In [34]:
import os
os.chdir('/home/mckc/clean')
In [35]:
files = os.listdir(os.getcwd())
In [42]:
for i in files:
os.rename(i, i[:a-4]+'_1'+i[a-4:])
In [41]:
for i in files:
a = len(i)
print i[:a-4]+'_1'+i[a-4:]
In [ ]: