How to remove empty lines with re?

[ted]

I'm having trouble using the re module to remove empty lines in a file.

Here's what I thought would work, but it doesn't:

import re
f = open("old_site/index.html")
for line in f:
line = re.sub(r'^\s+$| \n', '', line)
print line

Also, when I try to remove some HTML tags, I get even more empty lines:

import re
f = open("old_site/index.html")
for line in f:
line = re.sub('<.*?>', '', line)
line = re.sub(r'^\s+$| \n', '', line)
print line

I don't know what I'm doing. Any help appreciated.

TIA,
Ted

[Tim Haynes]

Re: How to remove empty lines with re?

"ted" <tedNOSPAM94107 @yahoo.com> writes:
[color=blue]
> f = open("old_site/index.html")
> for line in f:
> line = re.sub(r'^\s+$| \n', '', line) # }
> print line # }[/color]


If you will set a variable to an empty string and then print it, you will
get an empty line printed ;)

~Tim
--
Product Development Consultant
OpenLink Software
Tel: +44 (0) 20 8681 7701
Web: <http://www.openlinksw. com>
Universal Data Access & Data Integration Technology Providers

[Peter Otten]

Re: How to remove empty lines with re?

ted wrote:
[color=blue]
> I'm having trouble using the re module to remove empty lines in a file.
>
> Here's what I thought would work, but it doesn't:
>
> import re
> f = open("old_site/index.html")
> for line in f:
> line = re.sub(r'^\s+$| \n', '', line)
> print line[/color]

Try:

import sys
for line in f:
if line.strip():
sys.stdout.writ e(line)

Background: lines read from the file keep their trailing "\n", a second
newline is inserted by the print statement.
The strip() method creates a copy of the string with all leading/trailing
whitespace chars removed. All but the empty string evaluate to True in the
if statement.

Peter

[Bror Johansson]

Re: How to remove empty lines with re?


"ted" <tedNOSPAM94107 @yahoo.com> wrote in message
news:vocoudjtp6 vv25@corp.super news.com...[color=blue]
> I'm having trouble using the re module to remove empty lines in a file.
>
> Here's what I thought would work, but it doesn't:
>
> import re
> f = open("old_site/index.html")
> for line in f:
> line = re.sub(r'^\s+$| \n', '', line)
> print line
>[/color]

nonempty = [x for x in f if not x.strip()]

/BJ

[Anand Pillai]

Re: How to remove empty lines with re?

To do this, you need to modify your re to just
this

empty=re.compil e('^$')

This of course looks for a pattern where there is beginning just
after end, ie the line is empty :-)

Here is the complete code.

import re

empty=re.compil e('^$')
for line in open('test.txt' ).readlines():
if empty.match(lin e):
continue
else:
print line,

The comma at the end of the print is to avoid printing another newline,
since the 'readlines()' method gives you the line with a '\n' at the end.

Also dont forget to compile your regexps for efficiency sake.

HTH

-Anand Pillai


"ted" <tedNOSPAM94107 @yahoo.com> wrote in message news:<vocoudjtp 6vv25@corp.supe rnews.com>...[color=blue]
> I'm having trouble using the re module to remove empty lines in a file.
>
> Here's what I thought would work, but it doesn't:
>
> import re
> f = open("old_site/index.html")
> for line in f:
> line = re.sub(r'^\s+$| \n', '', line)
> print line
>
> Also, when I try to remove some HTML tags, I get even more empty lines:
>
> import re
> f = open("old_site/index.html")
> for line in f:
> line = re.sub('<.*?>', '', line)
> line = re.sub(r'^\s+$| \n', '', line)
> print line
>
> I don't know what I'm doing. Any help appreciated.
>
> TIA,
> Ted[/color]

[Anand Pillai]

Re: How to remove empty lines with re?

Errata:

I meant "there is end just after the beginning" of course.

-Anand

"ted" <tedNOSPAM94107 @yahoo.com> wrote in message news:<vocoudjtp 6vv25@corp.supe rnews.com>...[color=blue]
> I'm having trouble using the re module to remove empty lines in a file.
>
> Here's what I thought would work, but it doesn't:
>
> import re
> f = open("old_site/index.html")
> for line in f:
> line = re.sub(r'^\s+$| \n', '', line)
> print line
>
> Also, when I try to remove some HTML tags, I get even more empty lines:
>
> import re
> f = open("old_site/index.html")
> for line in f:
> line = re.sub('<.*?>', '', line)
> line = re.sub(r'^\s+$| \n', '', line)
> print line
>
> I don't know what I'm doing. Any help appreciated.
>
> TIA,
> Ted[/color]

[Klaus Alexander Seistrup]

Re: How to remove empty lines with re?

