why does dictionnary only print the last 3 items?

Question

d ={"A":"h","K":"h","Q":"h","A":"c","K":"c","Q":"c","A":"d","K":"d","Q":"d","A":"s","K":"s","Q":"s"}

print(d)

When I do this, it prints out:

{'A': 's', 'Q': 's', 'K': 's'}

How do I get to print out everything? I have trouble finding out how to write a dictionary with the same values on different keys.

Ok, so how would I create a dictionnary with Ah, As, Ac, Ad , Kh, Ks ... ? — VincFort, Jun 28 '16 at 14:36
The data structure you want is simply impossible. You need to change your idea of what data structure you want. — deceze, Jun 28 '16 at 14:38
Yeah check my answer @VincFort, you could use something like that. — RoadRunner, Jun 28 '16 at 15:09
It's possible to simulate having multiple identical keys in a Python dictionary, but it's really _not_ a very useful thing to do. Instead you should use a dictionary of lists or tuples, as shown in mrdomoboto's answer. But if you want to know how to do this weird trick, see [this answer](http://stackoverflow.com/a/38012975/4014959) I wrote recently. — PM 2Ring, Jun 28 '16 at 16:35

ospahiu · Accepted Answer · 2016-07-21T14:38:09.447

5

As others have mentioned in the comments, you cannot have duplicate key's in a dictionary, Python knows to update the existing key with the latest value it's been set to in the duplicate declarations.

You could have a Dictionary that has a tuple (immutable), or list (mutable) as its value.

So if you wanted to have the following coupled information:

'Ah', 'As', 'Ac', 'Ad' , 'Kh', 'Ks' ...

You could represent that data with:

d = { 'A' : ('h', 's', 'c', 'd'), 'K' : ('h', 's') }

A list value can also work if you wanted to mutate the data within the list. (or set if you do not want duplicate values)

d = { 'A' : ['h', 's', 'c', 'd'], 'K' : ['h', 's'] }

This way you have essentially factored out your common character to be your key.

edited Jul 21 '16 at 14:38

answered Jun 28 '16 at 14:47

ospahiu

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Personally I only know the word "collision" in the context of dicts/hashtables when two different keys have the same hash which is not the case here. Here equal keys are used and thus it is expected to replace the accosiated value, otherwise (`d = {}; d["a"] = "a"; d["a"] = "b"; print(d["a"]`) would not do what you expect (i.e. update "a"). So it is not a choice that python "removes duplicate keys" but the only possible thing. – syntonym Jun 28 '16 at 14:57
1

You are correct, however it's possible to fake duplicate keys in a `dict`: see the link in my comment on the question. – PM 2Ring Jun 28 '16 at 16:37
Interesting 'hack' technique @PM2Ring, I'll have to investigate that myself further! – ospahiu Jun 28 '16 at 16:42

RoadRunner · Answer 2 · 2016-06-28T15:39:34.360

You could have some other list data structure like this:

my_list = [["A", ["h", "c", "d", "s"]], ["K", ["h", "c", "d", "s"]], ["Q", ["h", "c", "d", "s"]]]

and maybe even convert it into a more usable dictionary, like this:

dic = {}

for item in my_list:
    key = item[0]
    value = item[1]
    dic[key] = value
print(dic)

Output:

{'Q': ['h', 'c', 'd', 's'], 'K': ['h', 'c', 'd', 's'], 'A': ['h', 'c', 'd', 's']}

why does dictionnary only print the last 3 items?

2 Answers2