# Python – Subtract K from tuples list

• Last Updated : 27 Dec, 2019

Sometimes, while working with data, we can have a problem in which we need to perform update operation on tuples. This can have application across many domains such as web development. Let’s discuss certain ways in which subtraction of K can be performed.

Method #1 : Using list comprehension
This is shorthand to brute function that can be applied to perform this task. In this, we iterate for each element of each tuple to perform bulk subtraction of K of data.

 `# Python3 code to demonstrate working of``# Subtract K from tuples list``# Using list comprehension`` ` `# initialize list``test_list ``=` `[(``1``, ``3``, ``4``), (``2``, ``4``, ``6``), (``3``, ``8``, ``1``)]`` ` `# printing original list ``print``(``"The original list : "` `+` `str``(test_list))`` ` `# initialize add element``K ``=` `4`` ` `# Subtract K from tuples list``# Using list comprehension``res ``=` `[``tuple``(j ``-` `K ``for` `j ``in` `sub ) ``for` `sub ``in` `test_list]`` ` `# printing result``print``(``"List after subtraction of K : "` `+` `str``(res))`

Output :

```The original list : [(1, 3, 4), (2, 4, 6), (3, 8, 1)]
List after subtraction of K : [(-3, -1, 0), (-2, 0, 2), (-1, 4, -3)]
```

Method #2 : Using `map()` + lambda + list comprehension
The combination of above functions can be used to perform this task. In this, we just iterate for all elements using `map()` and extend logic of update using lambda function.

 `# Python3 code to demonstrate working of``# Subtract K from tuples list``# Using list comprehension + map() + lambda`` ` `# initialize list``test_list ``=` `[(``1``, ``3``, ``4``), (``2``, ``4``, ``6``), (``3``, ``8``, ``1``)]`` ` `# printing original list ``print``(``"The original list : "` `+` `str``(test_list))`` ` `# initialize add element``K ``=` `4`` ` `# Subtract K from tuples list``# Using list comprehension + map() + lambda``res ``=` `[``tuple``(``map``(``lambda` `ele : ele ``-` `K, sub)) ``for` `sub ``in` `test_list]`` ` `# printing result``print``(``"List after subtraction of K : "` `+` `str``(res))`

Output :

```The original list : [(1, 3, 4), (2, 4, 6), (3, 8, 1)]
List after subtraction of K : [(-3, -1, 0), (-2, 0, 2), (-1, 4, -3)]
```

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