[Python-Dev] Use for enumerate() (original) (raw)

holger krekel pyth@devel.trillke.net
Sat, 27 Apr 2002 12:23:00 +0200

On Sat, Apr 27, 2002 at 12:24:46AM -0400, Tim Peters wrote:

[holger krekel] > measured with your driver script the following code > is about 10-20% faster than 'g2' and it gets close to > > > > Challenge 3: do it faster and with less code. > > def g3(filename, lineno): > if lineno>0: > f = file(filename) > while lineno>0: > read = f.read(1024) > count = read.count('\n') > lineno-=count or lineno > f.close() > if lineno<count:_ _> return read.split('\n')[lineno+count-1] > return '' > > vertically it's one line less but it stretches > a bit horizontally. But it is more portable :-)

What if (the simplest example of what can go wrong) the first line is more than 1024 characters long, and the caller asks for lineno 1?

right. i noticed after sending it that you also need to change lineno-= count or lineno into lineno-= count or read and lineno

and the problem of lines longer>1024 and around the 1024 boundary remains. Solving this probably blows the code by several lines.

But anyway, isn't reading and counting still a faster technique than using readlines() esp. for larger files? 

 holger