How to read and write multiple files?

Question

I want to write a program for this: In a folder I have n number of files; first read one file and perform some operation then store result in a separate file. Then

Answer 1

from pylab import * 
import csv 
import os 
import glob 
import re 
x=[] 
y=[]

f=open("one.txt",'w')

for infile in glob.glob(('*.csv')):
    #   print "" +infile
    csv23=csv2rec(""+infile,'rb',delimiter=',')
    for line in csv23:      
        x.append(line[1])
        #  print len(x)
    for i in range(3000,8000):
        y.append(x[i])
    print ""+infile,"\t",mean(y)
    print >>f,""+infile,"\t\t",mean(y)
    del y[:len(y)]
    del x[:len(x)]