How to get the previous line in a file?

Qilong Ren qilong_ren at
Fri Mar 16 22:09:23 CET 2007

Hi, Shane,

Thanks for fast reply.

What I used is :
       for line in open(FILE):
           <do stuff>
I don't want to store all lines in a list because sometimes the file is very large. We need to store the value of the previous line in a variable. Is that right? 


----- Original Message ----
From: Shane Geiger <sgeiger at>
To: Qilong Ren <qilong_ren at>
Sent: Friday, March 16, 2007 1:51:09 PM
Subject: Re: How to get the previous line in a file?

lines = open('/tmp/', 

previous_line = 

for line in 

    if "foo" in 

        print "found foo in the current line.  The previous line is:  " 


Qilong Ren wrote:
> Hi,all
> I am new to this list. And I am glade I am here.
> I have a question. I need to do some text processing. I need to read 
> from a file line by line. If some line is met with some condition, the 
> previous line needs some modification. How to get the info of the 
> previous line?
> Thanks!
> Qilong
> ------------------------------------------------------------------------
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Shane Geiger
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National Council on Economic Education
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