Develop Reference

How to Remove Pipe character from a data filed in a pipe delimited file

Experts, i have a simple pipe delimited file from source system which has a free flow text field and for one of the records, i see that "|" character is coming in as part of data. This is breaking my file unevenly and not getting parsed in to correct number of fields. I want to replace the "|" in the data field with a "#".
Record coming in from source system. There are total 9 fields in the file.
OutboundManualCall|H|RTYEHLA HTREDFST|Free"flow|Text|20191029|X|X|X|3456
If you Notice the 4th field - Free"flow|Text , this is complete value from source which has a pipe in it.
i want to change it to- Free"flow#Text and then read the file with a pipe delimiter.
Desired Outcome-
OutboundManualCall|H|RTYEHLA HTREDFST|Free"flow#Text|20191029|X|X|X|3456
I tried few awk/sed combinations, but didn't get the desired output.
Thanks

Since you know there are 9 fields, and the 4th is a problem: take the first 3 fields and the last 5 fields and whatever is left over is the 4th field.
You did tag shell, so here's some bash: I'm sure the python equivalent is close:
line='OutboundManualCall|H|RTYEHLA HTREDFST|Free"flow|Text|20191029|X|X|X|3456'
IFS='|'
read -ra fields <<<"$line"
first3=( "${fields[#]:0:3}" )
last5=( "${fields[#]: -5}" )
tmp=${line#"${first3[*]}$IFS"} # remove the first 3 joined with pipe
field4=${tmp%"$IFS${last5[*]}"} # remove the last 5 joined with pipe
data=( "${first3[#]}" "$field4" "${last5[#]}" )
newline="${first3[*]}$IFS${field4//$IFS/#}$IFS${last5[*]}"
# .......^^^^^^^^^^^^....^^^^^^^^^^^^^^^^^....^^^^^^^^^^^
printf "%s\n" "$line" "$newline"
OutboundManualCall|H|RTYEHLA HTREDFST|Free"flow|Text|20191029|X|X|X|3456
OutboundManualCall|H|RTYEHLA HTREDFST|Free"flow#Text|20191029|X|X|X|3456
with awk, it's simpler: If there are 10 fields, join fields 4 and 5, and shift the rest down one.
echo "$line" | awk '
BEGIN { FS = OFS = "|" }
NF == 10 {
$4 = $4 "#" $5
for (i=5; i<NF; i++)
$i = $(i+1)
NF--
}
1
'
OutboundManualCall|H|RTYEHLA HTREDFST|Free"flow#Text|20191029|X|X|X|3456

You tagged your question with Python so I assume a Python-based answer is acceptable.
I assume not all records in your file have the additional "|" in it, but only some records have the "|" in the free text column.
For a more realistic example, I create an input with some correct records and some erroneous records.
I use StringIO to simulate the file, in your environment read the real file with 'open'.
from io import StringIO
sample = 'OutboundManualCall|H|RTYEHLA HTREDFST|Free"flow|Text|20191029|X|X|X|3456\nOutboundManualCall|J|LALALA HTREDFST|FreeHalalText|20191029|X|X|X|3456\nOutboundManualCall|J|LALALA HTREDFST|FrulaalText|20191029|X|X|X|3456\nOutboundManualCall|H|RTYEHLA HTREDFST|Free"flow|Text|20191029|X|X|X|3456'
infile = StringIO(sample)
outfile = StringIO()
for line in infile.readlines():
cols = line.split("|")
if len(cols) > 9:
print(f"bad colum {cols[3:5]}")
line = "|".join(cols[:3]) + "#".join(cols[3:5]) + "|".join(cols[5:])
outfile.write(line)
print("Corrected file:")
print(outfile.getvalue())
Results in:
> bad colum ['Free"flow', 'Text']
> bad colum ['Free"flow', 'Text']
> Corrected file:
> OutboundManualCall|H|RTYEHLA HTREDFSTFree"flow#Text20191029|X|X|X|3456
> OutboundManualCall|J|LALALA HTREDFST|FreeHalalText|20191029|X|X|X|3456
> OutboundManualCall|J|LALALA HTREDFST|FrulaalText|20191029|X|X|X|3456
> OutboundManualCall|H|RTYEHLA HTREDFSTFree"flow#Text20191029|X|X|X|3456

