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replacing timestamps in file [newbie]

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  replacing timestamps in file [newbie] nukeymusic <nukeymusic@gmail.com> - 2011-12-14 12:32 -0800
    Re: replacing timestamps in file [newbie] Miki Tebeka <miki.tebeka@gmail.com> - 2011-12-14 12:56 -0800
    Re: replacing timestamps in file [newbie] Chris Angelico <rosuav@gmail.com> - 2011-12-15 08:07 +1100

#17234 — replacing timestamps in file [newbie]

I have a file which has the data in the following format:
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
.
.
the first field is a timestamp, I'd like to replace it with the time
in seconds starting from the first one like this:
0 21.4 +4.76442190E-01 8.135530E-06 1.553691E+00
27 21.4 +4.76439120E-01 8.135839E-06 1.553726E+00
54 21.4 +4.76427260E-01 8.136261E-06 1.553853E+00

Is there a function in python to achieve this?

thanks in advance

nukey

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#17235

You can either work with datetime module (see datetime.datetime.strptime) or with the time module (see time.strptime and time.mktime)

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#17237

On Thu, Dec 15, 2011 at 7:32 AM, nukeymusic <nukeymusic@gmail.com> wrote:
> I have a file which has the data in the following format:
> Dec-13-09:46:45 21.4 +4.76442190E-01 8.135530E-06 1.553691E+00
>
> the first field is a timestamp, I'd like to replace it with the time
> in seconds starting from the first one like this:
> 27 21.4 +4.76439120E-01 8.135839E-06 1.553726E+00

You're looking for several things here, all of which Python can do.
I'll give you a few pointers - have a browse of the documentation.

1) Reading a file line-by-line is usually best done with the iterator
idiom. Open your file with the "open()" function, read in any headers,
and then use "for line in inputfile:" to loop over the data.

2) Parse the line into separate pieces using the split() and join()
methods of the string object

3) Use the time.strptime() function to convert the string date into
something more usable

4) Maintain a variable with "previous time" and take the difference each time.

5) Write the modified lines to another file.

Python's pretty good with this sort of job. It won't let you down!

Chris Angelico

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