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Re: How to store a variable when a script is executing for next time execution?

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On 06/06/2013 06:50 AM, Avnesh Shakya wrote:
> hi,
>     I am running a python script and it will create a file name like filename0.0.0 and If I run it again then new file will create one more like filename0.0.1...... my code is-
>
> i = 0

Redundant initialization of i.

> for i in range(1000):
>      try:
>          with open('filename%d.%d.%d.json'%(0,0,i,)): pass
>          continue
>      except IOError:
>          dataFile = file('filename%d.%d.%d.json'%(0,0,i,), 'a+')
>          break
> But It will take more time after creating many files, So i want to store value of last var "i" in a variable

There are no variables once the program ends.  You mean you want to 
store it in the file.  That's known as persistent storage, and in the 
general case you could use pickle or something like that.  But in your 
simple case, the easiest thing would be to simply write the last value 
of i out to a file in the same directory.

Then when your program starts, it opens that extra file and reads in the 
value of i.  And uses that for the starting value in the loop.

  so that when i run my script again then I can use it. for example-
>                   my last created file is filename0.0.27 then it should store 27 in a variable and when i run again then new file should be created 0.0.28 according to last value "27", so that i could save time and it can create file fast..
>
> Please give me suggestion for it.. How is it possible?
> Thanks
>

Incidentally, instead of opening each one, why not check its existence? 
  Should be quicker, and definitely clearer.

Entirely separate suggestion, since I dislike having extra housekeeping 
files that aren't logically necessary, and that might become out of synch :

If you're planning on having the files densely populated (meaning no 
gaps in the numbering), then you could use a binary search to find the 
last one.  Standard algorithm would converge with 10 existence checks if 
you have a limit of 1000 files.

-- 
DaveA

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Thread

How to store a variable when a script is executing for next time execution? Avnesh Shakya <avnesh.nitk@gmail.com> - 2013-06-06 03:50 -0700
  Re: How to store a variable when a script is executing for next time execution? Cameron Simpson <cs@zip.com.au> - 2013-06-06 21:19 +1000
  Re: How to store a variable when a script is executing for next time execution? Avnesh Shakya <avnesh.nitk@gmail.com> - 2013-06-06 17:36 +0530
  Re: How to store a variable when a script is executing for next time execution? Dave Angel <davea@davea.name> - 2013-06-06 08:14 -0400
  Re: How to store a variable when a script is executing for next time execution? Jussi Piitulainen <jpiitula@ling.helsinki.fi> - 2013-06-06 15:46 +0300
  Re: How to store a variable when a script is executing for next time execution? Chris Angelico <rosuav@gmail.com> - 2013-06-07 01:37 +1000
  Re: How to store a variable when a script is executing for next time execution? MRAB <python@mrabarnett.plus.com> - 2013-06-06 16:54 +0100
  Re: How to store a variable when a script is executing for next time execution? Chris Angelico <rosuav@gmail.com> - 2013-06-07 01:56 +1000

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