['xxxxxxn', 'xxxxxxn', 'xxxxxxn', 'xxxxxxn', 'xxxxxx   n', 'xxxxxxn',
 '    xxxxxx   n', 'xxxxxx   n', 'xxxxxxn', ...]

AttributeError: 'list' object has no attribute 'strip'

[s.strip().title() for s in my_list]

a = ['xxxxxxn',  ' xxxxxx n', 'xxxxxx n', 'xxxxxxn', ...]
a = [x.strip().title() for x in a]

my_list=['xxxxxxn', 'xxxxxxn', 'xxxxxxn', 'xxxxxxn', 'xxxxxx   n', 'xxxxxxn', '    xxxxxx   n', 'xxxxxx   n', 'xxxxxxn']

def format_string_from_list(_str):
    return _str.strip().title()

my_new_list=[format_string_from_list(_str) for _str in my_list]
print my_new_list

>>> ['Xxxxxx', 'Xxxxxx', 'Xxxxxx', 'Xxxxxx', 'Xxxxxx', 'Xxxxxx', 'Xxxxxx', 'Xxxxxx', 'Xxxxxx']