Python Identity operators with variables and datastructures

Question

I have the following code:

a = []
b = a

when I compile the following code I get this:

print(b is a) --> True
print(b is []) --> False

if b = a then shouldn't b is [] return True?

is means referential equality, so that both things refer to the same object, two separate lists are not the same object. — willeM_ Van Onsem
– willeM_ Van Onsem, Commented Jul 31, 2019 at 21:46
Whether a literal produces a new object or refers to an existing object is basically an implementation detail. Don't use is with literals. — chepner
– chepner, Commented Jul 31, 2019 at 21:47
I should say, for immutable values it is an implementation detail. For mutable values, caching a value will cause problems. — chepner
– chepner, Commented Jul 31, 2019 at 21:48
Not all [] are the same object. [] is just an empty list, which can be constructed in many ways. — hpaulj
– hpaulj, Commented Jul 31, 2019 at 22:12

snamef · Accepted Answer · 2019-07-31 21:46:29Z

5

try that:

    a = []
b = a


print(id(a))
print(id(b))
print(id([]))

And you will see that a and b refers to the same object, while next [] is a different one. Check if b to see if b is not empty list

answered Jul 31, 2019 at 21:46

snamef

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