By using this site, you agree to our updated Privacy Policy and our Terms of Use. Manage your Cookies Settings.
446,341 Members | 1,396 Online
Bytes IT Community
+ Ask a Question
Need help? Post your question and get tips & solutions from a community of 446,341 IT Pros & Developers. It's quick & easy.

help converting some perl code to python

P: n/a
hi
i need help with converting a piece of perl code to python
......
my $start = '\[start\]';
my $file = '\[files\]';
my $end = '\[end\]';
.....

while(<FILE>) #open a file
{
if ( /$start/ .. /$file/ ) { # if line match [start] till
[files]
do something with $_
}
if (/$file/ .. /$end/ )
{
do something with $_
}
}

The file looks something like:

[start]
....
[files]
....
[end]

the problem is the '..' operator in perl. Is there any equivalent in
python?
any suggestions ?
thanks

Nov 4 '05 #1
Share this Question
Share on Google+
4 Replies


P: n/a
ei***********@yahoo.com enlightened us with:
the problem is the '..' operator in perl. Is there any equivalent in
python? any suggestions ?


I have a suggestion: stop assuming we know perl, and explain what this
'..' operator does.

Sybren
--
The problem with the world is stupidity. Not saying there should be a
capital punishment for stupidity, but why don't we just take the
safety labels off of everything and let the problem solve itself?
Frank Zappa
Nov 4 '05 #2

P: n/a
ei***********@yahoo.com wrote:
the problem is the '..' operator in perl. Is there any equivalent in
python?


I can't think of anything with a similar operation, to be honest. I'd
try using while loops which look out for the next section delimiter.

--
Ben Sizer.

Nov 4 '05 #3

P: n/a
ei***********@yahoo.com wrote:
i need help with converting a piece of perl code to python the problem is the '..' operator in perl. Is there any equivalent in
python?


Here is a class that emulates the .. operator:

<code>
import sys
import re

start, files, end = map(re.escape, ["[start]", "[files]", "[end]"])

class Section(object):
def __init__(self, start, end):
self.start = re.compile(start).match
self.end = re.compile(end).match
self.inside = False
def __contains__(self, line):
result = self.inside
if result:
if self.end(line):
self.inside = False
else:
if self.start(line):
result = self.inside = True
return result

first = Section(start, files)
second = Section(files, end)
for line in sys.stdin:
line = line[:-1]
if line in first:
# your code
if line in second:
# your code
</code>

However, the simpler

<code>
#untested
import sys

start, files, end = "[start]", "[files]", "[end]"
keys = set([start, files, end])

key = None
for line in sys.stdin:
line = line[:-1]
if line in keys:
key = line
elif key == start:
# your code
elif key == files:
# your code
</code>

might work even better because 'your code' doesn't get to see the sections'
begin/end markers.

Peter

Nov 4 '05 #4

P: n/a
The '..' operator is the flip-flop operator in perl. (It is rarely
used.) It is exactly the same as the 'range' type operator. It returns
false until the first condition is met, then it returns true until the
last condition met, then it returns false.

You could create a flip-flop with a python closure (t_cond and f_cond
are functions that take a value and return True of False)

def make_flip_flop(t_cond, f_cond):
state = [False]
def flip_flop(val):
if state[0] and f_cond(val):
state[0] = False
elif not state[0] and t_cond(val):
state[0] = True
return state[0]
return flip_flop

Nov 4 '05 #5

This discussion thread is closed

Replies have been disabled for this discussion.