Shantanu's Blog

Corporate Consultant

June 26, 2013

 

Transpose data using python

# cat test.csv
name,height,weight
abc, 12,4
xyz, 6,4

I need to return the column values as list. So the names should return as a list with values like "abc, xyz"

with open('test.csv') as f:
    reader = csv.DictReader(f, delimiter=',')
    rows = list(reader)

names = [i['name'] for i in rows]
heights = [float(i['height']) if i['height'] else 0.0 for i in rows]
weights = [float(i['weight']) if i['weight'] else 0.0 for i in rows]

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Managing MySQL data in python

>>> import MySQLdb as db
>>> con = db.connect(user="foo", passwd="secret")
>>> cur = con.cursor()
>>> cur.execute('CREATE DATABASE chom;')

cur.execute ("SELECT name, category FROM animal")
rows = cur.fetchall ()
for row in rows:
    print "%s, %s" % (row[0], row[1])
print "%d rows were returned" % cur.rowcount

cur.execute ("""
CREATE TABLE animal
(
name CHAR(40),
category CHAR(40)
)
""")

http://www.cs.columbia.edu/~hgs/teaching/ap/examples/scripts_python_dbapi.pdf

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June 04, 2013

 

Kill processes

There are times when I check the process ID from "ps aux" command output and kill it. But it may take time to kill processes one at a time.
Easier way to kill multiple processes is by executing the following two functions.

function psgrep ()
{
ps aux | grep "$1" | grep -v 'grep'
}

function psterm ()
{
[ ${#} -eq 0 ] && echo "usage: $FUNCNAME STRING" && return 0
local pid
pid=$(ps ax | grep "$1" | grep -v grep | awk '{ print $1 }')
echo -e "terminating '$1' / process(es):\n$pid"
kill -SIGTERM $pid
}

You can add them to the .bash_profile so that these functions are available all the time. You can check the processes using "psgrep" function while killing them easy with "psterm".

# psgrep http

# psterm httpd
terminating 'httpd' / process(es):
31186
31187

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apache control

You can start apache with different directory using directive parameter

# httpd -k start -c “DocumentRoot /var/www/html_debug/”
If you want to go back to original configuration using the default DocumentRoot (/var/www/html), restart the Apache.
# httpd -k stop
# apachectl start

httpd -k start -e debug

Possible values you can pass to option -e are:
info
notice
warn
error
crit
alert
debug
emerg

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Managing history

// add date when the command was executed
export HISTTIMEFORMAT=’%F %T ‘

// ignore commands in history
export HISTIGNORE=”pwd:ls:ls –ltr:”
export HISTCONTROL=ignoredups
export HISTCONTROL=ignorespace

// clear all the previous history.
history -c

// disable history
export HISTSIZE=0

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Using command prompt to alter user

Using the export command we can change the linux command prompt to make it more informative. It is also possible to display the output of shell script as command prompt. For e.g. in the following example, when the disk space is 85% full, it will display a prompt.

export PS1="[\@] [`ifconfig | grep Bcast | awk '{print $2}' | awk -F':' '{print $2}'`] \$(diskfull.sh) > "

The new prompt will look something like this...

root@ip-10-158-57-83 disk full >

And the shell script:

cat /bin/diskfull.sh
#!/bin/sh

# set alert level 80% as default if no user input found
ALERT=${1:-95}

df -HP | grep -vE '^Filesystem|tmpfs|cdrom' | awk '{ print $5 " " $1 }' | while read output;
do
usep=$(echo $output | awk '{ print $1}' | cut -d'%' -f1 )
partition=$(echo $output | awk '{ print $2 }' )
if [ $usep -ge $ALERT ]; then
echo "disk full"
exit
fi
done

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June 01, 2013

 

Welcome infobright

Infobright is mysql compatible data ware house software. The free community version does not allow to insert / update /delete records. The only way to import data is to use "load data" statement. Here is a simple shell script that will copy the data from mysql to infobright. The table needs to be created in infobright manually. It is not part of this script because mysql datatypes and indexes needs to be modified.

#!/bin/sh

ibdata='test'
ibtable='window_way'

mysqlshow | awk '{print $2}' | while read dbname
do

rm -f /tmp/load.txt
rm -rf /tmp/$ibdata

time mysql -uroot -pPassWdsql $dbname -e"select *, database() into outfile '/tmp/load.txt' from $ibtable"

time mysql-ib -uroot -pPassWdIB $ibdata -e"set @BH_REJECT_FILE_PATH = '/tmp/$ibdata'; set @BH_ABORT_ON_COUNT = 1000; load data infile '/tmp/load.txt' into table $ibtable fields terminated by '\t' "

done

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