# Python – First Even Number in List

• Last Updated : 05 Feb, 2023

Sometimes, while working with lists, we can have a problem in which we need to extract certain numbers occurring first time. This can also be even number. This kind of problem is common in day-day and competitive programming. Lets discuss certain ways in which this task can be performed.

Method #1 : Using loop This is brute force way in which this task can be performed. In this, we loop through the list and when 1st time even number occurs, we store and break the loop.

## Python3

 `# Python3 code to demonstrate``# First Even Number in List``# using loop` `# Initializing list``test_list ``=` `[``43``, ``9``, ``6``, ``72``, ``8``, ``11``]` `# printing original list``print``("The original ``list` `is` `: " ``+` `str``(test_list))` `# First Even Number in List``# using loop``res ``=` `None``for` `ele ``in` `test_list:``    ``if` `not` `ele ``%` `2` `:``        ``res ``=` `ele``        ``break``    ` `# printing result``print` `("The first even element ``in` `list` `is` `: " ``+` `str``(res))`

Output :

```The original list is : [43, 9, 6, 72, 8, 11]
The first even element in list is : 6```

Method #2 : Using binary search (Sorted list) The binary search can also be employed on list when we have sorted list. In this, we keep looking for smaller even term when we find one and move to rear end in case we don’t find one.

## Python3

 `# Python3 code to demonstrate``# First Even Number in List``# using binary search` `# Initializing list``test_list ``=` `[``3``, ``7``, ``8``, ``9``, ``10``, ``15``]` `# printing original list``print``("The original ``list` `is` `: " ``+` `str``(test_list))` `# First Even Number in List``# using binary search``res ``=` `len``(test_list)``low ``=` `0``high ``=` `len``(test_list) ``-` `1``while` `low <``=` `high:``    ``mid ``=` `(low ``+` `high) ``/``/` `2``    ``if` `test_list[mid] ``%` `2``:``        ``low ``=` `mid ``+` `1``    ``else``:``        ``res ``=` `test_list[mid]``        ``high ``=` `mid ``-` `1``    ` `# printing result``print` `("The first even element ``in` `list` `is` `: " ``+` `str``(res))`

Output :

```The original list is : [3, 7, 8, 9, 10, 15]
The first even element in list is : 8```

## Python3

 `# Python3 code to demonstrate``# First Even Number in List``# using recursion``def` `findfirsteven(lst,i):``  ``if` `lst[i]``%``2``=``=``0``:``      ``return` `lst[i]``  ``else``:``      ``return` `findfirsteven(lst,i``+``1``)``  ``return` `-``1` `# Initializing list``test_list ``=` `[``43``, ``9``, ``6``, ``72``, ``8``, ``11``]` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))` `print` `(``"The first even element in list is : "` `+``str``( findfirsteven(test_list,``0``)))` `#This code is contributed by Vinay Pinjala`

Output

```The original list is : [43, 9, 6, 72, 8, 11]
The first even element in list is : 6```

Time Complexity:O(n)

Auxiliary Space: O(n)

Using filter function:

## Python3

 `# Python3 code to demonstrate``# First Even Number in List``# using filter function`` ` `# Initializing list``test_list ``=` `[``43``, ``9``, ``6``, ``72``, ``8``, ``11``]`` ` `# printing original list``print``(``"The original list is : "` `+` `str``(test_list))`` ` `# First Even Number in List``# using filter function``res ``=` `list``(``filter``(``lambda` `x: (x ``%` `2` `=``=` `0``), test_list))[``0``]`` ` `# printing result``print` `(``"The first even element in list is : "` `+` `str``(res))`

Output

```The original list is : [43, 9, 6, 72, 8, 11]
The first even element in list is : 6```

Time Complexity : O(n)

Auxiliary Space : O(n)

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