> I want to be able to replace a single line in a large text file
> (several hundred MB). Using the cookbook's method (below) works but I
> think the replace fxn chokes on such a large chunk of text. For now, I
> simply want to replace the 1st line (CSV header) in the file but I'd
> also like to know a more general solution for any line in the file.
> There's got a be quick and dirty (and cheap) way to do this... any
> help?
>
> Cookbook's method:
> output_file.write(input_file.read().replace(stext, rtext))
The read() method slurps the entire file into memory...bad in the
case you describe.
What you want is to process the file as a stream:
first = True
out = file("out.txt", "w")
for line in file("foo.txt"):
if first:
out.write(line.replace(stext, rtext))
first = False
else:
out.write(line)
If you're using an older version of Python, I don't know if
file() returns an iterator, so you might have to do something like
for line in file("foo.txt").xreadlines():
which I understand is the same sort of thing. I don't know the
history of this too well--others on the list are likely better
versed in such peculariaties.
Or, for those *nix wonks in the crowd (self included), sed will
do the trick nicely:
sed '1s/stext/rtext/' foo.txt > out.txt
Just a few ideas,
-tkc
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