[Tutor] read line x from a file

[Kent Johnson]

Max Noel wrote:
> 
> On Jan 22, 2005, at 13:53, Kent Johnson wrote:
> 
>> That is the simplest solution. If your file gets bigger and you don't 
>> want to read it all at once, you can use enumerate to iterate the 
>> lines and pick out the one you want:
>>
>> f = open(...)
>> for i, line in enumerate(f):
>>   if i==targetLine:
>>     print line # or whatever
>>     break
>> f.close()
> 
> 
>     Of course, to do that, you must know the number of lines in the file 
> beforehand. If you're running a UNIX system (Linux, OS X, *BSD...), 
> that's easily done by calling the command "wc -l <filename>" (use 
> os.popen to do that).

enumerate() takes an iterator as an argument. The above program will read one line of the file at a 
time; when the target line is reached it will be printed. The file will only be read up until the 
target line.

Or maybe you mean that to select a target line you have to know how many lines are in the file? Yes, 
I suppose you do...the OP wasn't very specific about how the line is selected...in that case 
readlines() might be the simplest thing to do.

PS random.choice() might be handy here.

Kent

> 
> -- Max
> maxnoel_fr at yahoo dot fr -- ICQ #85274019
> "Look at you hacker... A pathetic creature of meat and bone, panting and 
> sweating as you run through my corridors... How can you challenge a 
> perfect, immortal machine?"
> 
>