Python Program to Replace a Particular Word by Another Word from a given String

March 23, 2022

Replace a Particular Word with Another Word in Python

Here on this page, we will learn to create a Python Program to Replace a Particular Word with Another Word.

Example :

  • Input : s = “Let’s Learn Python from Internet”, s1 = “Internet”, s2 = “PrepInsta”

  • Output : “Let’s Learn Python from PrepInsta”

Replace a Particular Word with Another Word in Python

Method Discussed :

  • Method 1: Brute force approach
  • Method 2: In-place Replacing

Method 1

Algorithm

  • Initialize variable ans which will store empty string, c with -1 value
  • Iterate using i till the length of list s
  • For each iteration check if i< c. If the condition is true move to the next iteration else move to the else part.
  • If the above condition is false Initialize k to zero. Check the condition if s[i] is equal to s1[k] and i+len(s1) is less than or equal to length of s. If true then initialize z to zero.
  • Use nested for loop using the j variable from i to length of s +1.  For each iteration initialize z to j.  Check the condition if s[j] is not equal to s1[k]. If true we will come out of this loop else we will increase k by 1.
  • If z is equal to i+length(s1)-1 then append s2 at the end of ans variable. Assign c value of i+len(s1). Else append s at the end of ans variable
  • Else append s[i] at the end of ans variable
  • Return ans variable.

Python Code

Run 
def modifyString(s, s1, s2):
    ans = ""
    c = -1
    for i in range(len(s)):
        if i < c:
            continue
        k = 0
        if s[i] == s1[k] and i + len(s1) <= len(s):
            z = 0
            for j in range(i, i + len(s1)):
                z = j
                if s[j] != s1[k]:
                    break
                else:
                    k += 1

            if z == i + len(s1) - 1:
                ans += s2
                c = i + len(s1)
            else:
                ans += s[i]
        else:
            ans += s[i]

    return ans


s = "Let's Learn Python from Internet"
s1 = "Internet"
s2 = "PrepInsta"
print("Original String :", s)
print("Modified String :", modifyString(s, s1, s2))

Output:

Original String : Let's Learn Python from Internet
Modified String : Let's Learn Python from PrepInsta

Method 2:

In-Built Function

As you know Python is one of the most simple programming languages. Python has an In-Built Function “replace” for strings. For which we don’t even require any additional libraries. Let’s see how to use it:

Replace Function Format  :-  a.replace(b, c)

  • a – Sentence in which you want to replace the word
  • b – Word you want to replace from a
  • c – Word which is supposed to replace b

Python Code

Run 
s = "Let's Learn Python from Internet"
s1 = "Internet"
s2 = "PrepInsta"

x = s.replace(s1, s2)

print("Original String :", s)
print("Modified String :", x)

Output:

Original String : Let's Learn Python from Internet
Modified String : Let's Learn Python from PrepInsta

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