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Python program to concatenate Strings around K
  • Last Updated : 01 Oct, 2020

Given List of Strings, join all the strings which occurs around string K.

Input : test_list = [“Gfg”, “*”, “is”, “best”, “*”, “love”, “gfg”], K = “*” 
Output : [‘Gfg*is’, ‘best*love’, ‘gfg’] 
Explanation : All elements around * are joined.

Input : test_list = [“Gfg”, “$”, “is”, “best”, “$”, “love”, “gfg”], K = “$” 
Output : [‘Gfg$is’, ‘best$love’, ‘gfg’] 
Explanation : All elements around $ are joined. 
 

Method 1: Using a loop

This is a brute way in which this task can be performed. In this, we iterate through all the elements and check for K, if found we perform required concatenation with preceding and successive element.



Python3




# Python3 code to demonstrate working of
# Concatenate Strings on K String
# Using loop
  
# initializing list
test_list = ["Gfg""+", "is", "best", "+", "love", "gfg"]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K for Concatenate
K = "+"
  
res = []
idx = 0
  
while idx < len(test_list):
    
    ele = test_list[idx]
  
    # concatenation if next symbol is K
    if (idx < len(test_list) - 1) and test_list[idx + 1] == K:
        ele = ele + K + test_list[idx + 2]
  
        # increasing counter by 2
        idx += 2
    res.append(ele)
    idx += 1
  
# printing result
print("Strings after required concatenation : " + str(res))
Output
The original list is : ['Gfg', '+', 'is', 'best', '+', 'love', 'gfg']
Strings after required concatenation : ['Gfg+is', 'best+love', 'gfg']

 
Method 2 : Using join() + replace() + split()

The combination of the above functions can be used to solve this problem. In this, we perform joining of all elements and then remove space around target K. Being treated as a single string, splitting the required string produces joined values around K.

Python3




# initializing list
test_list = ["Gfg""+", "is", "best", "+", "love", "gfg"]
  
# printing original list
print("The original list is : " + str(test_list))
  
# initializing K for Concatenate
K = "+"
  
# performing split after removing space around K
# splits assuming Strings joined around K
res = ' '.join(test_list).replace(' ' + K + ' ', K).split()
  
# printing result
print("Strings after required concatenation : " + str(res))
Output
The original list is : ['Gfg', '+', 'is', 'best', '+', 'love', 'gfg']
Strings after required concatenation : ['Gfg+is', 'best+love', 'gfg']

 

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