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Python Program to Print Lines Containing Given String in File

  • Last Updated : 31 Aug, 2021
Geek Week

In this article, we are going to see how to fetch and display lines containing a given string from a given text file. Assume that you have a text file named geeks.txt saved on the location where you are going to create your python file.

Here is the content of the geeks.txt file:

Approach:

  • Load the text file into the python program to find the given string in the file.
  • Ask the user to enter the string that you want to search in the file.
  • Read the text file line by line using readlines() function and search for the string.
  • After finding the string, print that entire line and continue the search.
  • If the string is not found in the entire file, display the proper verdict.

Below is the implementation:



Python3




# Python Program to Print Lines
# Containing Given String in File
  
# input file name with extension
file_name = input("Enter The File's Name: ")
  
# using try catch except to
# handle file not found error.
  
# entering try block
try:
  
    # opening and reading the file 
    file_read = open(file_name, "r")
  
    # asking the user to enter the string to be 
    # searched
    text = input("Enter the String: ")
  
    # reading file content line by line.
    lines = file_read.readlines()
  
    new_list = []
    idx = 0
  
    # looping through each line in the file
    for line in lines:
          
        # if line have the input string, get the index 
        # of that line and put the
        # line into newly created list 
        if text in line:
            new_list.insert(idx, line)
            idx += 1
  
    # closing file after reading
    file_read.close()
  
    # if length of new list is 0 that means 
    # the input string doesn't
    # found in the text file
    if len(new_list)==0:
        print("\n\"" +text+ "\" is not found in \"" +file_name+ "\"!")
    else:
  
        # displaying the lines 
        # containing given string
        lineLen = len(new_list)
        print("\n**** Lines containing \"" +text+ "\" ****\n")
        for i in range(lineLen):
            print(end=new_list[i])
        print()
  
# entering except block
# if input file doesn't exist 
except :
  print("\nThe file doesn't exist!")

Output:

Lines containing string

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