What features should be considered when using numbers as keys?

When using numbers as keys in Python dictionaries, the following should be considered:

• Immutable: Numeric types (int, float, complex) are immutable, making them suitable for use as dictionary keys. The hash value of a number is stable and does not change during the lifetime of the object.
• Hashing: Python uses hashing for quick access to dictionary elements by key. Numbers have efficient hashing algorithms.
• Number types: While int and float can be keys, complex can also be used, but their use as keys is less common.
• Comparison: When comparing numeric keys, their value is considered. For example, 1 (int) and 1.0 (float) may be considered different keys due to their type, even if their numeric value matches. However, when searching for a key, Python does not automatically convert types. The key '1' (string) is different from 1 (number).

Example:

# int and float as keys
my_dict = {1: 'integer one', 1.0: 'float one', 2: 'integer two'}

# Access by key
print(my_dict[1])
print(my_dict[1.0])
# print(my_dict['1'])  # Error: KeyError