Apply function to each element of a list

Question

How do I apply a function to the list of variable inputs? For e.g. the filter function returns true values but not the actual output of the function.

Answer 1

Sometimes you need to apply a function to the members of a list in place. The following code worked for me:

>>> def func(a, i):
...     a[i] = a[i].lower()
>>> a = ['TEST', 'TEXT']
>>> list(map(lambda i:func(a, i), range(0, len(a))))
[None, None]
>>> print(a)
['test', 'text']

Please note, the output of map() is passed to the list constructor to ensure the list is converted in Python 3. The returned list filled with None values should be ignored, since our purpose was to convert list a in place