Split csv file vertically using command line

Is it possible to split a csv file, vertically, into multiple files? I know we can split single large files into smaller files with no of rows mentioned using the command line. I have csv files in which columns are repeating after certain column no and I want to split that file column-wise.Is that possible with the command line, If not then how can we do it with python?
For Eg.
consider above sample in which site and address present multiple times vertically, I want to create 3 different csv files containing single site and single address
Any help would be highly appreciated,
Thanks

Assuming your input files is named ~/Downloads/sites.csv and looks like this:
Google,google.com,Google,google.com,Google,google.com
MS,microsoft.com,MS,microsoft.com,MS,microsoft.com
Apple,apple.com,Apple,apple.com,Apple,apple.com
You can use cut to create 3 files, each containing one pair of company/site:
cut -d "," -f 1-2 < ~/Downloads/sites.csv > file1.csv
cut -d "," -f 3-4 < ~/Downloads/sites.csv > file2.csv
cut -d "," -f 5-6 < ~/Downloads/sites.csv > file3.csv
Explanation:
For the cut command, we declare the comma (,) as a separator, which splits every line into a set for 'fields'.
We then specify for each output file, which fields we want to be included.
HTH!

If the site-address pairs are regularly repeated, how about:
awk '{
n = split($0, ary, ",");
for (i = 1; i <= n; i += 2) {
j = (i + 1) / 2;
print ary[i] "," ary[i+1] >> "file" j ".csv";
}
}' input.csv

The following script produces what you want (based on the SO answer adjusted for your needs: number of columns, field separator). It splits the original file vertically into 2 column chunks (note n=2) and creates 3 different files (tmp.examples.1, tmp.examples.2, tmp.examples.3 or whatever you specify for the f variable):
awk -F "," -v f="tmp.examples" '{for (i=1; i<=NF; i++) printf (i%n==0||i==NF)?$i RS:$i FS > f "." int((i-1)/n+1) }' n=2 example.txt
If your example.txt file has the subsequent data:
site,address,site,address,site,address
Google,google.com,MS,microsoft.com,Apple,apple.com

