Object introspection

Object introspection

Introspection: the ability to determine the type of an object at runtime.

One of Python’s strengths.

Everything in Python is an object and we can examine those objects.

dir

Returns a list of attributes and methods belonging to an object. Here is an example:

my_list = [1, 2, 3]
dir(my_list)
# Output: ['__add__', '__class__', '__contains__', '__delattr__', '__delitem__',
# '__delslice__', '__doc__', '__eq__', '__format__', '__ge__', '__getattribute__',
# '__getitem__', '__getslice__', '__gt__', '__hash__', '__iadd__', '__imul__',
# '__init__', '__iter__', '__le__', '__len__', '__lt__', '__mul__', '__ne__',
# '__new__', '__reduce__', '__reduce_ex__', '__repr__', '__reversed__', '__rmul__',
# '__setattr__', '__setitem__', '__setslice__', '__sizeof__', '__str__',
# '__subclasshook__', 'append', 'count', 'extend', 'index', 'insert', 'pop',
# 'remove', 'reverse', 'sort']

Introspection gave us the names of all the methods of a list.

dir() without any argument then it returns all names in the current scope.

type and id

type function returns the type of an object.

Example:

print(type(''))
# Output: <type 'str'>

print(type([]))
# Output: <type 'list'>

print(type({}))
# Output: <type 'dict'>

print(type(dict))
# Output: <type 'type'>

print(type(3))
# Output: <type 'int'>

id returns the unique ids of various objects.

Example:

name = "Yasoob"
print(id(name))
# Output: 139972439030304

inspect module

Provides several useful functions to get information about live objects.

Example: check the members of an object by running:

import inspect
print(inspect.getmembers(str))
# Output: [('__add__', <slot wrapper '__add__' of ... ...