Difference Between Variable and List Reference
Here, we will see the difference between variable and list reference.
Creating New Variable
In this example, we have created a new variable and will see about its reference. Here, value 10 gets stored in memory and its reference gets assigned to a.
Python3
a = 10 print ( " id of a : " , id ( 10 ) , " Value : " , a ) |
Output
id of a : 11094592 Value : 10
a
or
Modifying The Variable
In this example, we are modifying the variable and then comparing the reference after using + and += operators. Whenever we create or modify int, float, char, or string they create new objects and assign their newly created reference to their respective variables.
Python3
a = 10 # Assigning value to variable creates new object print ( " id of a : " , id (a) , " Value : " , a ) a = a + 10 # Modifying value of variable creates new object print ( " id of a : " , id (a) , " Value : " , a ) a + = 10 # Modifying value of variable creates new object print ( " id of a : " , id (a) , " Value : " , a ) |
Output
id of a : 11094592 Value : 10
id of a : 11094912 Value : 20
id of a : 11095232 Value : 30
But the same behavior is not seen in the list. In the below example, we can see that the reference remain same when we use + and += operator in the list.
Python3
a = [ 0 , 1 ] # stores this array in memory and assign its reference to a print ( "id of a: " , id (a) , "Value : " , a ) a = a + [ 2 , 3 ] # this will also behave same store data in memory and assign ref. to variable print ( "id of a: " , id (a) , "Value : " , a ) a + = [ 4 , 5 ] print ( "id of a: " , id (a) , "Value : " , a ) #But now this will now create new ref. instead this will modify the current object so # all the other variable pointing to a will also gets changes |
Output
id of a: 140266311673864 Value : [0, 1]
id of a: 140266311673608 Value : [0, 1, 2, 3]
id of a: 140266311673608 Value : [0, 1, 2, 3, 4, 5]
Python | a += b is not always a = a + b
In Python, a += b doesn’t always behave the same way as a = a + b, the same operands may give different results under different conditions. But to understand why they show different behaviors you have to deep dive into the working of variables. before that, we will try to understand the difference between Python Variable and List Reference in Python.
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