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Understanding Python id() Function
The id() function in Python is a built-in function that provides you with a unique identifier for a given object. This identifier is an integer. This is guaranteed to be unique and constant for the object during its lifetime. Think of it like a memory address, although the specific interpretation can vary depending on your Python implementation. Python id() helps check if two variables refer to the same object in memory.
Syntax of Python id()
identity_number = id(object)
Explanation
identity_number: Variable stores unique integer.id(): Built-in function.object: Object whose ID you want.
Example of Python id()
my_string = "hello"
string_id = id(my_string)
print(string_id)Explanation
my_string = "hello": Assigns the string “hello”.string_id = id(my_string): Gets the unique ID ofmy_string.print(string_id): Displays integer.
Output
139934322073456
id() Parameters
The id() function takes a single parameter: the object whose unique identifier you want to retrieve. This object can be anything: a simple variable, a list, a function, or even a class. You only provide the object itself. Python id() then does the internal work to get the identifier.
Syntax
object_id = id(any_object)
Explanation
object_id: Variable to hold the returned ID.id(): Retrieves the unique identifier.any_object: The object.
Example
my_list = [1, 2, 3]
list_id = id(my_list)
print(list_id)Explanation
my_list = [1, 2, 3]: Creates list.list_id = id(my_list): Calls function to retrieve the ID ofmy_list.print(list_id): Prints the ID.
Output
139934322524864
id() Return Value
Python id() function provides a single integer value. This value represents the unique identity of the object you passed in as a parameter. Remember that this ID is only guaranteed to be unique during the object’s lifetime. Once an object is no longer used, its ID might be reused for another object later. Two objects with non-overlapping lifetimes may have the same id() value.
Syntax
unique_integer = id(object_in_question)
Explanation
unique_integer: Will store returned integer.id(): Python built-in function.object_in_question: Object which id need to be calculated.
Example
x = 10
identity = id(x)
print(identity)Explanation
x = 10: Assigns the value 10.identity = id(x): Obtains integer using theid()function.print(identity): Prints returned integer.
Output
139934588347696
Python id() for Inbuilt Datatypes
When you use Python id() with built-in data types like integers, strings, or floats, you’ll observe interesting behavior related to how Python manages these objects in memory. Python often uses a technique called “interning” for small integers and some strings. This means multiple variables with the same value point to the same object in memory, saving space. That is why their id() values will be identical.
Syntax
identifier = id(builtin_datatype_variable)
Explanation
identifier: This is the integer.id(): Function call.builtin_datatype_variable: Variable of type like int, string, float.
Example
a = 5
b = 5
print(id(a))
print(id(b))Explanation
a = 5andb = 5: Creates two variables with the same value.print(id(a)): Prints the ID ofa.print(id(b)): Prints the ID ofb.
Output
139934588347536
139934588347536
Python id() with Classes and Objects
When working with custom classes and objects in Python, id() provides the unique identity of each instance of your class. Each time you create a new object using your class, that object will have its unique ID. Even if two objects have the same attribute values, their IDs will differ as they are distinct instances residing in different memory locations.
Syntax
object_identity = id(instance_of_class)
Explanation
object_identity: Stores the ID.id(): Used to obtain the ID.instance_of_class: Object created from a custom class.
Example
class MyClass:
pass
obj1 = MyClass()
obj2 = MyClass()
print(id(obj1))
print(id(obj2))Explanation
class MyClass:: Defines a simple class.obj1 = MyClass()andobj2 = MyClass(): Creates two objects ofMyClass.print(id(obj1)): Prints the ID ofobj1.print(id(obj2)): Prints the ID ofobj2.
Output
139934322535536
139934322535600
Python id() with Sets
Sets are mutable collections of unique items in Python. Each set has a distinct identity as determined by Python ID (). If you create two sets, even if they initially contain the same elements, they will have different IDs. If you modify one set by adding or removing elements, its ID may remain the same or may change; it depends on the Python implementation.
Syntax
set_id = id(set_variable)
Explanation
set_id: Will store returned integer value.id(): Built-in function.set_variable: Set object.
Example
set1 = {1, 2, 3}
set2 = {3, 2, 1}
print(id(set1))
print(id(set2))Explanation
set1 = {1, 2, 3}andset2 = {3, 2, 1}: Creates two sets.print(id(set1)): Printsset1‘s ID.print(id(set2)): Printsset2‘s ID.
Output
139934322536128
139934322535872
Python id() with Tuples
Tuples, unlike sets, are immutable in Python. You can check their identity. If you create two tuples with identical elements in the same order, then it may or may not show the same ID; it depends because Python may return the same ID for optimization of small-sized tuples. Python id() confirms this behavior.
Syntax
tuple_id = id(tuple_variable)
Explanation
tuple_id: Stores the unique identifier.id(): Function to retrieve the ID.tuple_variable: Variable holding a tuple.
Example
tuple1 = (1, 2, 3)
tuple2 = (1, 2, 3)
print(id(tuple1))
print(id(tuple2))Explanation
tuple1 = (1, 2, 3)andtuple2 = (1, 2, 3): Initializes two tuples.print(id(tuple1)): Gets ID of thetuple1.print(id(tuple2)): Gets ID of thetuple2.
Output
139934322068864
139934322068864
Conclusion
Python id() function is used to get the unique identity of a Python object. The function takes one parameter: the object. The Python id() function return value is an integer. This integer is unique until the object is alive. You will become familiar with using Python id() with different datatypes.
