# Python | Append Odd element twice

• Last Updated : 13 May, 2019

Given a list of number, the task is to create a new list from the initial list with the condition to append every odd element twice.

Below are some ways to achieve the above task.

Method #1: Using list comprehension

 `# Python code to create a new list from initial list``# with condition to append every odd element twice.`` ` `# List initialization``Input` `=` `[``1``, ``2``, ``3``, ``8``, ``9``, ``11``]`` ` `# Using list comprehension ``Output ``=` `[elem ``for` `x ``in` `Input` `for` `elem ``in` `(x, )``*``(x ``%` `2` `+` `1``)]`` ` `# printing ``print``(``"Initial list is:'"``, ``Input``)``print``(``"New list is:"``, Output)`

Output:

```Initial list is:' [1, 2, 3, 8, 9, 11]
New list is: [1, 1, 2, 3, 3, 8, 9, 9, 11, 11]
```

Method #2: Using itertools

 `# Python code to create a new list from initial list``# with condition to append every odd element twice.``  ` `# Importing``from` `itertools ``import` `chain``  ` `# List initialization``Input` `=` `[``1``, ``2``, ``3``, ``8``, ``9``, ``11``]``  ` `# Using list comprehension  and chain``Output ``=` `list``(chain.from_iterable([i] ``              ``if` `i ``%` `2` `=``=` `0` `else` `[i]``*``2` `for` `i ``in` `Input``))``  ` `# printing ``print``(``"Initial list is:'"``, ``Input``)``print``(``"New list is:"``, Output)`

Output:

```Initial list is:' [1, 2, 3, 8, 9, 11]
New list is: [1, 1, 2, 3, 3, 8, 9, 9, 11, 11]
```

Method #3: Using Numpy array

 `# Python code to create a new list from initial list``# with condition to append every odd element twice.`` ` `# Importing``import` `numpy as np`` ` `# List initialization``Input` `=` `[``1``, ``2``, ``3``, ``8``, ``9``, ``11``]``Output ``=` `[]`` ` `# Using Numpy repeat``for` `x ``in` `Input``:``    ``(Output.extend(np.repeat(x, ``2``, axis ``=` `0``))``      ``if` `x ``%` `2` `=``=` `1` `else` `Output.append(x))`` ` `# printing ``print``(``"Initial list is:'"``, ``Input``)``print``(``"New list is:"``, Output)`

Output:

```Initial list is:' [1, 2, 3, 8, 9, 11]
New list is: [1, 1, 2, 3, 3, 8, 9, 9, 11, 11]
```

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