TypeError: unhashable type: 'list'

Question

bad_dict = {
([1, 2, 3]): "one two three"
}
print(bad_dict ([1, 2, 3]))

#i tried to make it a tuple to get immutable but got type error
#guys please tell me how to solve this error

Answer 1

https://code.sololearn.com/cjGq6M1HhSEW/?ref=app

Answer 2

A tuple can't contain a mutable object if it's used as a key ,all tuple elements should be immutable

Answer 3

A dictionary key must be hashable.
A hashable object has a hash value which never changes.
All strings and numerical values are hashable, sequences that are immutable are also hashable, but only if they contain hashable objects.
A list is not, it can be modified.
We can have a list inside a tuple, that tuple remains immutable but it won't be hashable.

https://code.sololearn.com/cL9nUvwMIc1t/?ref=app

Answer 4

Wow....the question becomes interesting

Answer 5

Rick Shiffman the *args in function signature is an unknown number of unnamed arguments, represented by a tuple. And you can even pass it lists, if you want.

def unpack(*args):
print(type(args))
for arg in args:
print(arg)

unpack("x", 42, [1, 0])

Answer 6

Oma Fall, and Abhay. Glad you posted the question, and Abhay's anwser. I had never thought about puting a mutible structure in tuple before. That kind of defeets reson for using a tupple and it makes sense that dictionary not be happy with a tupple a mutible sub-element in it.

By the way is there reason or use for a tupple with mutible sub-elements in it???

Answer 7

I want to point out that Ali gave the righter answer here.

It's not about the immutability.

You can create a class of your own and use (mutable) instances as keys for the dict.

https://www.sololearn.com/post/477553/?ref=app

Answer 8

thanks Tibor Santa, I sould have thought about that, since I wrote my own version of printf() for python. I feel dumb now

def printf( format, *vals ): #I like printf
sys.stdout.write( format % vals)

Answer 9

It solved thanks Abhay