On 18 dec, 13:58, Lie Ryan <lie.1...@gmail.com> wrote: > On 12/18/2011 10:43 PM, Peter Otten wrote: > > > > > > > > > > > nukeymusic wrote: > > >> On 17 dec, 12:20, "Günther Dietrich"<gd.use...@spamfence.net> wrote: > >>> nukeymusic<nukeymu...@gmail.com> wrote: > >>>> I'm trying to calculate the difference in seconds between two > > >>> [...] > > >>>>>> import datetime > >>>>>> date1 = datetime.datetime.strptime("Dec-13-09:47:12", > >>>>>> "%b-%d-%H:%M:%S") date2 = > >>>>>> datetime.datetime.strptime("Dec-13-09:47:39", "%b-%d-%H:%M:%S") delta > >>>>>> = date2 - date1 delta_seconds = (delta.days * 60 * 60 * 24) + > >>>>>> delta.seconds + ((delta.microseconds + 500000) / 1000000) > > >>> For very big time differences you should consider to use the Decimal > >>> arithmetics (standard module Decimal) instead of integer arithmetics > >>> for the last line. > >>> If you are sure, that you don't use fractional seconds, you can omit > >>> the part with 'delta.microseconds'. > > >>> Best regards, > > >>> Günther > >> That can very much Günther, this helped me a lot further, I'm only > >> struggling with one more problem to finish my first python-program. > >> Could you > >> tell me why I can't write to the outputfile as I do in the code > >> below:? > >> #!/usr/bin/python > >> #version 16/12/2011 > >> #Example of testfile > >> #Dec-13-09:46:45 21.4 +4.76442190E-01 8.135530E-06 1.553691E+00 > >> #Dec-13-09:47:12 21.4 +4.76439120E-01 8.135839E-06 1.553726E+00 > >> #Dec-13-09:47:39 21.4 +4.76427260E-01 8.136261E-06 1.553853E+00 > >> import datetime > >> f = open('testfile','r') > >> g = open('outputfile','w') > >> #get line 1 from input file: > >> line1=f.readline() > >> #get first element in line 1: > >> date1=line1.rsplit()[0] > >> #convert first element tot structured date time > >> struct_date1=datetime.datetime.strptime(date1, "%b-%d-%H:%M:%S") > >> for line in f: > >> temp=line.rsplit() > >> delta=datetime.datetime.strptime(temp[0], "%b-%d-%H:%M:%S")- > >> datetime.datetime.strptime(date1, "%b-%d-%H:%M:%S") > >> delta_seconds = (delta.days * 60 * 60 * 24) + delta.seconds + > >> ((delta.microseconds + 500000) / 1000000) > >> temp[0]=delta_seconds > >> #the following line is wrong, but I don't know how to fix it: > >> g.write(temp) > >> #Close files > >> f.close() > >> g.close() > > > The write() method only accepts strings; you have to convert the temp list > > to a string before passing it on. The minimal change: > > > for line in f: > > temp = line.rsplit() > > delta = (datetime.datetime.strptime(temp[0], "%b-%d-%H:%M:%S") > > -datetime.datetime.strptime(date1, "%b-%d-%H:%M:%S")) > > delta_seconds = ((delta.days * 60 * 60 * 24) + delta.seconds > > + ((delta.microseconds + 500000) / 1000000)) > > temp[0] = str(delta_seconds) > > g.write(" ".join(temp) + "\n") > > > Other observations: > > > - you are repeating calculations in the loop that you can do (and did) > > outside. > > > - use four-space indent for better readability > > > - there's no need to use rsplit(); use split() > > > After a few other modifications: > > > import datetime > > > def parse_line(line): > > date, rest = line.split(None, 1) > > date = datetime.datetime.strptime(date, "%b-%d-%H:%M:%S") > > return date, rest > > > with open('testfile','r') as f: > > with open('outputfile','w') as g: > > first_date, first_rest = parse_line(next(f)) > > for line in f: > > cur_date, rest = parse_line(line) > > delta = cur_date - first_date > > delta_seconds = ((delta.days * 60 * 60 * 24) + delta.seconds > > + ((delta.microseconds + 500000) / 1000000)) > > g.write("%s %s" % (delta_seconds, rest)) > > minor improvement, you can do: > > with open('testfile','r') as f, open('outputfile','w') as g: > ... > > instead of the nested with-block. > > Also, you can use `delta.total_seconds()` instead of `delta_seconds = > ((delta.days * 60 * 60 * 24) + delta.seconds + ((delta.microseconds + > 500000) / 1000000))` > > Therefore (untested): > > import datetime > > def parse_line(line): > date, rest = line.split(None, 1) > date = datetime.datetime.strptime(date, "%b-%d-%H:%M:%S") > return date, rest > > with open('testfile','r') as f, open('outputfile','w') as g: > first_date, first_rest = parse_line(next(f)) > for line in f: > cur_date, rest = parse_line(line) > delta = cur_date - first_date > g.write("%s %s" % (int(round(delta.total_seconds())), rest))
thanks to you and all the others for helping me out with my first python-script. I tested your alternatives and they do work. The only minor inconvenience with the scripts is that the output-file misses the first line i.e. the first timestamp should be reset to zero (seconds), but as these log-files are very large, missing one measurement is not too bad best regards nukey -- http://mail.python.org/mailman/listinfo/python-list