Hi,
Thanks for the responses. My book, Beginning Python: From Novice to
Professional(p. 266) says that "sys.stdin is iterable, just like other
files", so I thought I would test it out. However, I don't see how
it is acting similar to a file in my example.
I assume all input is buffered by default, so I'm not sure how it
explains things to say that input from sys.stdin is buffered.
> I typed many lines, but lst contains only one item, as expected. Same as
> your regular file example: the file contains many lines, but only the
> first goes into the list.
Interesting example--not as I expected! But there is a difference in
the two examples isn't there? When you iterate over a file, the whole
file isn't put into an internal buffer first, is it?
> I don't know if this a python or OS thing, but I know that iterating over a
> file is not like applying successive call to readline method. You should try
> to use readline instead.
I've wondered what the differences were. Thanks for bringing that
up. I searched around on google, and PEP 234 has this to say about
that:
------------------------------------
- Files implement a tp_iter slot that is equivalent to
iter(f.readline, ""). This means that we can write
for line in file:
...
as a shorthand for
for line in iter(file.readline, ""):
...
which is equivalent to, but faster than
while 1:
line = file.readline()
if not line:
break
...
...
Because the file iterator uses an internal buffer, mixing this
with other file operations (e.g. file.readline()) doesn't work
right. Also, the following code:
for line in file:
if line == "\n":
break
for line in file:
print line,
doesn't work as you might expect, because the iterator created by
the second for-loop doesn't take the buffer read-ahead by the
first for-loop into account. A correct way to write this is:
it = iter(file)
for line in it:
if line == "\n":
break
for line in
it:
print line,
--------------------------------------------
> You may want to look at a related issue:
> http://www.python.org/sf/1633941
Bad link.
>This should be f = iter(raw_input,"") and this will end in a EOFError
>and stop on blank line. So you need a wrapper
Why a wrapper? This example seems to work without error:
lst = []
f = iter(raw_input, "")
for line in f:
lst.append(line)
print lst
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