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# Python | K length Padding in List

• Last Updated : 19 Feb, 2020

In real world problems, we sometimes require to pad the element of list according to a condition that maximum characters have reached. Padding a number with 0 if it’s length is less than required by any field is one of the basic issues that occur in web forms in Web Development. Let’s discuss certain ways in which this issue can be solved.

Method #1 : Using list comprehension
This problem can be solved easily using the basic list comprehension in which we just need to use string formatting to perform the optional padding with 0 if size of each element is less than the specified size.

 `# Python3 code to demonstrate ``# K length Padding in List``# using list comprehension`` ` `# initializing list ``test_list ``=` `[``3``, ``54``, ``4``, ``100``, ``10``]`` ` `# printing original list``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing K ``K ``=` `4`` ` `# using list comprehension``# K length Padding in List``temp ``=` `"% 0"` `+` `str``(K) ``+` `"d"``res ``=` `[temp ``%` `i ``for` `i ``in` `test_list]`` ` `# printing result ``print` `(``"The list after K size element padding : "` `+` `str``(res))`

Output :

```The original list is : [3, 54, 4, 100, 10]
The list after K size element padding ['0003', '0054', '0004', '0100', '0010']
```

Method #2 : Using `str.rjust()`
There is a function dedicated in python to do this job. The rjust function does the task of specifying the size of the string and also takes the character in which the character has to be padded.

 `# Python3 code to demonstrate ``# K length Padding in List``# using str.rjust()`` ` `# initializing list ``test_list ``=` `[``3``, ``54``, ``4``, ``100``, ``10``]`` ` `# printing original list``print` `(``"The original list is : "` `+` `str``(test_list))`` ` `# initializing K ``K ``=` `4`` ` `# using str.rjust()``# to perform list element padding``res ``=` `[``str``(i).rjust(K, ``'0'``) ``for` `i ``in` `test_list]`` ` `# printing result ``print` `(``"The list after K size element padding : "` `+` `str``(res))`

Output :

```The original list is : [3, 54, 4, 100, 10]
The list after K size element padding ['0003', '0054', '0004', '0100', '0010']
```

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