Read Multiple Block Of File Between Start And Stop Flags

I am trying to read sections of a file into numpy arrays that have similar start and stop flags for the different sections of the file. At the moment I have found a method that wo

Solution 1:

You can use itertools.takewhile each time you reach the start flag to take until the stop:

from itertools import takewhile
withopen("myFile.txt") as f:
        array = []
        for line in f:
            if line.startswith('start flag'):               
                data = takewhile(lambda x: not x.startswith("stop flag"),f)
                # use data and repeat

Or just use an inner loop:

withopen("myFile.txt") as f:
    array = []
    for line in f:
        if line.startswith('start flag'):
            # beginning of section use first linfor line in f:
                # check for end of section breaking if we find the stop loneif line.startswith("stop flag"):
                    break# else process lines from section

A file object returns its own iterator so the pointer will keep moving as you iterate over f, when you reach the start flag, start processing a section until you hit the stop. There is no reason to re-open the file at all, just use the sections as you iterate once over the lines of the file. If the start and stop flag lines are considered part of the section make sure to also use those too.

Solution 2:

You have indentation problem, your code should look like this:

withopen("myFile.txt") as f:
    array = []
    parsing = Falsefor line in f:
        if line.startswith('stop flag'):
        parsing = Falseif parsing:
        #do things to the dataif line.startswith('start flag'):
        parsing = True

Solution 3:

The solution similar to yours would be:

result = []
parse = Falsewithopen("myFile.txt") as f:
    for line in f:
        if line.startswith('stop flag'):
            parse = Falseelif line.startswith('start flag'):
            parse = Trueelif parse:
            result.append(line)
        else:  # not needed, but I like to always add else clausecontinueprint result

But you might also use inner loop or itertools.takewhile as other answers suggest. Especially using takewhile should be significantly faster for really big files.

Solution 4:

Let's say this is your file to read:

**starting** blabla blabla **starting** bleble bleble **starting** bumbum bumbum

This is code of the program:

file = open("testfile.txt", "r")
data = file.read()
file.close
data = data.split("**starting**")
print(data)

And this is output:

['', '\nblabla\nblabla\n', '\nbleble\nbleble\n', '\nbumbum\nbumbum']

Later you can del empty element, or do other operation in your data. split function is buildin for string objects and can get more complicated strings as arguments.