[perl-python] 20050126 find replace strings in file

**Haibao Tang** · Jul 18 '05, 08:44 PM

Re: [perl-python] 20050126 find replace strings in file

OK. But please don't die throwing that string, or this post will lose
its educational purpose as it was meant to be.

**takarov2003@yahoo.com** · Jul 18 '05, 08:44 PM

Re: 20050126 find replace strings in file

Xah Lee wrote:[color=blue]
> © # -*- coding: utf-8 -*-
> © # Python
> ©
> © import sys
> ©
> © nn = len(sys.argv)
> ©
> © if not nn==5:
> © print "error: %s search_text replace_text in_file out_file" %
> sys.argv[0]
> © else:
> © stext = sys.argv[1]
> © rtext = sys.argv[2]
> © input = open(sys.argv[3])
> © output = open(sys.argv[4],'w')[/color]

I guess there is no way to check if the file opened fine? What if the
filesystem or file is locked for this user/session. Pretty puny
language if it cannot tell you that it cannot do what you tell it to.[color=blue]
> ©
> © for s in input:
> © output.write(s. replace(stext,r text))
> © output.close()
> © input.close()[/color]

Same for the close. Is there no way check a good close?

[color=blue]
>
> -------------------------
> save this code as find_replace.py
> run it like this:
> python find_replace.py findtext replacetext in_file out_file
>
> the sys.argv is from sys. sys.argv[0] is the program's name itself.
>
> note the idiom
> "for variable_name in file_object"
>
> note that since this code reads each
> line in turn, so huge file is of no-problemo
>
> the code is based from Python
> Cookbook of Alex Martelli & David
> Ascher, page 121
>
> in Python terminal, type help() then
> 'FILES' and or 'sys'
> for reference.
>
> try to modify this file for your
> needs.
> --------------------------------------
> In perl, similar code can be achieved.
> the following code illustrates.
>
> if (scalar @ARGV != 4) {die "Wrong arg! Unix BNF: $0 <sstr> <rstr>
> <file id1> <file id2>\n"}
> $stext=$ARGV[0];
> $rtext=$ARGV[1];
> $infile = $ARGV[2];
> $outfile = $ARGV[3];
> open(F1, "<$infile") or die "Perl fucked up. Reason: $!";
> open(F2, ">$outfile" ) or die "Perl fucked up. Reason: $!";[/color]

In 7 years of perl programming, I have never seen an open error that
had anything to do with perl processing. Normally, if I get an error,
the file does not exist, or has permissions set so that the current
user/session is not allowed to open the file.
[color=blue]
> while ($line = <F1>) {
> chomp($line);
> $line =~ s/$stext/$rtext/g;
> print F2 "$line\n";
> }
> close(F1) or die "Perl fucked up. Reason: $!";
> close(F2) or die "Perl fucked up. Reason: $!";[/color]

Same here. Never seen Perl fuck up on closing a file. Usually
something in the OS or file system that does it.[color=blue]
> Xah
> xah@xahlee.org
> http://xahlee.org/PageTwo_dir/more.html[/color]

**Dan Perl** · Jul 18 '05, 08:44 PM

Re: 20050126 find replace strings in file

<takarov2003@ya hoo.com> wrote in message
news:1106776836 .679242.167880@ c13g2000cwb.goo glegroups.com.. .[color=blue]
> I guess there is no way to check if the file opened fine? What if the
> filesystem or file is locked for this user/session. Pretty puny
> language if it cannot tell you that it cannot do what you tell it to.
> ..........
> Same for the close. Is there no way check a good close?[/color]

An exception (IOError) is raised when a file operation fails. The open()
and and close() statements should be enclosed in a try-except statement.

Please, take Xah Lee's postings with more than just a grain of salt. As a
matter of fact, you are better off ignoring them than trying to learn from
them. He is an egomaniac who is learning python and who thinks that he can
already teach others. Personally I doubt he will ever learn python well
enough to teach others. Just look at his English. He has a similar list
with a-word-a-day just like the perl-python a-lesson-a-day and he seems
indeed to know a lot of words. But his grammar is horrendous (there's a
word for you, Xah Lee!). And according to his own website he's been living
in North America for more than 15 years! English is a second language for
me too but you won't see me writing something like "this groups is for
Perlers who wants to learn Python".

It may be unfair to pick on his English, but it is the best way I can make
the point to someone who does not know python that Xah Lee does not know
what he's talking about. I find Xah Lee annoying and I could just ignore
him, but I am concerned that some people may actually take his statements
seriously and learn from them. I can't imagine why or how, but there are
actually 26 members in the perl-python Yahoo! group who have registered to
get these bogus lessons sent to them daily!

Dan

**Ala Qumsieh** · Jul 18 '05, 08:44 PM

Re: 20050126 find replace strings in file

takarov2003@yah oo.com wrote:
[color=blue]
> Xah Lee wrote:[color=green]
>>close(F1) or die "Perl fucked up. Reason: $!";
>>close(F2) or die "Perl fucked up. Reason: $!";[/color]
>
>
> Same here. Never seen Perl fuck up on closing a file. Usually
> something in the OS or file system that does it.[/color]

In this case, I'm pretty sure it's the user.

