[EMAIL PROTECTED] wrote:
> Hi,
> suppose I am reading lines from a file or stdin.
> I want to just "peek" in to the next line, and if it starts
> with a special character I want to break out of a for loop,
> other wise I want to do readline().
>
> Is there a way to do this?
> for example:
> while 1:
> line=stdin.peek_nextline()
> if not line: break
> if line[0]=="|":
> break:
> else:
> x=stdin.nextline()
> # do something with x
>
> thanks
The itertools approach:
(some preparations)
>>> import itertools
>>> file("tmp.txt", "w").write("""\
... a
... b
... c
... |
... d
... e
... f
... """)
(1) You are only interested in lines after and including the "special" line:
>>> def predicate(line):
... return not line.startswith("|")
...
>>> for line in itertools.dropwhile(predicate, file("tmp.txt")):
... print line,
...
|
d
e
f
(2) You want both the "head" and the "tail", where the tail includes the
"special" line:
>>> lines = iter(file("tmp.txt"))
>>> for line in lines:
... if line.startswith("|"):
... lines = itertools.chain([line], lines)
... break
... print "head", line,
...
head a
head b
head c
>>> for line in lines:
... print "tail", line,
...
tail |
tail d
tail e
tail f
>>>
Peter
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