Difference in printing a function and calling a function involving Python Dictionaries

Asked Mar 20 '20 at 07:05

Active Mar 20 '20 at 09:30

Viewed 47 times

So I have a function that gives me the dictionary in the reverse the order of insertion.

a = {1:2, 2:5, 6:7}

def reverse_dict(dict): 
  reverse_list = list(reversed(list(dict.items())))

  di = {}

  for a, b in reverse_list: 
      di[a] = b 

  return di

However, If I call the function, my output is the same as the original dictionary but if i print it my output is the desired outcome.

print(reverse_dict(a))
>>> {6: 7, 2: 5, 1: 2}

reverse_dict(a)
>>> {1: 2, 2: 5, 6: 7}

Why is this happening and what is the fix ?

asked Mar 20 '20 at 07:05

Wu Daozi

2

I can't reproduce this behaviour from your example. – dspencer Mar 20 '20 at 07:09
are you getting the reversed dict in both of them are the normal dict in them ? – Wu Daozi Mar 20 '20 at 07:12
`>>> a {1: 2, 2: 5, 6: 7} >>> reverse_dict(a) {6: 7, 2: 5, 1: 2} >>> print(reverse_dict(a)) {6: 7, 2: 5, 1: 2}` Not so clear in the comment, but yes. It works as expected in both cases. – dspencer Mar 20 '20 at 07:13
2

I too can't reproduce. – Ch3steR Mar 20 '20 at 07:13
It is happening, I am working in Google Colab, maybe something to do with that ? – Wu Daozi Mar 20 '20 at 07:18
can't reproduce too... – Zhubei Federer Mar 20 '20 at 07:19
1

@WuDaozi Share your colab file. So we can look at it. – Ch3steR Mar 20 '20 at 07:20
1

as an aside, `list(reversed(list(dict.items())))` stop using `list` needlessly. `reversed(some_dict.items())` gives you a nice, efficient reversed iterator over the items in a dict. There is no need to create intermediate lists. – juanpa.arrivillaga Mar 20 '20 at 07:26
1

@juanpa.arrivillaga `reversed(dict.items())` will raise error saying `TypeError: 'dict_items' object is not reversible` in any python version less than 3.8. `reversed(dict.items())` works from python3.8 – Ch3steR Mar 20 '20 at 07:30
Which exact version of Python 3 are you using? – RemcoGerlich Mar 20 '20 at 09:37
The exact Python version is relevant here, because `dict` behavior changed in Python 3.6 and 3.7. See https://stackoverflow.com/a/39537308/674064 – das-g Mar 20 '20 at 09:44
@RemcoGerlich I am using python 3.6.9 – Wu Daozi Mar 20 '20 at 18:53

Difference in printing a function and calling a function involving Python Dictionaries

0 Answers0