How to grep lines between two patterns in a big file with python

Question

I have a very big file, like this:

[PATTERN1]
line1
line2
line3 
...
...
[END PATTERN]
[PATTERN2]
line1 
line2
...
...
[END PATTERN]

I need to extract

Answer 1

I think this does the same thing your code does:

FILE=open('myfile').readlines()

newfile=[]

pattern = None
for line in FILE:
    if line[0] == "[" and line[-1] == "]":
        pattern = line[1:-1]
        if pattern == "END PATTERN":
            pattern = None
        continue
    elif pattern is not None and pattern in name_list:
        newfile.append(line)

This way you go through all the lines only once, and fill your list as you go.