Anand Pillai wrote:
[color=blue]
> Here is the complete code.
>
> import re
>
> empty=re.compil e('^$')
> for line in open('test.txt' ).readlines():
> if empty.match(lin e):
> continue
> else:
> print line,[/color]

The .readlines() method retains any line terminators, and using the
builtin print will suffix an extra line terminator to every line,
thus effectively producing an empty line for every non-empty line.
You'd want to use e.g. sys.stdout.writ e() instead of print.


// Klaus

--[color=blue]
><> unselfish actions pay back better[/color]

[ted]

Re: How to remove empty lines with re?

Thanks Anand, works great.


"Anand Pillai" <pythonguy@Hotp op.com> wrote in message
news:84fc4588.0 310100849.4546e 804@posting.goo gle.com...[color=blue]
> To do this, you need to modify your re to just
> this
>
> empty=re.compil e('^$')
>
> This of course looks for a pattern where there is beginning just
> after end, ie the line is empty :-)
>
> Here is the complete code.
>
> import re
>
> empty=re.compil e('^$')
> for line in open('test.txt' ).readlines():
> if empty.match(lin e):
> continue
> else:
> print line,
>
> The comma at the end of the print is to avoid printing another newline,
> since the 'readlines()' method gives you the line with a '\n' at the end.
>
> Also dont forget to compile your regexps for efficiency sake.
>
> HTH
>
> -Anand Pillai
>
>
> "ted" <tedNOSPAM94107 @yahoo.com> wrote in message[/color]
news:<vocoudjtp 6vv25@corp.supe rnews.com>...[color=blue][color=green]
> > I'm having trouble using the re module to remove empty lines in a file.
> >
> > Here's what I thought would work, but it doesn't:
> >
> > import re
> > f = open("old_site/index.html")
> > for line in f:
> > line = re.sub(r'^\s+$| \n', '', line)
> > print line
> >
> > Also, when I try to remove some HTML tags, I get even more empty lines:
> >
> > import re
> > f = open("old_site/index.html")
> > for line in f:
> > line = re.sub('<.*?>', '', line)
> > line = re.sub(r'^\s+$| \n', '', line)
> > print line
> >
> > I don't know what I'm doing. Any help appreciated.
> >
> > TIA,
> > Ted[/color][/color]

[Anand Pillai]

Re: How to remove empty lines with re?

You probably did not read my posting completely.

I have added a comma after the print statement and mentioned
a comment specifically on this.

The 'print line,' statement with a comma after it does not print
a newline which you also call as line terminator whereas
the 'print' without a comma at the end does just that.

No wonder python sometimes feels like high-level psuedocode ;-)
It has that ultra intuitive feel for most of its tricks.

In this case, the comma is usually put when you have more than
one item to print, and python puts a newline after all items.
So it very intuitively follows that just putting a comma will not
print a newline! It is better than telling the programmer to use
another print function to avoid newlines, which you find in many
other 'un-pythonic' languages.

-Anand

Klaus Alexander Seistrup <spam@magneti c-ink.dk> wrote in message news:<3f86e96c-da7dc89b-addc-47d2-82cf-a60a482e6e07@ne ws.szn.dk>...[color=blue]
> Anand Pillai wrote:
>[color=green]
> > Here is the complete code.
> >
> > import re
> >
> > empty=re.compil e('^$')
> > for line in open('test.txt' ).readlines():
> > if empty.match(lin e):
> > continue
> > else:
> > print line,[/color]
>
> The .readlines() method retains any line terminators, and using the
> builtin print will suffix an extra line terminator to every line,
> thus effectively producing an empty line for every non-empty line.
> You'd want to use e.g. sys.stdout.writ e() instead of print.
>
>
> // Klaus[/color]

[Klaus Alexander Seistrup]

Re: How to remove empty lines with re?

Anand Pillai wrote:
[color=blue]
> You probably did not read my posting completely.
>
> I have added a comma after the print statement and mentioned
> a comment specifically on this.[/color]

You are completely right, I missed an important part of your posting.
I didn't know about the comma feature, so thanks for teaching me!

Cheers,

// Klaus

--[color=blue]
><> unselfish actions pay back better[/color]