Combine lines with matching keys

I have a text file with the following structure
ID,operator,a,b,c,d,true
WCBP12236,J1,75.7,80.6,65.9,83.2,82.1
WCBP12236,J2,76.3,79.6,61.7,81.9,82.1
WCBP12236,S1,77.2,81.5,69.4,84.1,82.1
WCBP12236,S2,68.0,68.0,53.2,68.5,82.1
WCBP12234,J1,63.7,67.7,72.2,71.6,75.3
WCBP12234,J2,68.6,68.4,41.4,68.9,75.3
WCBP12234,S1,81.8,82.7,67.0,87.5,75.3
WCBP12234,S2,66.6,67.9,53.0,70.7,75.3
WCBP12238,J1,78.6,79.0,56.2,82.1,84.1
WCBP12239,J2,66.6,72.9,79.5,76.6,82.1
WCBP12239,S1,86.6,87.8,23.0,23.0,82.1
WCBP12239,S2,86.0,86.9,62.3,89.7,82.1
WCBP12239,J1,70.9,71.3,66.0,73.7,82.1
WCBP12238,J2,75.1,75.2,54.3,76.4,84.1
WCBP12238,S1,65.9,66.0,40.2,66.5,84.1
WCBP12238,S2,72.7,73.2,52.6,73.9,84.1
Each ID corresponds to a dataset which is analysed by an operator several times. i.e J1 and J2 are the first and second attempt by operator J. The measures a, b, c and d use 4 slightly different algorithms to measure a value whose true value lies in the column true
What I would like to do is to create 3 new text files comparing the results for J1 vs J2, S1 vs S2 and J1 vs S1. Example output for J1 vs J2:
ID,operator,a1,a2,b1,b2,c1,c2,d1,d2,true
WCBP12236,75.7,76.3,80.6,79.6,65.9,61.7,83.2,81.9,82.1
WCBP12234,63.7,68.6,67.7,68.4,72.2,41.4,71.6,68.9,75.3
where a1 is measurement a for J1, etc.
Another example is for S1 vs S2:
ID,operator,a1,a2,b1,b2,c1,c2,d1,d2,true
WCBP12236,77.2,68.0,81.5,68.0,69.4,53.2,84.1,68.5,82.1
WCBP12234,81.8,66.6,82.7,67.9,67.0,53,87.5,70.7,75.3
The IDs will not be in alphanumerical order nor will the operators be clustered for the same ID. I'm not certain how best to approach this task - using linux tools or a scripting language like perl/python.
My initial attempt using linux quickly hit a brick wall
First find all unique IDs (sorted)
awk -F, '/^WCBP/ {print $1}' file | uniq | sort -k 1.5n > unique_ids
Loop through these IDs and sort J1, J2:
foreach i (`more unique_ids`)
grep $i test.txt | egrep 'J[1-2]' | sort -t',' -k2
end
This gives me the data sorted
WCBP12234,J1,63.7,67.7,72.2,71.6,75.3
WCBP12234,J2,68.6,68.4,41.4,68.9,80.4
WCBP12236,J1,75.7,80.6,65.9,83.2,82.1
WCBP12236,J2,76.3,79.6,61.7,81.9,82.1
WCBP12238,J1,78.6,79.0,56.2,82.1,82.1
WCBP12238,J2,75.1,75.2,54.3,76.4,82.1
WCBP12239,J1,70.9,71.3,66.0,73.7,75.3
WCBP12239,J2,66.6,72.9,79.5,76.6,75.3
I'm not sure how to rearrange this data to get the desired structure. I tried adding an additional pipe to awk in the foreach loop awk 'BEGIN {RS="\n\n"} {print $1, $3,$10,$4,$11,$5,$12,$6,$13,$7}'
Any ideas? I'm sure this can be done in a less cumbersome manner using awk, although it may be better using a proper scripting language.

You can use the Perl csv module Text::CSV to extract the fields, and then store them in a hash, where ID is the main key, the second field is the secondary key and all the fields are stored as the value. It should then be trivial to do whatever comparisons you want. If you want to retain the original order of your lines, you can use an array inside the first loop.
use strict;
use warnings;
use Text::CSV;
my %data;
my $csv = Text::CSV->new({
binary => 1, # safety precaution
eol => $/, # important when using $csv->print()
});
while ( my $row = $csv->getline(*ARGV) ) {
my ($id, $J) = #$row; # first two fields
$data{$id}{$J} = $row; # store line
}

