Python Program to Compare Two Text Files

Let us look at how to compare two text files in Python in this tutorial. We will use a variety of approaches to try to solve this problem.

Let us consider the below two text files as an example:

demotextfile_1.txt:

hello this is Python-programs 
good morning all
Then give a start to it 
welcome to the greatest python coding platform

demotextfile_2.txt:

hello this is Python-programs 
Are you good at coding? 
Then give a start to it 
good morning all

Program to Compare Two Text Files in Python

Below are the ways to compare two text files in Python:

Using filecmp.cmp() Method
Using line by line Comparision

Method #1: Using filecmp.cmp() Method

Python has a filecmp module that allows you to compare files. The filecmp.cmp() function returns a three-list of matched, errors, and mismatched files. filecmp.cmp() has two modes of operation.

shallow mode: In this mode, only file metadata such as size, modified date, and so on are compared.
deep mode: The content of the files is compared in this mode.

Approach:

Import filecmp module using the import keyword
Import os module using the import keyword
Give the first textfile as static input and store it in a variable.
Give the second textfile as static input and store it in another variable.
Pass the above given first and second text files as arguments to the cmp() function of the filecmp module to compare metadata in shallow mode
Returns True if both the textfiles are the same else False
Pass the above given first and second text files as arguments to the cmp() function of the filecmp module to comapre content in deep mode( shallow=False)
Returns True if both the textfiles are the same else False.
The Exit of the Program.

Below is the implementation:

# Import filecmp module using the import keyword 
import filecmp
# Import os module using the import keyword 
import os
# Give the first textfile as static input and store it in a variable.
Textfile_1 = "demotextfile_1.txt"
# Give the second textfile as static input and store it in another variable.
Textfile_2 = "demotextfile_2.txt"

# Pass the above given first and second text files as arguments to the cmp() function 
# of the filecmp module to compare metadata in shallow mode
# Returns True if both the textfiles are same else False
rslt = filecmp.cmp(Textfile_1, Textfile_2)
print(rslt)

# Pass the above given first and second text files as arguments to the cmp() function 
# of the filecmp module to comapre content in deep mode( shallow=False)
# Returns True if both the textfiles are same else False
rslt = filecmp.cmp(Textfile_1, Textfile_2, shallow=False)
print(rslt)

Output:

False
False

Method #2: Using line by line Comparision

Approach:

Open the first text file in read-only mode using the open() function by passing filename/path, mode as arguments to it and store it in a variable.
Open the second text file in read-only mode using the open() function by passing filename/path, mode as arguments to it and store it in another variable.
Take a variable and initialize its value with 0 which represents the line number.
Loop in each line of the given first text file using the for loop.
Increment the above initialized variable value by 1 which holds the line number.
Loop in each line of the given second text file using the other nested for loop.
Check if each line of the first text file is equal/similar to the corresponding line of the second text file using the if conditional statement.
If it is true, then print the respective line number.
Print Both the lines of given two text file are the same.
Else print the respective line number and corresponding lines of both the text files.
Close the given first text file using the close() function.
Close the given second text file using the close() function.
The Exit of the Program.

Below is the implementation:

# Open the first text file in read-only mode using the open() function
# by passing filename/path, mode as arguments to it and store it in a variable.
Textfile_1 = open("demotextfile_1.txt", "r")
# Open the second text file in read-only mode using the open() function
# by passing filename/path, mode as arguments to it and store it in another variable.
Textfile_2 = open("demotextfile_2.txt", "r")
# Take a variable and initialize its value with 0 which represents the line number
i = 0
# Loop in each line of the given first text file using the for loop
for f1_line in Textfile_1:
    # Increment the above initialized variable value by 1 which holds the line number
    i += 1
    # Loop in each line of the given second text file using the other nested for loop
    for f2_line in Textfile_2:
      # Check if each line of the first text file is equal/similar to the corresponding line 
      # of the second text file using the if conditional statement
      if f1_line == f2_line:
          # If it is true, then print the respective line number 
          print("line_",i,": ")
          # Print Both the lines of given two text file are the same
          print("Both the lines of given two text file are the same")
          print()
      else:
          # Else print the respective line number and corresponding lines of 
          # both the text files
          print("line_",i,": ")
          print("Textfile_1: ", f1_line)
          print("Textfile_2: ", f2_line)
      break

# Close the given first text file using the close() function
Textfile_1.close()
# Close the given second text file using the close() function
Textfile_2.close()

Output:

line_ 1 : 
Both the lines of given two text file are the same

line_ 2 : 
Textfile_1: good morning all

Textfile_2: Are you good at coding?

line_ 3 : 
Both the lines of given two text file are the same

line_ 4 : 
Textfile_1: welcome to the greatest python coding platform

Textfile_2: good morning all