python code that separate 150000 records into 15 small files

fa = open ('b150000.txt','r')

n = 1

fb = open ('b-1.txt','w')

i = 0

for line in fa:

# 1 to 10000 for first 10001 to 20000 for second

if((i/10000 +1)!=n):

n=i/10000 + 1

fb.close()

fb = open('b-'+str(n)+'.txt','w')

fb.write(line)

i = i + 1

fa.close()

fb.close()