Python Way:
import os,sys, re, itertools
info=["WCBP12236,J1,75.7,80.6,65.9,83.2,82.1",
"WCBP12236,J2,76.3,79.6,61.7,81.9,82.1",
"WCBP12236,S1,77.2,81.5,69.4,84.1,82.1",
"WCBP12236,S2,68.0,68.0,53.2,68.5,82.1",
"WCBP12234,J1,63.7,67.7,72.2,71.6,75.3",
"WCBP12234,J2,68.6,68.4,41.4,68.9,80.4",
"WCBP12234,S1,81.8,82.7,67.0,87.5,75.3",
"WCBP12234,S2,66.6,67.9,53.0,70.7,72.7",
"WCBP12238,J1,78.6,79.0,56.2,82.1,82.1",
"WCBP12239,J2,66.6,72.9,79.5,76.6,75.3",
"WCBP12239,S1,86.6,87.8,23.0,23.0,82.1",
"WCBP12239,S2,86.0,86.9,62.3,89.7,82.1",
"WCBP12239,J1,70.9,71.3,66.0,73.7,75.3",
"WCBP12238,J2,75.1,75.2,54.3,76.4,82.1",
"WCBP12238,S1,65.9,66.0,40.2,66.5,80.4",
"WCBP12238,S2,72.7,73.2,52.6,73.9,72.7" ]
def extract_data(operator_1, operator_2):
operator_index=1
id_index=0
data={}
result=[]
ret=[]
for line in info:
conv_list=line.split(",")
if len(conv_list) > operator_index and ((operator_1.strip().upper() == conv_list[operator_index].strip().upper()) or (operator_2.strip().upper() == conv_list[operator_index].strip().upper()) ):
if data.has_key(conv_list[id_index]):
iters = [iter(conv_list[int(operator_index)+1:]), iter(data[conv_list[id_index]])]
data[conv_list[id_index]]=list(it.next() for it in itertools.cycle(iters))
continue
data[conv_list[id_index]]=conv_list[int(operator_index)+1:]
return data
ret=extract_data("j1", "s2")
print ret
O/P:
{'WCBP12239': ['70.9', '86.0', '71.3', '86.9', '66.0', '62.3', '73.7', '89.7', '75.3', '82.1'], 'WCBP12238': ['72.7', '78.6', '73.2', '79.0', '52.6', '56.2', '73.9', '82.1', '72.7', '82.1'], 'WCBP12234': ['66.6', '63.7', '67.9', '67.7', '53.0', '72.2', '70.7', '71.6', '72.7', '75.3'], 'WCBP12236': ['68.0', '75.7', '68.0', '80.6', '53.2', '65.9', '68.5', '83.2', '82.1', '82.1']}

I didn't use Text::CSV like TLP did. If you needed to you could but for this example, I thought since there were no embedded commas in the fields, I did a simple split on ','. Also, the true fields from both operators are listed (instead of just 1) as I thought the special case of the last value complicates the solution.
#!/usr/bin/perl
use strict;
use warnings;
use List::MoreUtils qw/ mesh /;
my %data;
while (<DATA>) {
chomp;
my ($id, $op, #vals) = split /,/;
$data{$id}{$op} = \#vals;
}
my #ops = ([qw/J1 J2/], [qw/S1 S2/], [qw/J1 S1/]);
for my $id (sort keys %data) {
for my $comb (#ops) {
open my $fh, ">>", "#$comb.txt" or die $!;
my $a1 = $data{$id}{ $comb->[0] };
my $a2 = $data{$id}{ $comb->[1] };
print $fh join(",", $id, mesh(#$a1, #$a2)), "\n";
close $fh or die $!;
}
}
__DATA__
WCBP12236,J1,75.7,80.6,65.9,83.2,82.1
WCBP12236,J2,76.3,79.6,61.7,81.9,82.1
WCBP12236,S1,77.2,81.5,69.4,84.1,82.1
WCBP12236,S2,68.0,68.0,53.2,68.5,82.1
WCBP12234,J1,63.7,67.7,72.2,71.6,75.3
WCBP12234,J2,68.6,68.4,41.4,68.9,75.3
WCBP12234,S1,81.8,82.7,67.0,87.5,75.3
WCBP12234,S2,66.6,67.9,53.0,70.7,75.3
WCBP12239,J1,78.6,79.0,56.2,82.1,82.1
WCBP12239,J2,66.6,72.9,79.5,76.6,82.1
WCBP12239,S1,86.6,87.8,23.0,23.0,82.1
WCBP12239,S2,86.0,86.9,62.3,89.7,82.1
WCBP12238,J1,70.9,71.3,66.0,73.7,84.1
WCBP12238,J2,75.1,75.2,54.3,76.4,84.1
WCBP12238,S1,65.9,66.0,40.2,66.5,84.1
WCBP12238,S2,72.7,73.2,52.6,73.9,84.1
The output files produced are below
J1 J2.txt
WCBP12234,63.7,68.6,67.7,68.4,72.2,41.4,71.6,68.9,75.3,75.3
WCBP12236,75.7,76.3,80.6,79.6,65.9,61.7,83.2,81.9,82.1,82.1
WCBP12238,70.9,75.1,71.3,75.2,66.0,54.3,73.7,76.4,84.1,84.1
WCBP12239,78.6,66.6,79.0,72.9,56.2,79.5,82.1,76.6,82.1,82.1
S1 S2.txt
WCBP12234,81.8,66.6,82.7,67.9,67.0,53.0,87.5,70.7,75.3,75.3
WCBP12236,77.2,68.0,81.5,68.0,69.4,53.2,84.1,68.5,82.1,82.1
WCBP12238,65.9,72.7,66.0,73.2,40.2,52.6,66.5,73.9,84.1,84.1
WCBP12239,86.6,86.0,87.8,86.9,23.0,62.3,23.0,89.7,82.1,82.1
J1 S1.txt
WCBP12234,63.7,81.8,67.7,82.7,72.2,67.0,71.6,87.5,75.3,75.3
WCBP12236,75.7,77.2,80.6,81.5,65.9,69.4,83.2,84.1,82.1,82.1
WCBP12238,70.9,65.9,71.3,66.0,66.0,40.2,73.7,66.5,84.1,84.1
WCBP12239,78.6,86.6,79.0,87.8,56.2,23.0,82.1,23.0,82.1,82.1
Update: To get only 1 true value, the for loop could be written like this:
for my $id (sort keys %data) {
for my $comb (#ops) {
local $" = '';
open my $fh, ">>", "#$comb.txt" or die $!;
my $a1 = $data{$id}{ $comb->[0] };
my $a2 = $data{$id}{ $comb->[1] };
pop #$a2;
my #mesh = grep defined, mesh(#$a1, #$a2);
print $fh join(",", $id, #mesh), "\n";
close $fh or die $!;
}
}
Update: Added 'defined' for test in grep expr. as it is the proper way (instead of just testing '$_', which possibly could be 0 and wrongly excluded for the list by grep).

