[Tutor] files

[Alan Gauld]

"Ricardo Aráoz" <ricaraoz at gmail.com> wrote

>>>> In = open(r'E:\MyDir\MyDoc.txt', 'rb')
>>>> Out = open(r'E:\MyDir\MyUpperDoc.txt', 'wb')
>>>> Out.write(In.read().upper())
>>>> In.close()
>>>> Out.close()
>
> Pretty simple program. The question is : If 'In' is a HUGE file, how
> does Python process it?

Exactly as it does for a small file... :-)

> Does it treat it as a stream and passes bytes to
> 'Out' as soon as they are coming in, or does it read the whole file 
> into
> memory and then passes the whole file to 'Out'?

You have told it to do the latter.
read() reads the whole file into a string so

Out.write(In.read().upper())

Is exactly the same as

temp = In.read()
temp = temp.upper()
Out.write(temp)

Just because you put it in one line doesn't chanhge how
Python interprets it.

> If the answer is the first choice I would like to know how to 
> instruct
> Python to do the second choice.

I'm guessing you mean this the other way around?

You can read the file line by line

for line in In:
    Out.write(line.upper())

HTH,


-- 
Alan Gauld
Author of the Learn to Program web site
http://www.freenetpages.co.uk/hp/alan.gauld