iterating over lines in a file

[Daley, Mark W]

Isn't the argument for readlines() a memory size, as in 512 bytes?  If so,
it is possible to have 3509 lines that are <= 512 bytes.

Just my two cents...

- Mark

-----Original Message-----
From: cjc26 at nospam.cornell.edu [mailto:cjc26 at nospam.cornell.edu]
Sent: Friday, July 21, 2000 1:32 PM
To: python-list at python.org
Subject: Re: iterating over lines in a file


* David Bolen <db3l at fitlinxx.com> menulis:
| 
| > readlines() has an optional argument which specifies the approximate
| > number of bytes to read in at a time, rather than the entire file.
| > So something like
| > 
| > for line in file.readlines(8192):
| >     # process line
| > 
| > would only use about 8k of memory.
| 
| And only fully process files less than 8K in size.  The call to
| file.readlines(8192) returns the list of lines contained within the
| first 8K of the file (approximately), and that's all the 'for' is
| going to iterate over.  You have to repeatedly call file.readlines()
| again to keep reading the file, which puts you pretty much back in the
| original readline() mode, just with bigger chunks.

That doesn't seem to be true--readlines() reads the whole file whether
you specify a size argument or not.  For example:

>>> f=open("file.txt")
>>> size=0  
>>> for line in f.readlines():
...     size=size+len(line)
... 
>>> size
3509
>>> f.close()
>>> f=open("file.txt")
>>> size=0
>>> for line in f.readlines(512):
...     size=size+len(line)
... 
>>> size
3509


-- 
cliff crawford    -><-    http://www.people.cornell.edu/pages/cjc26/
                          Synaesthesia now!            icq 68165166