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Python | Repeating an item in a list

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Method # 1: Using List Comprehension
In this method, we simply loop twice for each value and add to the new list. This is just a concise alternative to the naive method.

# Python3 demo code
# duplicate the element
# using comprehension list

 
# initializing list

test_list = [ 4 , 5 , 6 , 3 , 9 ]

 
# print original list

pri nt ( "The original list is:" + str (test_list))

 
# using comprehension list
# duplicate element

res = [i for i in test_list for x in ( 0 , 1 )]

 
# print result

print ( "The list after element duplication" +   str (res))

Output:

 The original list is: [4, 5, 6, 3, 9] The list after element duplication [4, 4, 5 , 5, 6, 6, 3, 3, 9, 9] 

Method # 2: Using redu () + add
We can also use the Reduce function to use a function to simultaneously add a pair of similar numbers to the list.

# Python3 demo code
# duplicate the element
# using Reduce () + add

from operator import add

  
# initializing list

test_list = [ 4 , 5 , 6 , 3 , 9 ]

 
# print original list

print ( "The original list is:" + str (test_list))

 
# using Reduce () + add
# duplicate the element

res = list ( reduce (add, [(i, i) for i in test_list]))

 
# print result

print ( "The list after element duplication" +   str (res))

Output:

 The original list is: [4, 5, 6, 3, 9] The list after element duplication [4, 4, 5, 5, 6, 6, 3, 3, 9, 9] 

Method # 3: Using i tertools.chain (). from_iterable ()
The from_iterable function can also be used to accomplish this task of adding a duplicate. It just creates a pair of each repeating element and inserts it sequentially.

# Python3 demo code
# duplicate the element
# use itertools.chain.from_iterable ()

import itertools

 
# initialization list

test_list = [ 4 , 5 , 6 , 3 , 9 ]

  
# print original list

print ( "The original list is:" + str (test_list))

 
# using itertools.chain.from_iterable ()
# duplicate element

res = list (itertools.chain.from_iterable ([i, i] for i in test_list))

 
# print result

print (< / code> "The list after element duplication" +   str (res))

Output:

 The original list is: [4, 5, 6, 3, 9] The list after element duplication [4, 4, 5, 5, 6, 6, 3, 3, 9, 9] 

Python | Repeating an item in a list Python functions: Questions

Python | Repeating an item in a list repeat: Questions

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