Technology DB

First obtain a cursor

import MySQLdb
conn = MySQLdb.connect (host = “localhost”, user = “root”, passwd = “”, db = “dbname”)
cursor = conn.cursor()

Now execute mysql sql query

sql = “select COLA, COLB from T1 where COLC=%”
colc_value = “something”
cursor.execute(sql, [colc_value])

Now iterate over results

while(1):
data = cursor.fetchone()
if data == None: break
desc = cursor.description
dict = {}
for (name, value) in zip(desc, data):
dict[str(name[0])] = value
print dict

import socket
host = socket.gethostname()
print host

Sometimes we want to iterate over a dictionary in sorted order of value. Here is the code:

d = {”a”:1, “b”:5, “c”:2, “be”:30}
for k in sorted(d.keys(), lambda x,y:d[x]-d[y]):
print “%s=%s” % (k, d[k])

# output is:
a=1
c=2
b=5
be=30

Here are some cool python one liners.

• Parse apache log using python: print 5th field
  python -c “import csv,sys;f=csv.reader(sys.stdin, delimiter=’ ‘); print ‘\n’.join([r[5] for r in f])
• Generate frequency histogram from a text files of terms
  cat file.txt | sort | uniq -c | sort -rn
• print 2nd column of a tab separated file
  awk -F”\t” ‘{print $2}’
• perl search replace from files
  perl -i -p -e ’s/old/new/g’