'''data0.py

   Jed Yang, 2016-11-12

   An example of destructive functions.
'''

print('Sorting using sorted()')

array = ['violet', 'daisy', 'ivy', 'rose']
print('input:', array)

result = sorted(array)
print('result:', result)
print()

# So far so good.

print('Sorting using .sort()')

array = ['violet', 'daisy', 'ivy', 'rose']
print('input:', array)

result = array.sort()
print('result:', result)
print()

# There are no errors reported, but why is it printing result: None?
# Hint: print the original array out to see what's going on.

# .sort() is a method that "destroys" what you had and changes it.  We say that
# it sorts "in-place."  We have discussed the benefit of sorting in-place: we
# do not need to create extra space to hold data.  (Imagine if the list is
# really, really long; do you want two copies of it?  Maybe not.)

# Python tries to remind you that .sort() sorts in-place by returning None.
# This is a feature, not a bug.  Indeed, if you are confused why you get None,
# you may then remember that you should just keep using 'array' instead, since
# it is now the sorted version of itself.  If Python had changed the list AND
# return the list, you may very well forget that the original list has been
# changed.

# You can try to print the original array in the first example after sorting to
# be sure that array was not changed when using sorted().