Any problem that awk or sed can solve, there is no doubt that python, perl, java, go, c++, c can too. However, it is not necessary to write a complete program in any of them.
Use awk in one liner
VERSION 1
For the most use cases, I think the VERSION 1 is good enough.
tail -n +2 file | # the call to `tail` to remove the 1st line is not necessary
sort -t, -k 1,1 |
awk -F ',+' -v OFS=, '$2==x{id=$1;a=$3;b=$4;c=$5;d=$6} id==$1 && $2==y{$3=a","$3; $4=b","$4; $5=c","$5; $6=d","$6; $2=""; $0=$0; $1=$1; print}' \
x=J1 y=S1
Just replace the value of the argument x and y with what you like.
Please note the value of x and y must follow the alphabet order, e.g., x=J1 y=S1 is OK, but x=S1 y=J1 doesn't work.
VERSION 2
The limitation mentioned in VERSION 1 that you have to specify the x and y in alphabet order is removed. Like, x=S1 y=J1 is OK now.
tail -n +2 file | # the call to `tail` to remove the 1st line is not necessary
sort -t, -k 1,1 |
awk -F ',+' -v OFS=, 'id!=$1 && ($2==x||$2==y){z=$2==x?y:x; id=$1; a=$3;b=$4;c=$5;d=$6} id==$1 && $2==z{$3=a","$3;$4=b","$4;$5=c","$5;$6=d","$6; $2=""; $0=$0; $1=$1; print}' \
x=S1 y=J1
However, the data of J1 is still put before the data of S1, which means the column a1 in the resulting output is always the column a of J1 in the input file, and a2 in the resulting output is always the column a of S1 in the input file.
VERSION 3
The limitation mentioned in the VERSION 2 is removed. Now with x=S1 y=J1, the output column a1 would be the input column a of S1, and the a2 would be the a of J1.
tail -n +2 file | # the call to `tail` to remove the 1st line is not necessary
sort -t, -k 1,1 |
awk -F ',+' -v OFS=, 'id!=$1 && ($2==x||$2==y){z=$2==x?y:x; id=$1; a=$3;b=$4;c=$5;d=$6} id==$1 && $2==z{if (z==y) {$3=a","$3;$4=b","$4;$5=c","$5;$6=d","$6} else {$3=$3","a;$4=$4","b;$5=$5","c;$6=$6","d} $2=""; $0=$0; $1=$1; print}' \
x=S1 y=J1

