Reading file between headers in python

Question

I have a large text file that has values ​​separated by a header starting with "#". If the condition matches the condition in the header, I would like to read the file until the next header "#" and the rest of the SKIP file.

To verify that I am trying to read the following text file called test234.txt:

# abcdefgh
1fnrnf
mrkfr
nfoiernfr
nerfnr
# something
njndjen kj
ejkndjke
#vcrvr

The code I wrote is:

file_t = open('test234.txt')
cond = True
while cond:
    for line_ in file_t:
        print(line_)
        if file_t.read(1) == "#":
            cond = False
file_t.close()

But the output that I get is:

# abcdefgh

fnrnf

rkfr

foiernfr

erfnr

something

jndjen kj

jkndjke

vcrvr

Instead, I would like to get output between two headers separated by "#", which:

1fnrnf
mrkfr
nfoiernfr
nerfnr      

How can i do this? Thank!

EDIT: python , , , , , , "#", .

Answer 1

itertools.groupby :

from io import StringIO
from itertools import groupby

text = '''# abcdefgh
1fnrnf
mrkfr
nfoiernfr
nerfnr
# something
njndjen kj
ejkndjke
#vcrvr'''


with StringIO(text) as file:
    lines = (line.strip() for line in file)  # removing trailing '\n'
    for key, group in groupby(lines, key=lambda x: x[0]=='#'):

        if key is True:
            # found a line that starts with '#'
            print('found header: {}'.format(next(group)))

        if key is False:
            # group now contanins all lines that do not start with '#'
            print('\n'.join(group))

, . .

with StringIO(text) as file: ; with open('test234.txt', 'r') as file:...

:

found header: # abcdefgh
1fnrnf
mrkfr
nfoiernfr
nerfnr
found header: # something
njndjen kj
ejkndjke
found header: #vcrvr

---

UPDATE, . :

from io import StringIO
from collections import deque
from itertools import takewhile

from_line = '# abcdefgh'
to_line = '# something'

with StringIO(text) as file:
    lines = (line.strip() for line in file)  # removing trailing '\n'

    # fast-forward up to from_line
    deque(takewhile(lambda x: x != from_line, lines), maxlen=0)

    for line in takewhile(lambda x: x != to_line, lines):
        print(line)

itertools.takewhile, , ( ).

deque - consume pattern, itertools. , .

Answer 2

. .

import re #regex library

with open('test234.txt') as f:  #file stream
    lines = f.readlines()       #reads all lines

p = re.compile('^#.*')          #regex pattern creation

for l in lines:
    if p.match(l) == None:      #looks for non-matching lines
        print(l[:-2])