In-depth look into Python datatypes (1)

Python data model

• Python data model is a description of Python as a framework
• It formalizes the interfaces of the building blocks of the language itself, such as sequences, iterators, functions, classes, context managers and so on
• It is based on the so called special methods (or magic methods)
• The Python interpreter invokes special methods to perform basic object operations, often triggered by special syntax.
• Special methods are always spelled with leading and trailing double underscores

Examples:

__init__ # constructor
__repr__ # representation ()
__str__ # string representation (print)
__add__ # addition

__len__ # length
__iter__ # iteration
__getitem__ # indexing
__contains__ # membership

Usage of special methods:

len(my_object) # calls my_object.__len__()
my_object[0] # calls my_object.__getitem__(0)
my_object in my_collection # calls my_collection.__contains__(my_object)
for item in my_object: # calls iter(my_object), which in turn calls my_object.__iter__()

Resources:

• https://www.fluentpython.com/extra/internals-of-sets-and-dicts/
• https://pythontutor.com/