faster code for my code

[kucingkembar]

hi, sorry for my bad English,
I have code to remove line(s) that do not start with '[' and end with ']':

    with open('input.raw') as f:
        lines = ""
        for line in f:
            lina = line.strip()
            #print(line)
            if lina.startswith("["):
                if lina.endswith("]"):
                    lines = lines + lina + "\n"
    writing = open('output.raw', 'w')
    writing.write(lines)
    writing.close()

but somehow my file is over 200Mb, and it take hour(s) to get it done,
som how make my code faster?

[Gribouillis]

The slow part is the accumulative string concatenation at line 8 (the + operator). Try this code

def good_lines(file):
    for line in file:
        line = line.strip()
        if line[:1] == '[' and line[-1] == ']':
            yield line + '\n'

with open('input.raw') as ifh, open('output.raw', 'w') as ofh:
    ofh.writelines(good_lines(ifh))

[kucingkembar]

The slow part is the accumulative string concatenation at line 8 (the + operator). Try this code

def good_lines(file):
    for line in file:
        line = line.strip()
        if line[:1] == '[' and line[-1] == ']':
            yield line + '\n'

with open('input.raw') as ifh, open('output.raw', 'w') as ofh:
    ofh.writelines(good_lines(ifh))

can you belive it, it make hours to under a minute,
thank you, I will give you reputation point

[ndc85430]

Is there a reason you're writing this yourself and not using existing tools like, say, grep?

[kucingkembar]

Is there a reason you're writing this yourself and not using existing tools like, say, grep?

what is grep? any link of it?

[rob101]

what is grep? any link of it?

https://www.man7.org/linux/man-pages/man1/grep.1.html

[kucingkembar]

what is grep? any link of it?

https://www.man7.org/linux/man-pages/man1/grep.1.html

something error, I tried this:

C:\Users\GIGABYTE>pip install grep
Collecting grep
  Downloading grep-0.3.2.tar.gz (3.2 kB)
  Preparing metadata (setup.py) ... done
Using legacy 'setup.py install' for grep, since package 'wheel' is not installed.
Installing collected packages: grep
  Running setup.py install for grep ... done
Successfully installed grep-0.3.2

C:\Users\GIGABYTE>grep
'grep' is not recognized as an internal or external command,
operable program or batch file.

I will study this

[rob101]

something error, I tried this:

I think that you're confused. grep as I know it, is a command-line utility for searching plain-text data sets for lines that match a regular expression and is a part of Unix type computer operating systems (I can't speak for MS Windows OS, as I don't use it), but so far as I know, there is no Python library of the same name: I stand to be corrected on that, if I'm wrong.

For a regular expression pattern match, I'd use regex:

import re
re.search(<regex>, <string>)

[kucingkembar]

something error, I tried this:

I think that you're confused. grep as I know it, is a command-line utility for searching plain-text data sets for lines that match a regular expression and is a part of Unix type computer operating systems (I can't speak for MS Windows OS, as I don't use it), but so far as I know, there is no Python library of the same name: I stand to be corrected on that, if I'm wrong.

For a regular expression pattern match, I'd use regex:

import re
re.search(<regex>, <string>)

that linux thing, that why I not use it

anyway is there any regex tutorial with lots of example?

[deanhystad]

The rough Windows equivalent of grep is findstr. (CMD shell) or Select-String (PowerShell)

https://docs.microsoft.com/en-us/windows...ds/findstr
https://docs.microsoft.com/en-us/powersh...rshell-7.2