What happens under the hood when adding an element to a dictionary?

When an element is added to a dictionary (dict) in Python, the following occurs:

1. The hash of the key is computed — the __hash__ function of the key is called.
2. The index in the hash table is determined — the position in the array is calculated based on the hash.
3. The cell occupancy is checked:
   • If the cell is free, the element is inserted.
   • If it is occupied, collision resolution occurs (in CPython, open addressing with probing is used).
4. If the load factor of the table exceeds a threshold, the hash table is resized and elements are redistributed.

Thus, adding an element involves inserting a key-value pair into the hash table with collision control and dynamic resizing to maintain performance.