What does hash do in python?

Question

I saw an example of code that where hash function is applied to a tuple. As a result it returns a negative integer. I wonder what does this function do? Google

Answer 1

The Python docs for hash() state:

Hash values are integers. They are used to quickly compare dictionary keys during a dictionary lookup.

Python dictionaries are implemented as hash tables. So any time you use a dictionary, hash() is called on the keys that you pass in for assignment, or look-up.

Additionally, the docs for the dict type state:

Values that are not hashable, that is, values containing lists, dictionaries or other mutable types (that are compared by value rather than by object identity) may not be used as keys.