[Edu-sig] Teaching about files

Kent Johnson kent37 at tds.net
Sun Nov 7 23:36:14 CET 2004

I'm getting ready to teach about files this week.

I'm not too happy with this chapter in Dawson. He spends quite a lot of 
time on f.read(n) and f.readline(n) and very little on 'for line in f:'.

In several months of answering questions on the Tutor list, I have seen 
many programs whose structure is (or could be) like this:
f = open(...)
for line in f:
   data = line.split() # or some variation of this
   # do something with data

Sometimes the programs are written with readlines(), sometimes it is 
f.read() followed by split('\n'), but it's all the same idea and the 
best way to express it is with 'for line in f:'.

On the other hand, I can't remember any use of f.read(n) on the Tutor 
list at all. And it's hard to imagine why I would use f.readline(n); why 
not just f.readline() and process the line data? (Maybe if lines could 
be gargantuan...)

So my question is, am I missing something here? Is f.read(n) important? 
I want to de-emphasize f.read(n) and ignore f.readline(n), and emphasize 
'for line in f:', with f.read(), f.readline() and f.readlines() also 


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