When printing set continer in python 3, it prints it without order

Question

I'm just trying to learn set containers in python. So, I created a normal set using :

dset = set(['a','c','z','d'])

but when I print it, it results :

{'c', 'a', 'z', 'd'}

shouldn't it be :

{'a', 'c', 'z', 'd'}

Can anyone explain why the output is like this? Is there any default sort mechanism for set datatype? or is my math is weak?

sets are not ordered containers. If you want order you have to go with lists or tuples — Ma0, Oct 16 '18 at 07:11
so they'll always give this random ordered output everytime I print a newly created set? @Ev.Kounis — elpidaguy, Oct 16 '18 at 07:12
It could be that you get the same output if you run it over and over again but this output is not one you can count on getting. — Ma0, Oct 16 '18 at 07:15
I think [this](https://stackoverflow.com/questions/1653970/does-python-have-an-ordered-set) is what you want. There is a module in pypi [ordered-set](https://pypi.org/project/ordered-set/) — Albin Paul, Oct 16 '18 at 07:17
so I'll conclude that as set are unordered containers, It will randomly print the items in it. Not any logical explanation to it? am i correct? and Thanks! @Ev.Kounis — elpidaguy, Oct 16 '18 at 07:19
@exabytes.js - Because of their primary usage, there is no need for there to be an order and it assists performance. See [Python Sets vs Lists](https://stackoverflow.com/q/2831212/1324033) — Sayse, Oct 16 '18 at 07:21

U13-Forward · Accepted Answer · 2018-10-16T07:40:24.880

Sets are not ordered, they are not ordered containers, so nothing you can do,

If you have a list and you want to use set then convert back to list in ordered way:

print(sorted(set(l),key=l.index))

So no chance of making ordered set

Btw, there is a ordered set...

link to download file, or just copy the code in a module and import it, remember to remove the if __name__ == '__main__' part in the bottom

Or pip install boltons, then:

from boltons.setutils import IndexedSet

Then example:

>>> from boltons.setutils import IndexedSet
>>> x = IndexedSet(list(range(4)) + list(range(8)))
>>> x
IndexedSet([0, 1, 2, 3, 4, 5, 6, 7])
>>> x - set(range(2))
IndexedSet([2, 3, 4, 5, 6, 7])
>>> x[-1]
7
>>> fcr = IndexedSet('freecreditreport.com')
>>> ''.join(fcr[:fcr.index('.')])
'frecditpo'

See link

Or pip install sortedcontainers:

Once installed you can simply:

from sortedcontainers import SortedSet
help(SortedSet)

Or install collections_extended

Then example:

>>> from collections_extended import setlist
>>> sl = setlist('abracadabra')
>>> sl
setlist(('a', 'b', 'r', 'c', 'd'))
>>> sl[3]
'c'
>>> sl[-1]
'd'
>>> 'r' in sl  # testing for inclusion is fast
True
>>> sl.index('d')  # so is finding the index of an element
4
>>> sl.insert(1, 'd')  # inserting an element already in raises a ValueError
ValueError
>>> sl.index('d')
4

See link