Find not working properly

[DeaD_EyE]

You should use the in operator.
The in operator looks up, if an object appears in a sequence.

In [26]: 's' in 'Andre'
Out[26]: False

In [27]: 's' in 'Sandra'
Out[27]: False

In [28]: 's' in 'Sandra'.lower()
Out[28]: True

With a list:

In [29]: l = [1,2,3]

In [30]: 5 in l
Out[30]: False

In [31]: 1 in l
Out[31]: True

With filter:

In [32]: list(filter(lambda x: 's' in x.lower(), ['Leon', 'Sucks', 'Mikes', 'Balls']))
Out[32]: ['Sucks', 'Mikes', 'Balls']

If you have one finite list and want to have a second list multiplied by 2, you should use a list comprehension:

list1 = [1,2,3]
list2 = [i*2 for i in list1]

You can use conditions in a list comprehension:

list1 = list(range(100))
list2 = [i*2 for i in list1 if i % 2 != 0]

I think the to filter with a list comprehension looks very natural and reads like an english sentence.
name for name in A_SEQUENCE if 's' in name.lower

In [33]: [name for name in ['Leon', 'Sucks', 'Mikes', 'Balls'] if 's' in name.lower()]
Out[33]: ['Sucks', 'Mikes', 'Balls']

The list-, set-, dict comprehension and generator expressions are very helpful.