Python appending dictionary, TypeError: unhashable type?

Question

abc = {}
abc[int: anotherint]

Then the error came up. TypeError: unhashable type? Why I received this? I've tried str()

Answer 1

This seems to be a syntax issue:

>>> abc = {}
>>> abc[1] = 2
>>> abc
{1: 2}
>>> abc = {1:2, 3:4}
>>> abc
{1: 2, 3: 4}
>>> 

At least the syntax of following is incorrect

abc[int: anotherint]

I guess you want to say

abc = [int: anotherint]

Which is incorrect too. The correct way is

abc = {int: anotherint}

unless abc is already defined in which case:

abc[int] = anotherint

is also a valid option.

Answer 2

There are two things wrong - first you have a logic error - I really don't think you want the slice of the dictionary between int (the type, which is unhashable [see below]) and the number anotherInt. Not of course that this is possible in python, but that is what you are saying you want to do.

Second, assuming you meant x[{int:anotherInt}]:

What that error means is that you can't use that as a key in a dictionary, as a rule python doesn't like you using mutable types as keys in dictionaries - it complicates things if you later add stuff to the dictionary or list... consider the following very confusing example:

x={}
x[x]=1

what would you expect this to do, if you tried to subscript that array which would you expect to return 1?

x[{}]
x[{x:x}]
x[{{}:x}]
x[x]

basicly when hashing mutable types you can either say, {} != {} with respect to hashes because they are stored in different places in memory or you end up with the weird recursive situation above

Answer 3

Since the title says appending and none of the answers provided a solution to append things to the dictionary I give it a try:

abc = {}
abc[1]= 2
abc['a'] = [3,9,27]
==> abc = {1:2, 'a':[3,9,27]}