Why ps output gets truncated when called from script?

Issue

• I am calling ps from a script and its output gets truncated on width
• How to set windowsize in pexpect module?

[root@]# cat file
#!/usr/bin/python

import pexpect

p=pexpect.spawn('ps -eaf')
p.setwinsize(44,250)
p.expect(pexpect.EOF)
print p.before
p.close()

expected output:
<<>>
[root@]# ps -eaf | grep python
root      2388     1  0 Feb24 ?        00:00:10 /usr/bin/python /usr/sbin/osad --pid-file /var/run/osad.pid
root     15738 13272  0 16:20 pts/4    00:00:00 grep python
root     63794     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/SSL_server.py SSL
root     63803     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/DomainAuthentication.py SSL
root     63812     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/LocalAuthentication.py SSL
root     63821     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/AcL.py SSL
<<>>

after execution script gives following truncated output

[root@]# ./file | grep python
root      2388     1  0 Feb24 ?        00:00:10 /usr/bin/python /usr/sbin/osad -
root     15253 13272  0 15:47 pts/4    00:00:00 /usr/bin/python ./file
root     15254 13272  0 15:47 pts/4    00:00:00 grep python
root     63794     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/Pyt
root     63803     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/Pyt
root     63812     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/Pyt
root     63821     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/Pyt

• After going through pexpect.py script , I can see it run the setwinsize fuction with default value of 24,80

[root]# cat -n /usr/lib/python2.6/site-packages/pexpect.py | grep setwinsize
   535                  self.child_fd = sys.stdout.fileno() # used by setwinsize()
   536                  self.setwinsize(24, 80)
   538                  # Some platforms do not like setwinsize (Cygwin).
  1427      def setwinsize(self, r, c):
  1479                  p.setwinsize(a[0],a[1])

• I created a local copy of pexpect.py script & changed the value from 24,80 to 24,200 & executed the script

output of the script ( as expected )

[root@]# ./file | grep python
root      2388     1  0 Feb24 ?        00:00:10 /usr/bin/python /usr/sbin/osad --pid-file /var/run/osad.pid
root     15285 13272  3 15:49 pts/4    00:00:00 /usr/bin/python ./file
root     15286 13272  0 15:49 pts/4    00:00:00 grep python
root     63794     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/SSL_server.py SSL
root     63803     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/DomainAuthentication.py SSL
root     63812     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/LocalAuthentication.py SSL
root     63821     1  0 Mar05 ?        00:00:00 /usr/bin/python /root/python/PythonGui/AcL.py SSL