# Python | Type casting whole List and Matrix

Sometimes, while working with Python List or Matrix, we usually have a problem in which we require to get a generalized function which could perform the type casting of whole container at once. There is always a need of a mechanism code which can transform entirely the allowed change of data type for all elements in container. Let’s discuss a way in which this task can be performed.

Method : Using `map()` + list comprehension
This task can be performed using a map(). The transformation of a normal list can be performed using a single map function by just passing the desired data type. But when it comes to transformation of whole matrix, we need the help of list comprehension for the same.

 `# Python3 code to demonstrate working of ` `# Type casting whole List and Matrix ` `# using map() + list comprehension ` ` `  `# helper function to type cast list  ` `def` `cast_list(test_list, data_type): ` `    ``return` `list``(``map``(data_type, test_list)) ` `     `  `# helper function to type cast Matrix  ` `def` `cast_matrix(test_matrix, data_type): ` `    ``return` `list``(``map``(``lambda` `sub: ``list``(``map``(data_type, sub)), test_matrix)) ` `     `  `# initialize list  ` `test_list ``=` `[``1``, ``4``, ``9``, ``10``, ``19``] ` ` `  `# initialize Matrix ` `test_matrix ``=` `[[``5``, ``6``, ``8``], [``8``, ``5``, ``3``], [``9``, ``10``, ``3``]] ` ` `  `# printing original list ` `print``(``"The original list is : "` `+` `str``(test_list)) ` ` `  `# printing original matrix ` `print``(``"The original Matrix is : "` `+` `str``(test_matrix)) ` ` `  `# Type casting whole List and Matrix ` `# using map() + list comprehension ` `res_list ``=` `cast_list(test_list, ``str``) ` `res_matrix ``=` `cast_matrix(test_matrix, ``str``) ` ` `  `# printing result ` `print``(``"The List after type casting is : "` `+` `str``(res_list)) ` `print``(``"The Matrix after type casting is : "` `+` `str``(res_matrix)) `

Output :

```The original list is : [1, 4, 9, 10, 19]
The original Matrix is : [[5, 6, 8], [8, 5, 3], [9, 10, 3]]
The List after type casting is : ['1', '4', '9', '10', '19']
The Matrix after type casting is : [['5', '6', '8'], ['8', '5', '3'], ['9', '10', '3']]
```
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