Re: Beginner: Data type conversion question
On Jan 15, 11:35 pm, Terry Reedy tjre...@udel.edu wrote: flagg wrote: I am still fairly new to python and programming in general. My question is regardingdataconversion, I am working on a script that will edit dns zone files, one of the functions i wrote handles updating the serial number. Our zone files use the date as the first part of the serial and a two digit integer as the last two. i.e. 2009011501. The next update would be 2009011502, etc Here is the function I wrote, I am using dnspython for reading in zone files as Zone objects. Because dnspython's built-in serial updater will not work with how we format our serial's, I have to re-write it. def checkSerial(): Checks the current 'date' portion of the serial number and checks the current 'counter'(the two digit number at the end of the serial number), then returns a complete new serial currentDate = time.strftime(%Y%m%d, time.localtime()) for (name, ttl, rdata) in zone.iterate_rdatas(SOA): date = str(rdata.serial)[0:8] inc = str(rdata.serial)[8:10] If rdate.serial is already a string, as name would imply, the str() call is pointless. If not, can you get inc as int more directly? if date == currentDate: int(inc) + 1 print inc newInc = str(inc).zfill(2) serial = date + newInc print date is the same return serial elif date currentDate: newInc = 01.zfill(2) serial = currentDate + newInc print date is different return serial Through all of this I am doing a lot ofdatatypeconversion. string - integer, integer back to string, etc. Is this an efficient way of handling this? I have to perform basic addition on the inc variable, but also need to expose that value as a string. What I have above does work, but I can't help but think there is a more efficient way. I guess I am not used todatatypes being converted so easily. Other than that, you are perhaps worrying too much, even if code could be squeezed more. The idea that every object knows how to convert itself to a string representation is basic to Python. tjr Actually when i run a type(serial) on that variable it returns a long which i am not sure why dnspython uses a long variable to store the serial. But you could be right about me worrying to much. The other languages I have dabbled in (java, perl) I don't remember type conversion being as simple. But again I am still new, so don't quote me on that :) -- http://mail.python.org/mailman/listinfo/python-list
Re: Beginner: Data type conversion question
On Jan 15, 11:43 pm, Marc 'BlackJack' Rintsch bj_...@gmx.net wrote: On Thu, 15 Jan 2009 21:09:43 -0800, flagg wrote: def checkSerial(): Checks the current 'date' portion of the serial number and checks the current 'counter'(the two digit number at the end of the serial number), then returns a complete new serial currentDate = time.strftime(%Y%m%d, time.localtime()) The format string can be written as *one* string literal instead of three: %Y%m%d. for (name, ttl, rdata) in zone.iterate_rdatas(SOA): date = str(rdata.serial)[0:8] inc = str(rdata.serial)[8:10] Here you are converting `rdata.serial` twice. tmp = str(rdata.serial) date = tmp[0:8] inc = int(tmp[8:10]) As `inc` is conceptually a number, you should do theconversionhere and treat it as number from now on. if date == currentDate: int(inc) + 1 print inc newInc = str(inc).zfill(2) serial = date + newInc print date is the same return serial elif date currentDate: newInc = 01.zfill(2) serial = currentDate + newInc print date is different return serial Both branches do almost the same. You should try to avoid such code duplication. if date == currentDate: inc += 1 elif date currentDate: inc = 1 else: assert False # Should never happen. return %s%02d % (date, inc) That's it. Ciao, Marc 'BlackJack' Rintsch Ah return %s%02d % (date, inc) This piece is what I was missing in my original design. I couldn't figure out hot to take and integer and force it to my double digit. i.e. 01 instead of 1. Which is why I was using strings to make that happen. (obviously incorrectly). Thanks Could you explain what assert does in the if statement. I am assuming if the first two conditions are not met, it will hit assert false and exit the program? -- http://mail.python.org/mailman/listinfo/python-list
Re: Beginner: Data type conversion question
flagg wrote: If rdate.serial is already a string, as name would imply, the str() call is pointless. If not, can you get inc as int more directly? ... Actually when i run a type(serial) on that variable it returns a long Then inc = serial % 100 is 'more directly'. which i am not sure why dnspython uses a long variable to store the serial. Perhaps a holdever from C code where long is necessary to dependably hold counts with 8 decimal digits. -- http://mail.python.org/mailman/listinfo/python-list
Re: Beginner: Data type conversion question
On Thu, Jan 15, 2009 at 9:09 PM, flagg ianand0...@gmail.com wrote: I am still fairly new to python and programming in general. My question is regarding data conversion, I am working on a script that will edit dns zone files, one of the functions i wrote handles updating the serial number. Our zone files use the date as the first part of the serial and a two digit integer as the last two. i.e. 2009011501. The next update would be 2009011502, etc Here is the function I wrote, I am using dnspython for reading in zone files as Zone objects. Because dnspython's built-in serial updater will not work with how we format our serial's, I have to re-write it. def checkSerial(): Checks the current 'date' portion of the serial number and checks the current 'counter'(the two digit number at the end of the serial number), then returns a complete new serial currentDate = time.strftime(%Y%m%d, time.localtime()) for (name, ttl, rdata) in zone.iterate_rdatas(SOA): date = str(rdata.serial)[0:8] inc = str(rdata.serial)[8:10] if date == currentDate: int(inc) + 1 The previous line is pointless. It's like having '4+4' as a statement on its own line. It calculates a value but doesn't change any state or even use the value. Perhaps you instead meant?: inc = int(inc) + 1 Cheers, Chris -- Follow the path of the Iguana... http://rebertia.com -- http://mail.python.org/mailman/listinfo/python-list
