import os
for i in [1..2]:
s = open("a.tex").read()
lines = s.split("\n")
lines[lines.index("\\newcommand{\\banana}{cat}")] = "\\newcommand{\\banana}{%d}" % i
if not os.path.exists("dir%d" % i):
os.makedirs("dir%d" % i)
f = open("dir%d/a.tex" % i,'w')
f.write("\n".join(lines))
f.close()