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Simple looping question...
Ken Seehofkens at sightreader.com
Mon Apr 2 20:53:07 EDT 2001
"David Allen" <mda at idatar.com> says:> In article <mailman.986227337.10718.python-list at python.org>, "Vincent A.> Primavera" <vincent_a_primavera at netzero.net> wrote:>> > Hello,> > In a piece of code similar to this I am trying to read all the linesfrom a> > file but no more. How can I set the "range" of this loop to stop whenit> > reaches the end of the file?> >> > for i in range(???):> > a = fil1.readline()> > print a>> You're going at it from the wrong way around. If> you really want to do it based on the number of lines> in the file, do this:>> lines = fil1.readlines()>> for i in range(0, len(lines)):> print lines[i]>> but better would probably be to do this:>> for line in fil1.readlines():> print line>> IIRC, that way you don't have to have the whole damn> file in memory. Python is smart enough to assign> lines one at a time into 'line' rather than to> create an actual array.>> David Allen>http://opop.nols.com/> ----------------------------------------> Great minds run in great circles.I don't believe you.>>> f = open(r'd:\qp\var\publish\index.html')>>> z = f.readlines()>>> type(z)<type 'list'>It would appear that readlines() returns a list. Thereforethe entire file is read in to create that list before returning.On the other hand, I have written a generator class thatdoes what you are saying. In order for readlines() to besmart, it would have to return a generator instead of a list.- Ken Seehofkseehof at neuralintegrator.comwww.neuralintegrator.com
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