't doing it. The problem is in writing None values. I want them to result in just sequential commas - ,, but csv treats None specially, as the doc says, To make it as easy as possible to interface with modules which implement the DB API, the value None is written as the empty string. I need strings to be quoted but not None values. Is there any way to get around this special None treatment? TIA, Jon Peck -- http://mail.python.org/mailman/listinfo/python-list
Re: csv module and None values
On Aug 24, 11:30 am, JKPeck jkp...@gmail.com wrote: I'm trying to get the csv module (Python 2.6) to write data records like Excel. The excel dialect isn't doing it. The problem is in writing None values. I want them to result in just sequential commas - ,, but csv treats None specially, as the doc says, To make it as easy as possible to interface with modules which implement the DB API, the value None is written as the empty string. I need strings to be quoted but not None values. Is there any way to get around this special None treatment? TIA, Jon Peck Solved the problem myself by giving a writer class to csv.writer that looks for sentinel markers inserted in place of None and wipes them out before writing to a file. Pretty ugly, but it works. Regards, Jon Peck -- http://mail.python.org/mailman/listinfo/python-list
Re: csv module and None values
JKPeck wrote: I'm trying to get the csv module (Python 2.6) to write data records like Excel. The excel dialect isn't doing it. The problem is in writing None values. I want them to result in just sequential commas - ,, but csv treats None specially, as the doc says, To make it as easy as possible to interface with modules which implement the DB API, the value None is written as the empty string. I need strings to be quoted but not None values. Is there any way to get around this special None treatment? If I understand you correctly the csv.writer already does what you want: Python 2.6.2 (release26-maint, Apr 19 2009, 01:58:18) [GCC 4.3.3] on linux2 Type help, copyright, credits or license for more information. import csv, sys w = csv.writer(sys.stdout) w.writerow([1,None,2]) 1,,2 just sequential commas, but that is the special treatment. Without it the the None value would be converted to a string and the line would look like this one: class LooksLikeNone: ... def __str__(self): return None ... w.writerow([1,LooksLikeNone(),2]) 1,None,2 Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: csv module and None values
On Aug 24, 1:30 pm, JKPeck jkp...@gmail.com wrote: I'm trying to get the csv module (Python 2.6) to write data records like Excel. The excel dialect isn't doing it. The problem is in writing None values. I want them to result in just sequential commas - ,, but csv treats None specially, as the doc says, To make it as easy as possible to interface with modules which implement the DB API, the value None is written as the empty string. I need strings to be quoted but not None values. Is there any way to get around this special None treatment? If you need all nonempty strings to be quoted unconditionally, then you are not writing CSV records the way Excel writes CSV records. The csv module is surprisingly good at behaving like Excel, and by default writes strings with quotes only when needed (that is, when the string itself contains commas, quotes, or newlines). If you truly want Excel-style CSVs, just let the csv module do its thing, as pointed out by Peter Otten. From the sounds of it, you have specified QUOTE_NONNUMERIC or perhaps QUOTE_ALL as the quoting property of the dialect you are using. If so, and if this is really what you need except for *your* special None treatment, then using a sentinel is in my opinion as good a way as any to achieve that. John -- http://mail.python.org/mailman/listinfo/python-list
Re: csv module and None values
On Aug 24, 5:00 pm, Peter Otten __pete...@web.de wrote: If I understand you correctly the csv.writer already does what you want: w.writerow([1,None,2]) 1,,2 just sequential commas, but that is the special treatment. Without it the None value would be converted to a string and the line would look like this one: 1,None,2 No, I think he means he is getting w.writerow([1,None,2]) 1,,2 He evidently wants to quote all strings, but doesn't want None to be considered a string. John -- http://mail.python.org/mailman/listinfo/python-list
