How do I extract a particular section from textfile in python3 - python-3.x

Question

This is my python file
path = '/my/file/list.txt'
with open(path,'rt') as file:
print("step 1")
collected_lines = []
started = False
for line in file:
for n in range(1, 10):
if line.startswith('PLAY NO.{}'.format(n)):
started = True
print("started at line {}".format(line[0]))
continue
if started:
collected_lines.append(line)
if started and line == 'PLAY NO.{}'.format(n+1):
print("end at line {}".format(line[0]))
break
print(collected_lines.append(line))
This is my code..
OUTPUT:
None
None
None
None
None
None
Now I want the lines starting from play No2 to play No3.... But I am getting None.. Please any suggestions... I am using Python 3.5
Sorry this is the first time asking question on this site..
My file looks like this..
textfile.txt
Hello and Welcome This is the list of plays being performed here
PLAY NO. 1
1. adknjkd
2. skdi
3. ljdij
PLAY NO. 2
1. hsnfhkjdnckj
2. sjndkjhnd and so on

Answer 1

path = 'list.txt'
collected_lines = []
with open(path,'rt') as file:
print("step 1")
started = False
lineNo = 0
for line in file:
lineNo += 1
for n in range(1, 10):
# print('PLAY NO. {}'.format(n))
if started and line.lstrip().startswith('PLAY NO. {}'.format(n)):
print("### end at line {}".format(lineNo))
started = False
break
if line.lstrip().startswith('PLAY NO. {}'.format(n)):
started = True
print("### started at line {}".format(lineNo))
break
if started:
collected_lines.append(line)
print("collected_lines: \n\n", *[ item for item in collected_lines ])
gives:
step 1
### started at line 2
### end at line 7
collected_lines:
PLAY NO. 1
1. adknjkd
2. skdi
3. ljdij
NOTES about fixed issues:
used .lstrip() in order to make .startswith() working as expected
added a space between NO. and {} in startswith('PLAY NO. {}'.format(n) so that the if condition can find the line
rearranged the order of ifs in order to avoid that the end line is considered found at the start line
added started = False to the loop to stop collecting the lines.
The problem with the leading spaces was already enough to prevent the code from finding the line. Fixing this alone wouldn't fix the problem because of the missing space in the format string, so both issues had to be fixed to make the code work as expected. And so on ... see NOTES above.

Answer 2

If you want a dict with as labels the play number and as items a list with the lines about the play you can use a defaultdict
Defining the text
text = """Hello and Welcome This is the list of plays being performed here
PLAY NO. 1
1. adknjkd
2. skdi
3. ljdij
PLAY NO. 2
1. hsnfhkjdnckj
2. sjndkjhnd and so on"""
Defining the regular expression
regex = re.compile('^\s*PLAY NO. (\d+)$')
Parsing the lines
label = None # no play to start with
recorded_lines = defaultdict(list)
for line_no, line in enumerate(StringIO(text)):
# In the real code replace the 'StringIO(text)' with 'file'
try:
play_no = int(regex.findall(line)[0])
# If this regex does not match, it will throw an IndexError
# The code underneath is only executed when a new play starts
if label: # if there is no play underway, there can be no ending
print('PLAY NO. %i ended at line number %i' % (label, line_no-1))
label = play_no
print('PLAY NO. %i started at line number %i' % (play_no, line_no))
except IndexError:
# no new play started
if label and line.strip():
recorded_lines[play_no].append(line.strip())
print(line_no, line)
print(recorded_lines)
yields
defaultdict(list,
{1: [(2, '1. adknjkd'), (3, '2. skdi'), (4, '3. ljdij')],
2: [(7, '1. hsnfhkjdnckj'), (8, '2. sjndkjhnd and so on')]})
and this output on the stout:
0 Hello and Welcome This is the list of plays being performed here
PLAY NO. 1 started at line number 1
1 PLAY NO. 1
2 1. adknjkd
3 2. skdi
4 3. ljdij
5
PLAY NO. 1 ended at line number 5
PLAY NO. 2 started at line number 6
6 PLAY NO. 2
7 1. hsnfhkjdnckj
8 2. sjndkjhnd and so on