How to read particular text lines with python?-CodePudding

I want to read particular lines from the text file. E.g. all the contents between "This contents information"

I have created a script to perform the task, but it's not a good method. Are there any better way to do it?

readText=open("test.txt","r")

wanted_lines = [4,5,6,7]
count = 1
with open('test.txt', 'r') as infile:
     for line in infile:
          line = line.strip()
          if count in wanted_lines:
               print(line)
          else:
               pass
          count  = 1

CodePudding user response：

You can compare each line to the sentinel, start outputting once it matches, and stop outputting once it matches again:

with open('test.txt') as infile:
    for output in False, True:
        for line in map(str.rstrip, infile):
            if line == 'This contents information':
                break
            if output:
                print(line)

Demo: https://replit.com/@blhsing/TroubledMysteriousMonitors

CodePudding user response：

You could consider reading the entire text file into a string, and then using a regular expression to extract the contents you want:

with open('test.txt', 'r') as file:
    data = file.read()

contents = re.search(r'^This contents information\n(.*?)\nThis contents information\b', inp, flags=re.M|re.S).group(1)
print(contents)

This prints:

City:LK
Country:LL
Postcode:123

CodePudding user response：

You can use split, with "This contents information" as the delimiter.
In the example above, the file will be split into 3 sections, of which we only need to grab the second one (index=1). You can then use .strip() to remove unwanted space.

Code:

with open('test.txt', 'r') as infile:
     text = infile.read()

required_info = text.split("This contents information")[1].strip()

print(required_info)

Output:

City:LK
Country: LL
Postcode:123

CodePudding user response：

Instead of prewriting the line numbers, just have a conditional statement that checks for the data you want.

readText=open("test.txt","r")

with open('test.txt', 'r') as infile:
     for line in infile:
          line = line.strip()
          if line == "text to look for":
              printline = True
          elif line == "text to end content":
              printline = False
          elif printline == True:
              print(line)

CodePudding user response：

I think the best method would be to use regex.

import re

text=""
with open('test.txt', 'r') as infile:
    text = infile.read()

# Don't forget to replace here with the word you want to search among what you want to find.

# This contents information(.*?)\nThis contents information

# this regex finds everything between these two words

# example: 'test 123asda test' -> test(.*?)test =>  ' 123asda '

regex = re.compile(r'This contents information(.*?)\nThis contents information', re.DOTALL)
matches = [m.groups()[0] for m in regex.finditer(text)]

for m in matches:
    print(f'{m.strip()}')

CodePudding user response：

import re
with open("file.txt","r") as f:
    data =f.readlines()
    string="".join(data)
    lst=re.split(r"^This contents information\n",string)
    for i in range(len(lst)):
        print(lst(i).strip(),end="\n")