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Python – Append given number with every element of the list
  • Last Updated : 26 Nov, 2020

Given a list and a number, write a Python program to append the number with every element of the list.

Examples:

input = [1,2,3,4,5]

key = 5 (number to be appended)

output = [1,5,2,5,3,5,4,5,5,5]



The following are ways to achieve this functionality:

Method 1: Using for loop

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input = [1, 2, 3, 4, 5]
key = 7
  
result = []
for ele in input:
    result.append(ele)
    result.append(key)
  
print(result)

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Output:

[1, 7, 2, 7, 3, 7, 4, 7, 5, 7]

Method 2: Using list comprehension and itertools.chain

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import itertools
  
input = [1, 2, 3, 4, 5]
key = 7
  
result = list(itertools.chain(*[[ele, key] for ele in input]))
  
print(result)

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Output:

[1, 7, 2, 7, 3, 7, 4, 7, 5, 7]

Method 3: Using zip and for loop

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input = [1, 2, 3, 4, 5]
key = 7
  
result = []
for x, y in zip(input, [key]*len(input)):
    result.extend([x, y])
  
print(result)

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Output:

[1, 7, 2, 7, 3, 7, 4, 7, 5, 7]

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