On Wed, Aug 22, 2012 at 11:38 AM, William R. Wing (Bill Wing) <w...@mac.com> wrote: > In the middle of a longer program that reads and plots data from a log file, > I have added the following five lines (rtt_data is fully qualified file name): > > wd = open(rtt_data, 'w') > stat = wd.write(str(i)) > stat = wd.writelines(str(x_dates[:i])) > stat = wd.writelines(str(y_rtt[:i])) > wd.close() > > The value of i is unknown before I have read through the input log file, but > is typically in the neighborhood of 2500. x_dates is a list of time stamps > from the date2num method, that is values of the form 734716.72445602, day > number plus decimal fraction of a day. y_rtt is a list of three- or > four-digit floating point numbers. The x_dates and y_rtt lists are complete > and plot correctly using matplotlib. Reading and parsing the input log file > and extracting the data I need is time consuming, so I decided to save the > data for further analysis without the overhead of reading and parsing it > every time. > > Much to my surprise, when I looked at the output file, it only contained 160 > characters. Catting produces: > > StraylightPro:Logs wrw$ cat RTT_monitor.dat > 2354[ 734716.72185185 734716.72233796 734716.72445602 ..., 734737.4440162 > 734737.45097222 734737.45766204][ 240. 28.5 73.3 ..., 28.4 27.4 > 26.4] > > Clearly I'm missing something fundamental about using the writelines method, > and I'm sure it will be a DUH moment for me, but I'd sure appreciate someone > telling me how to get that data all written out. I certainly don't insist on > writelines, but I would like the file to be human-readable. > > Python 2.7.3 > OS-X 10.8 > > Thanks, > Bill > -- > http://mail.python.org/mailman/listinfo/python-list
writelines writes a list of strings to a file. you are using this: > stat = wd.writelines(str(x_dates[:i])) which is the same as my second line below If you use map it will perform the first argument over the list. See if that works for you >>> l = [1,2,3] >>> str(l) '[1, 2, 3]' >>> s = map(str, l) >>> s ['1', '2', '3'] -- Joel Goldstick -- http://mail.python.org/mailman/listinfo/python-list