splitting file into smaller files using by number of fields

I'm having a hard time breaking a large (50GB) csv file into smaller part. Each line has a few thousand fields. Some of the fields are strings in double quotes, others are integers, decimals and boolean.
I want to parse the file line by line and split by the number of fields in each row. The strings contain possibly several commas (such as ), as well as a number of empty fields.
,,1,30,50,"Sold by father,son and daughter for $4,000" , ,,,, 12,,,20.9,0,
I tried using
perl -pe' s{("[^"]+")}{($x=$1)=~tr/,/|/;$x}ge ' file >> file2
to change the commas inside the quotes to | but that didn't work. I plan to use
awk -F"|" conditional statement appending to new k_fld_files file2
Is there an easier way to do this please? I'm looking at python, but I probably need a utility that will stream process the file, line by line.

Using Python - if you just want to parse CSV including embedded delimiters, and stream out with a new delimiter, then something such as:
import csv
import sys
with open('filename.csv') as fin:
csvout = csv.writer(sys.stdout, delimiter='|')
for row in csv.reader(fin):
csvout.writerow(row)
Otherwise, it's not much more difficult to make this do all kinds of stuff.
Example of outputting to files per column (untested):
cols_to_output = {}
for row in csv.reader(fin):
for colno, col in enumerate(row):
output_to = cols_to_output.setdefault(colno, open('column_output.{}'.format(colno), 'wb')
csv.writer(output_to).writerow(row)
for fileno in cols_to_output.itervalues():
fileno.close()

Here's an awk alternative.
Assuming the quoted strings are well formatted, i.e. always have starting and terminating quotes, and no quotes within other quotes, you could do the replacement you suggested by doing a gsub on every other field replacing , with |.
With pipes
Below is an example of how this might go when grabbing columns 3 through 6, 11 and 14-15 with coreutils cut:
awk -F'"' -v OFS='' '
NF > 1 {
for(i=2; i<=NF; i+=2) {
gsub(",", "|", $i);
$i = FS $i FS; # reinsert the quotes
}
print
}'\
| cut -d , -f 3-6,11,14-15 \
| awk -F'"' -v OFS='' -e '
NF > 1 {
for(i=2; i<=NF; i+=2) {
gsub("\\|", ",", $i)
$i = FS $i FS; # reinsert the quotes
}
print
}'
Note that there is an additional post-processing step that reverts the | to ,.
Entirely in awk
Alternatively, you could do the whole thing in awk with some loss of generality with regards to range specification. Here we only grab columns 3 to 6:
extract.awk
BEGIN {
OFS = ""
start = 3
end = 6
}
{
for(i=2; i<=NF; i+=2) {
gsub(",", "|", $i)
$i = FS $i FS
}
split($0, record, ",")
for(i=start; i<=end-1; i++) {
gsub("\\|", ",", record[i])
printf("%s,", record[i])
}
gsub("\\|", ",", record[end])
printf("%s\n", record[end])
}

Summing up two columns the Unix way

# To fix the symptom
How can you sum up the following columns effectively?
Column 1
1
3
3
...
Column 2
2323
343
232
...
This should give me
Expected result
2324
346
235
...
I have the columns in two files.
# Initial situation
I use sometimes too many curly brackets such that I have used one more this { than this } in my files.
I am trying to find where I have used the one unnecessary curly bracket.
I have used the following steps in getting the data
Find commands
find . * -exec grep '{' {} + > /tmp/1
find . * -exec grep '}' {} + > /tmp/2
AWK commands
awk -F: '{ print $2 }' /tmp/1 > /tmp/11
awk -F: '{ print $2 }' /tmp/2 > /tmp/22
The column are in the files /tmp/11 and /tmp/22.
I repeat a lot of similar commands in my procedure.
This suggests me that this is not the right way.
Please, suggests me any way such as Python, Perl or any Unix tool which can decrease the number of steps.