Re: Beginner: Data type conversion question
On Jan 15, 9:16 pm, Chris Rebert c...@rebertia.com wrote: On Thu, Jan 15, 2009 at 9:09 PM, flagg ianand0...@gmail.com wrote: I am still fairly new to python and programming in general. My question is regarding data conversion, I am working on a script that will edit dns zone files, one of the functions i wrote handles updating the serial number. Our zone files use the date as the first part of the serial and a two digit integer as the last two. i.e. 2009011501. The next update would be 2009011502, etc Here is the function I wrote, I am using dnspython for reading in zone files as Zone objects. Because dnspython's built-in serial updater will not work with how we format our serial's, I have to re-write it. def checkSerial(): Checks the current 'date' portion of the serial number and checks the current 'counter'(the two digit number at the end of the serial number), then returns a complete new serial currentDate = time.strftime(%Y%m%d, time.localtime()) for (name, ttl, rdata) in zone.iterate_rdatas(SOA): date = str(rdata.serial)[0:8] inc = str(rdata.serial)[8:10] if date == currentDate: int(inc) + 1 The previous line is pointless. It's like having '4+4' as a statement on its own line. It calculates a value but doesn't change any state or even use the value. Perhaps you instead meant?: inc = int(inc) + 1 Cheers, Chris -- Follow the path of the Iguana...http://rebertia.com Ah thank you. Oversight on my part. That explains why that if statement never incremented the counter correctly. Anything odd about how I'm converting back and forth between different data types as often as I am? Is that common practice is normal programming? (forgive the beginner questions) -- http://mail.python.org/mailman/listinfo/python-list
Re: Beginner: Data type conversion question
flagg wrote: I am still fairly new to python and programming in general. My question is regarding data conversion, I am working on a script that will edit dns zone files, one of the functions i wrote handles updating the serial number. Our zone files use the date as the first part of the serial and a two digit integer as the last two. i.e. 2009011501. The next update would be 2009011502, etc Here is the function I wrote, I am using dnspython for reading in zone files as Zone objects. Because dnspython's built-in serial updater will not work with how we format our serial's, I have to re-write it. def checkSerial(): Checks the current 'date' portion of the serial number and checks the current 'counter'(the two digit number at the end of the serial number), then returns a complete new serial currentDate = time.strftime(%Y%m%d, time.localtime()) for (name, ttl, rdata) in zone.iterate_rdatas(SOA): date = str(rdata.serial)[0:8] inc = str(rdata.serial)[8:10] If rdate.serial is already a string, as name would imply, the str() call is pointless. If not, can you get inc as int more directly? if date == currentDate: int(inc) + 1 print inc newInc = str(inc).zfill(2) serial = date + newInc print date is the same return serial elif date currentDate: newInc = 01.zfill(2) serial = currentDate + newInc print date is different return serial Through all of this I am doing a lot of data type conversion. string - integer, integer back to string, etc. Is this an efficient way of handling this? I have to perform basic addition on the inc variable, but also need to expose that value as a string. What I have above does work, but I can't help but think there is a more efficient way. I guess I am not used to data types being converted so easily. Other than that, you are perhaps worrying too much, even if code could be squeezed more. The idea that every object knows how to convert itself to a string representation is basic to Python. tjr -- http://mail.python.org/mailman/listinfo/python-list
Re: Beginner: Data type conversion question
On Thu, 15 Jan 2009 21:09:43 -0800, flagg wrote: def checkSerial(): Checks the current 'date' portion of the serial number and checks the current 'counter'(the two digit number at the end of the serial number), then returns a complete new serial currentDate = time.strftime(%Y%m%d, time.localtime()) The format string can be written as *one* string literal instead of three: %Y%m%d. for (name, ttl, rdata) in zone.iterate_rdatas(SOA): date = str(rdata.serial)[0:8] inc = str(rdata.serial)[8:10] Here you are converting `rdata.serial` twice. tmp = str(rdata.serial) date = tmp[0:8] inc = int(tmp[8:10]) As `inc` is conceptually a number, you should do the conversion here and treat it as number from now on. if date == currentDate: int(inc) + 1 print inc newInc = str(inc).zfill(2) serial = date + newInc print date is the same return serial elif date currentDate: newInc = 01.zfill(2) serial = currentDate + newInc print date is different return serial Both branches do almost the same. You should try to avoid such code duplication. if date == currentDate: inc += 1 elif date currentDate: inc = 1 else: assert False # Should never happen. return %s%02d % (date, inc) That's it. Ciao, Marc 'BlackJack' Rintsch -- http://mail.python.org/mailman/listinfo/python-list
