Question

I have a dictionary like

>>> x = {'a':2, 'c': 1, 'b':3}

There is no method available in dictionary to sort the dictionary by value. I sorted it using

>>> sorted_x = sorted(x.iteritems(), key=operator.itemgetter(1))
>>> sorted_x
[('c', 1), ('a', 2), ('b', 3)]

but now when I convert to sorted_x to dictionary again by using loop. like

>>> new_dict = {}
>>> for i in sorted_x:
    new_dict[i[0]] = i[1]
>>> new_dict
{'a': 2, 'c': 1, 'b': 3}

The new_dict again remains unsorted. Why the python dictionary cannot be sorted by key? can anyone shed light on it.

Answer 1

Dictionaries in python are hash maps. The keys are hashed in order to keep a fast access to the elements.

This means that internally the elements must be ordered depending on the hash they generate, not depending on the order you want to give.