--Ala

**Jürgen Exner** · Jul 18 '05, 08:44 PM

Re: [perl-python] 20050126 find replace strings in file

Xah Lee wrote:
[...][color=blue]
> In perl, similar code can be achieved.
> the following code illustrates.
>
> if (scalar @ARGV != 4)[/color]

Why scalar()? The comparison already creates a scalar context, no need to
enforce it twice.
[color=blue]
> {die "Wrong arg! Unix BNF: $0 <sstr> <rstr>
> <file id1> <file id2>\n"}
> $stext=$ARGV[0];
> $rtext=$ARGV[1];
> $infile = $ARGV[2];
> $outfile = $ARGV[3];[/color]

Ouch, how ugly. What's wrong with a simple
my ($one, $two, $three, $four) = @ARGV;

or the standard way using shift
for ($one, $two, $three, $four) {
$_ = shift;
}
[color=blue]
> open(F1, "<$infile") or die "Perl fucked up. Reason: $!";
> open(F2, ">$outfile" ) or die "Perl fucked up. Reason: $!";[/color]

Really? Usually it's either the OS or the user (disk full, no write
permissions, wrong file name, ...)
[color=blue]
> while ($line = <F1>) {[/color]

Why $line? It doesn't serve any useful purpose here.
[color=blue]
> chomp($line);[/color]

Why chomp()? It doesn't serve any useful purpose here.
[color=blue]
> $line =~ s/$stext/$rtext/g;[/color]

If you would not have used $line above then you would not need the binding
here.
[color=blue]
> print F2 "$line\n";[/color]

If you would not have chomped the line above then you would not need to add
the newline back here. A simpler
print F2 $_;
would have sufficed
[color=blue]
> }
> close(F1) or die "Perl fucked up. Reason: $!";
> close(F2) or die "Perl fucked up. Reason: $!";[/color]

I find this highly unlikely. If at all then the OS failed to complete the
close.

jue

**Eric Schwartz** · Jul 18 '05, 08:45 PM

Re: [perl-python] 20050126 find replace strings in file

To follow up on Jurgen Exner's critique, I present Xah Lee's version, and
then my rewritten version.

"Xah Lee" <xah@xahlee.org > writes:[color=blue]
> if (scalar @ARGV != 4) {die "Wrong arg! Unix BNF: $0 <sstr> <rstr>
> <file id1> <file id2>\n"}
> $stext=$ARGV[0];
> $rtext=$ARGV[1];
> $infile = $ARGV[2];
> $outfile = $ARGV[3];
> open(F1, "<$infile") or die "Perl fucked up. Reason: $!";
> open(F2, ">$outfile" ) or die "Perl fucked up. Reason: $!";
> while ($line = <F1>) {
> chomp($line);
> $line =~ s/$stext/$rtext/g;
> print F2 "$line\n";
> }
> close(F1) or die "Perl fucked up. Reason: $!";
> close(F2) or die "Perl fucked up. Reason: $!";[/color]

#!/usr/bin/perl
use warnings;
use strict;

if (@ARGV != 4) {
die "Wrong arg! Unix BNF: $0 <sstr> <rstr> <file id1> <file id2>"
}
my ($stext, $rtext, $infile, $outfile) = @ARGV;

open my $infh, '<', $infile
or die "Error opening input file [$infile]: $!";
open my $outfh, '>', $outfile
or die "Error opening output file [$outfile]: $!";

while(<$infh>) {
s/$stext/$rtext/g;
print { $outfh } $_;
}
close($infh) or die "Error closing input file [$infile]: $!";
close($outfh) or die "Error closing output file [$outfile]: $!";

My version takes up more lines, but I don't count whitespace--
whitespace is not expensive, and when used properly adds greatly to
the readability of your program.

I've set followups to the only appropriate group for Mr. Lee's
postings.

-=Eric
--
Come to think of it, there are already a million monkeys on a million
typewriters, and Usenet is NOTHING like Shakespeare.
-- Blair Houghton.

**Tad McClellan** · Jul 18 '05, 08:45 PM

Re: 20050126 find replace strings in file

[ Followup set ]

Dan Perl <danperl@rogers .com> wrote:
[color=blue]
> I can't imagine why or how, but there are
> actually 26 members in the perl-python Yahoo! group who have registered to
> get these bogus lessons sent to them daily![/color]

There is one born every minute.

--
Tad McClellan SGML consulting
tadmc@augustmai l.com Perl programming
Fort Worth, Texas

**kosh** · Jul 18 '05, 08:45 PM

Re: 20050126 find replace strings in file

On Wednesday 26 January 2005 7:13 pm, Tad McClellan wrote:[color=blue]
> [ Followup set ]
>
> Dan Perl <danperl@rogers .com> wrote:[color=green]
> > I can't imagine why or how, but there are
> > actually 26 members in the perl-python Yahoo! group who have registered
> > to get these bogus lessons sent to them daily![/color]
>
> There is one born every minute.
>[/color]

Nah it is daily humor. Just think of it like a joke list. :)

**alex23** · Jul 18 '05, 08:45 PM

Re: 20050126 find replace strings in file

kosh wrote:[color=blue]
> Nah it is daily humor. Just think of it like a joke list. :)[/color]

Or a daily puzzler: how many blatantly stupid things can you find in 5
mins?

[perl-python] 20050126 find replace strings in file

[perl-python] 20050126 find replace strings in file

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