The get_opcodes() method of SequenceMatcher class

Overview:

Using the operations replace, delete, insert and equal a sequence s1 can be transformed into another sequence s2.
The get_opcodes() returns the required number of operations to transform one sequence into another as a list of tuples. Each tuple contains one opcode.

Each tuple consists of the following information:
An opcode describing the operation to be performed on the substring of sequence – s1. An opcode assumes one of the following values ‘replace’, ‘delete’, ‘insert’ and ‘equal’.
The start index of the substring of sequence s1
The end index of the substring of sequence s1
The start index of the substring of sequence s2
The end index of the substring of sequence s2

In Python, a substring of s is denoted as string[start:end] where start index is included in the substring and the end index is not included in the substring.

Example:

# Example Python program that gets the opcodes
# to make sequence1 into sequence2 using the
# get_opcodes() method of the SequenceMatcher object
import difflib

# The sequences
string1 = "Humpty Dumpty sat on a wall"
string2 = "Humpty Dumpty had a great fall"

# Create a SequenceMatcher object
seqMatcher = difflib.SequenceMatcher()

# Set the sequences to the SequenceMatcher
seqMatcher.set_seq1(string1)
seqMatcher.set_seq2(string2)

# Get the opcodes
opCodes = seqMatcher.get_opcodes()

print("The opcodes to turn string1 into string2:")
print(opCodes)

Output:

The opcodes to turn string1 into string2:
[('equal', 0, 14, 0, 14), ('replace', 14, 15, 14, 23), ('equal', 15, 18, 23, 26), ('replace', 18, 24, 26, 27), ('equal', 24, 27, 27, 30)]