How to modify a list while iterating through it in Python?

I have a list of elements and my task is to remove, add or update its items through a loop.I need to work on a project that involves working with lists of decimal numbers. To ensure that my program runs efficiently and effectively modifies the lists, I must carefully select appropriate coding statements and functions like Loops. It’s crucial that I pay close attention to computational performance to avoid any negative impact on the program’s functionality.

For Example:

my_list = [ 23, 45, 68, 89]
which loop?

Can someone suggest me ways of modifying list while iterating? Which Python Loop will be efficient to use for or while?