Given a string of words. The task is to write a Python program to replace the given word irrespective of the case with the given string.
Examples
Input : String = "gfg is BeSt", replace = "good", substring = "best"
Output : gfg is good
Explanation : BeSt is replaced by "good" ignoring cases.
Case insensitive string replacement using re.IGNORECASE + re.escape() + re.sub()
In this, sub() of the regex is used to perform the task of replacement, and IGNORECASE ignores the cases and performs case-insensitive replacements.
Python3
import re# initializing stringtest_str = "gfg is BeSt"# printing original stringprint("The original string is : " + str(test_str))# initializing replace string repl = "good"# initializing substring to be replaced subs = "best"# re.IGNORECASE ignoring cases # compilation step to escape the word for all casescompiled = re.compile(re.escape(subs), re.IGNORECASE)res = compiled.sub(repl, test_str) # printing resultprint("Replaced String : " + str(res)) |
Output
The original string is : gfg is BeSt
Replaced String : gfg is good
Case insensitive string replacement using re.sub() + lambda + re.escape()
Using particular ignore case regex also this problem can be solved. Rest, a lambda function is used to handle escape characters if present in the string.
Python3
import re# initializing stringtest_str = "gfg is BeSt"# printing original stringprint("The original string is : " + str(test_str))# initializing replace string repl = "good"# initializing substring to be replaced subs = "best"# regex used for ignoring casesres = re.sub('(?i)'+re.escape(subs), lambda m: repl, test_str) # printing resultprint("Replaced String : " + str(res)) |
Output
The original string is : gfg is BeSt
Replaced String : gfg is good
Case insensitive string replacement using split(), lower() and string replace()
Here, you can also use upper() in place of lower().
Python3
# initializing stringtest_str = "gfg is BeSt"# printing original stringprint("The original string is : " + str(test_str))# initializing replace stringrepl = "good"# initializing substring to be replacedsubs = "best"x = test_str.split()for i in x: if(i.lower()==subs.lower()): test_str=test_str.replace(i,repl)# printing resultprint("Replaced String : " + test_str)#contributed by Bhavya Koganti |
Output
The original string is : gfg is BeSt
Replaced String : gfg is good
Time Complexity: O(n), where n is length of test_str.
Auxiliary Space: O(1)
Case insensitive string replacement using a List and Join()
Strings are not directly mutable so using lists can be an option. And then get back the string using join on the list.
Python3
# the given input string.test_str = "gfg is BeSt"# the replace string.repl = "good"# the string to be replaced.subs = "best"# create the list.l = test_str.split(" ")# loop and replace the target string.for i, w in enumerate(l): if w.lower() == subs: l[i] = repl# list to string using join.output = " ".join([i for i in l])print("The original string is :", test_str)print("Replaced String :", output) |
The original string is : gfg is BeSt Replaced String : gfg is good
Time Complexity: O(n), where n is
Auxiliary Space: O(1)
Case insensitive string replacement using Regular Expression
In Python, we can use regular expressions for case-sensitive string replacement.
Python3
import re# the given input string.test_str = "gfg is BeSt"# the replace string.repl = "good"# the string to be replaced.subs = "best"def replace_substring(test_str, repl, subs): # Replacing all occurrences of substring s1 with s2 test_str = re.sub(r'(?i)'+subs, repl, test_str) return test_strprint("The original string is :", test_str)print("Replaced String :", replace_substring(test_str, subs, repl)) |
The original string is : gfg is BeSt Replaced String : gfg is good
Time Complexity: O(n), where n is the length of the input string.
Auxiliary Space: O(1)
