How would I detect insertion of the same key with a different value into a dict?

Question

So my goal for this problem is to, given 2 strings, str1 and str2, create a dictionary such that the characters in str1 are the keys and the corresponding characters in str2 are the values.

ie. crackthecode('apple','byytr') returns {'a':'b','p':'y','l':'t','e':'r'} and if it is inconsistent, ie. crackthecode('apple','byptr') then returns {}, an empty dictionary.

This is my code, I'm just not sure how to do the inconsistent case.

PS. I cannot use zip for this question.

Below is my code.

def crackthecode(str1, str2):
  final = {}
  x = 0
  for i in list(str1):
    final[i]=str2[x]
    x = x + 1
  return final

All help is appreciated, thanks!

what do u mean by 2 of the same keys? dict keys are unique and immutable! — Amitkumar Karnik, Nov 20 '19 at 04:44
@AmitKarnik. While the title is a bit misleading, the question itself explains quite well what OP means — Mad Physicist, Nov 20 '19 at 04:50
@Sania. What would you do for `crackthecode('apple', 'xxxxx')`? — Mad Physicist, Nov 20 '19 at 04:58
@MadPhysicist In that case you would return the empty dictionary `{}` — Sania, Nov 20 '19 at 05:26
That's a good point. I guess each key would have the same value. — Sania, Nov 20 '19 at 18:05

Keyur Potdar · Answer 1 · 2019-11-22T07:05:36.517

2

You can check if the key is already present in the dictionary, and compare the value with the new character. If they are not equal, return an empty dictionary. Otherwise, add the key-value pair to the dictionary.

You can use this code which uses the EAFP principle.

>>> def crackthecode(str1, str2):
    final = {}
    for i, key in enumerate(str1):
        try:
            if final[key] != str2[i]:
                return {}
        except KeyError:
            final[key] = str2[i]
    return final

>>> crackthecode('apple','byytr')
{'a': 'b', 'p': 'y', 'l': 't', 'e': 'r'}
>>> crackthecode('apple','byptr')
{}

Edit: Same code without using enumerate (requested by OP)

def crackthecode(str1, str2):
    final = {}
    for i in range(len(str1)):
        try:
            if final[str1[i]] != str2[i]:
                return {}
        except KeyError:
            final[str1[i]] = str2[i]
    return final

edited Nov 22 '19 at 07:05

answered Nov 20 '19 at 04:44

Keyur Potdar

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Is there a way to do it without using enumerate? – Sania Nov 20 '19 at 05:27
You can simply use `for i in range(len(str1))` and change `key` to `str1[i]`. – Keyur Potdar Nov 20 '19 at 05:28
Changing key to str1[i] didn't seem to work for me, do you mind showing me what you tried? – Sania Nov 22 '19 at 00:37

How would I detect insertion of the same key with a different value into a dict?

1 Answers1