If c1 and c2 are youre files, you can do this:
$ paste c1 c2 | awk '{print $1 + $2}'
Or (without AWK):
$ paste c1 c2 | while read i j; do echo $(($i+$j)); done

Using python:
totals = [ int(i)+int(j) for i, j in zip ( open(fname1), open(fname2) ) ]

You can avoid the intermediate steps by just using a command that do the counts and the comparison at the same time:
find . -type f -exec perl -nle 'END { print $ARGV if $h{"{"} != $h{"}"} } $h{$_}++ for /([}{])/g' {}\;
This calls the Perl program once per file, the Perl program counts the number of each type curly brace and prints the name of the file if they counts don't match.
You must be careful with the /([}{]])/ section, find will think it needs to do the replacement on {} if you say /([{}]])/.
WARNING: this code will have false positives and negatives if you are trying to run it against source code. Consider the following cases:
balanced, but curlies in strings:
if ($s eq '{') {
print "I saw a {\n"
}
unbalanced, but curlies in strings:
while (1) {
print "}";
You can expand the Perl command by using B::Deparse:
perl -MO=Deparse -nle 'END { print $ARGV if $h{"{"} != $h{"}"} } $h{$_}++ for /([}{])/g'
Which results in:
BEGIN { $/ = "\n"; $\ = "\n"; }
LINE: while (defined($_ = <ARGV>)) {
chomp $_;
sub END {
print $ARGV if $h{'{'} != $h{'}'};
}
;
++$h{$_} foreach (/([}{])/g);
}
We can now look at each piece of the program:
BEGIN { $/ = "\n"; $\ = "\n"; }
This is caused by the -l option. It sets both the input and output record separators to "\n". This means anything read in will be broken into records based "\n" and any print statement will have "\n" appended to it.
LINE: while (defined($_ = <ARGV>)) {
}
This is created by the -n option. It loops over every file passed in via the commandline (or STDIN if no files are passed) reading each line of those files. This also happens to set $ARGV to the last file read by <ARGV>.
chomp $_;
This removes whatever is in the $/ variable from the line that was just read ($_), it does nothing useful here. It was caused by the -l option.
sub END {
print $ARGV if $h{'{'} != $h{'}'};
}
This is an END block, this code will run at the end of the program. It prints $ARGV (the name of the file last read from, see above) if the values stored in %h associated with the keys '{' and '}' are equal.
++$h{$_} foreach (/([}{])/g);
This needs to be broken down further:
/
( #begin capture
[}{] #match any of the '}' or '{' characters
) #end capture
/gx
Is a regex that returns a list of '{' and '}' characters that are in the string being matched. Since no string was specified the $_ variable (which holds the line last read from the file, see above) will be matched against. That list is fed into the foreach statement which then runs the statement it is in front of for each item (hence the name) in the list. It also sets $_ (as you can see $_ is a popular variable in Perl) to be the item from the list.
++h{$_}
This line increments the value in $h that is associated with $_ (which will be either '{' or '}', see above) by one.

In Python (or Perl, Awk, &c) you can reasonably do it in a single stand-alone "pass" -- I'm not sure what you mean by "too many curly brackets", but you can surely count curly use per file. For example (unless you have to worry about multi-GB files), the 10 files using most curly braces:
import heapq
import os
import re
curliest = dict()
for path, dirs, files in os.walk('.'):
for afile in files:
fn = os.path.join(path, afile)
with open(fn) as f:
data = f.read()
braces = data.count('{') + data.count('}')
curliest[fn] = bracs
top10 = heapq.nlargest(10, curlies, curliest.get)
top10.sort(key=curliest.get)
for fn in top10:
print '%6d %s' % (curliest[fn], fn)

Reply to Lutz'n answer
My problem was finally solved by this commnad
paste -d: /tmp/1 /tmp/2 | awk -F: '{ print $1 "\t" $2 - $4 }'

your problem can be solved with just 1 awk command...
awk '{getline i<"file1";print i+$0}' file2