Shift dictionary values and swap them but not randomly

Question

Dictionary I am starting with is:

s={'A' : 'A', 'B' : 'B', 'C' : 'C'}

Dictionary I want to end up with is:

{'A' : 'B', 'B' : 'C', 'C' : 'A'}.

The only thing I know is how to get random letters instead of the one I have on some particular position, but in this problem I have to shift key's values by n=1.

I have tried to define n by which values are shifted but I end up with an error.

import string
dictionary = dict.fromkeys(string.ascii_lowercase, 0)

def shift(dictionary,s)
    s2=' '
    for c in s:
          n=ord(c) - 65
          n=+=1
          n%=26
          s2+=chr(n+65)
    return s2

What version of python? Dictionaries are [not ordered before version 3.6](https://stackoverflow.com/questions/39980323/are-dictionaries-ordered-in-python-3-6/39980744). Are you relying on sorting the keys by alphabetical order? — pault, Apr 03 '19 at 17:18
how do you define "next". Is it by insertion order? Is it lexicographical order? — pault, Apr 03 '19 at 17:25
I have a strong suspicion that this is an [XY problem](http://xyproblem.info) and what you're actually looking for is `dict(zip(string.ascii_uppercase, string.ascii_uppercase[1:] + string.ascii_uppercase[0]))` — pault, Apr 03 '19 at 17:39

Arkistarvh Kltzuonstev · Answer 1 · 2019-04-03T17:30:23.620

2

If you're using python 3.6+, then try this :

from collections import deque
s={'A' : 'A', 'B' : 'B', 'C' : 'C'}
rotated_values = deque(s.values())
rotated_values.rotate(-1)
new_s = {k:v for k,v in zip(s, rotated_values)}

OUTPUT :

{'A': 'B', 'B': 'C', 'C': 'A'}

edited Apr 03 '19 at 17:30

answered Apr 03 '19 at 17:26

Arkistarvh Kltzuonstev

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score 0 · Answer 2 · answered Apr 03 '19 at 17:25

You should be using OrderedDict's to ensure that your dictionary retains it's ordering when iterating.

from collections import OrderedDict
input_dictionary = OrderedDict(A="A", B="B", C="C")
values = list(input_dictionary.values())
for index, key in enumerate(iter(input_dictionary.keys())):
    new_value_index = (index + 1) % len(values)
    input_dictionary[key] = values[new_value_index]
print(input_dictionary)

Which gives you OrderedDict([('A', 'B'), ('B', 'C'), ('C', 'A')])

Hope that helps

Shift dictionary values and swap them but not randomly

2 Answers2