file=open('directory/file.htm','r')
for j in file:
	lines=file.readline()
for i in range(len(lines)):
	lines[i].replace('слово_1','слово_2')
for y in range(len(lines)):
	print lines

lines=file.read()
print lines

print open(r'directory/file.htm').read().replace('слово_1','слово_2')

for line in f:
    sys.stdout.write(line.replace('abc', 'def'))