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Comparision Operators, Python

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#1

num2 = 10
num3 = 10
list1 = [6,7,8]
list2 = [6,7,8]

print(num2 is not num3) # Both have the same object
print(list1 is list2) # Both have the different objects

OUTPUT: false
false

It shows false in both the print cases. I am not able to understand regarding the objects which has been mentioned in the comment part for explaining this output . Please elaborate the reason, how both the print cases are different in terms of object.
And also please clarify list1 = [6,7,8] & list2 = [6,7,8] are equal or not? I think if the order of the elements are different then the lists are said to be unequal otherwise if the order is same then it is said equal.

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#2

Hi @GIRIBALA_MAHANTO ,
Here, we see that num1 and num2 are integers of the same values, so they are equal as well as identical.

But list1 and list2 are lists. They are equal but not identical. It is because the interpreter locates them separately in memory although they are equal.

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#3

Hi @Ammar_Ahmad_Farid
If I am not wrong, are you saying that num1 and num2 point to same memory location , hence identical?

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#4

Both num1 and num2 have the same id’s while lists don’t have. You can check by running the below code.

num1=10

num2=10

print(id(num1)) #4303493760

print(id(num2)) #4303493760

list1 = [6,7,8]

list2 = [6,7,8]

print(id(list1)) #140598573294080

print(id(list2)) #140598841828800

The id() function returns a unique id for the specified object . All objects in Python has its own unique id. The id is assigned to the object when it is created.

Mutable objects are not same in Python.

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#5

So glad someone asked this question already. I still have questions about how these IDs get assigned. Why is it that the lists have different IDs but these strings have the same ID?

list1 = [6,7,8]
list2 = [6,7,8]
string1 = "Hello, World!"
string2 = "Hello, World!"

print(list1 is list2) # Both have the different objects
print(list1 == list2)

print(string1 is string2)
print(string1 == string2)

print(id(string1))
print(id(string2))

Yields:

False
True

True
True

139694609046024
139694609046024

Course: Learn Python 3 from Scratch - Free Interactive Course
Lesson: Comparison Operators - Learn Python 3 from Scratch

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#6

Hi, great question! I’m in the same boat now :smiley:
Did you find an answer to this?

Thanks

#7

Hi @Harry1

Each time we create a list in Python, a new object is created. So list1 and list2 are separate objects with different memory addresses, even though their contents are the same. That’s why list1 is list2 returns False . However, the comparison list1 == list2 checks if the contents of the lists are the same, and in this case, it returns True .

On the other hand, when we create a string in Python, there is a concept called string interning. It is a process of reusing the same string object in memory for multiple occurrences of the same string value.

In the above example, both string1 and string2 point to the same interned string object in memory. That’s why string1 is string2 returns True, indicating they are the same object. When you compare their values with string1 == string2, it also returns True because their contents are identical.

It’s important to note that string interning is an implementation detail of Python and may vary across different versions and implementations of the language.

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