In Python, == and is used differently. 1. == is used to compare whether the values of two objects are equal, and is suitable for most scenarios where data content consistency is required; 2. is is used to check whether two variables point to the same object in memory, mainly used for identity recognition, such as checking whether it is None. For example, two lists with the same content return True using ==, but using is to return False. Therefore, the appropriate operator should be selected according to the needs: use == to determine whether the values are the same, and use is to determine whether it is the same object.
In Python, ==
and is
both used for comparison, but they do very different things. The short version is:

-
==
checks if two values are equal. -
is
checks if two references point to the exact same object in memory.
That means even if two variables look the same (same value), they might not be the same object — and that's where is
and ==
behave differently.
When to use ==
Use ==
when you want to compare the values of two objects. This is what most people expect when checking equality.

For example:
a = [1, 2, 3] b = [1, 2, 3] print(a == b) # True
Even though a
and b
are two separate lists, their contents are the same, so ==
returns True
.

This works with strings, numbers, dictionaries, and basically any time you care about the data being the same, not the identity of the object.
When to use is
Use is
when you want to check if two variables refer to the exact same object . It's comparing identities, not values.
Going back to the previous example:
a = [1, 2, 3] b = [1, 2, 3] print(a is b) # False
Here, a
and b
are two different list objects in memory, even though they contain the same values. So is
returns False
.
A common use case for is
checking against None
, because there's only one instance of None
in Python:
value = get_data() if value is None: print("No data returned")
This is the recommended way to test for None
, since it's faster and more explicit than using ==
.
Gotchas and surprises
Python sometimes reuses small integers or short strings to save memory. That can make is
seem like it works when it really shouldn't be used.
For example:
a = 100 b = 100 print(a is b) # Might return True a = 1000000 b = 1000000 print(a is b) # Probably returns False
This behavior depends on Python's internal optimizations and shouldn't be relied on.
Other cases to watch out for:
- Using
is
to compare booleans (True is True
is fine, but again, don't rely on it) - Comparing empty containers (
[] == []
isTrue
, but[] is []
isFalse
) - Mutable vs immutable types behaving differently under certain conditions
So just remember:
- Use
==
when comparing values. - Use
is
only when checking identity, especially forNone
.
Summary
To recap:
-
==
compares values. -
is
compared identities (whether two references point to the same object). - Only use
is
for identity checks, especially withNone
. - Don't assume small values or strings will always share identity.
Basically that's it.
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