Question

for line in open('file.txt'):
    print(re.sub('windows', 'linux', line))

or

print(re.sub('windows', 'linux', open('file.txt').read()))

Which one is better? Is there any differences?
BTW. Is is a good idea to manipulate a huge string with a regex?

Answer 1

As Polynomial said, the second one reads the whole file into RAM, which may or may not be better.

But there is another solution:

with open('file.txt') as file:
    for line in file:
        print(re.sub('windows', 'linux', line))

This ensures that the file will be closed immediately after not needing it any longer.

Similiarly,

with open('file.txt') as file:
    print(re.sub('windows', 'linux', file.read()))

can be used as well.