What is the difference between python `is` and `==`?
Jul 12, 2025 am 02:08 AMIn Python, == compares values while 'is' checks memory identity. 1. == evaluates if two objects have equal values, like a == b for lists with same elements. 2. 'is' determines if two variables reference the exact same object in memory, which is why a is b returns False for separate lists. 3. Use == for value comparisons and 'is' only for checking None or confirming identical object references. 4. Be cautious as small integers and strings may be interned, causing unexpected 'is' results, but this behavior is implementation-dependent and unreliable for general use.
The difference between is
and ==
in Python is pretty straightforward once you understand what each one actually checks. In short:

-
==
compares the values of two objects. -
is
compares the identities (memory addresses) of two objects.
So even if two variables have the same value, they might not be the same object in memory — which means ==
could return True
while is
returns False
.
How ==
Works – Value Comparison
When you use ==
, Python checks whether the values of the two operands are equal. This can sometimes involve a lot of behind-the-scenes logic depending on the type of object, especially for custom classes that override equality behavior.

Examples:
a = [1, 2, 3] b = [1, 2, 3] print(a == b) # True – same values
Even though a
and b
are separate lists, their contents are identical, so ==
returns True
.

Another example:
x = "hello" y = "hello" print(x == y) # True – both strings have the same characters
This works because immutable types like strings and small integers are often cached or interned by Python, which can affect how is
behaves — more on that next.
How is
Works – Identity Comparison
The is
operator doesn't care about the values — it only checks whether two variables refer to the exact same object in memory.
Using the same list example:
a = [1, 2, 3] b = [1, 2, 3] print(a is b) # False – different objects in memory
But if you assign b = a
, then they point to the same object:
a = [1, 2, 3] b = a print(a is b) # True – same object
Now any changes made through a
will also appear in b
, since they reference the same list.
When Should You Use Each?
Use these rules of thumb:
- Use
==
when comparing values. That’s almost always what you want. - Use
is
only when checking againstNone
, or when you really need to confirm two names point to the same object.
Examples where is
makes sense:
value = None if value is None: print("Value is missing")
Avoid doing this:
x = 5 if x is 5: # Not reliable! print("Yes")
Because for integers and other types, interning may or may not happen — it's implementation-dependent.
Also avoid comparing strings with is
:
s = "hello" if s is "hello": # Don't rely on this pass
Again, string interning varies and shouldn't be trusted unless you're certain.
Some Gotchas to Watch For
Here are a few common surprises people run into:
Small integers are interned:
a = 256 b = 256 print(a is b) # True
But bigger numbers aren’t:
a = 257 b = 257 print(a is b) # False
Strings with special characters or longer ones may not be interned either.
Lists, dicts, and sets are never interned:
a = {} b = {} print(a is b) # False
These behaviors show why relying on
is
for general comparisons is risky.
So yeah, basically
==
checks if things are alike in value, andis
checks if they’re literally the same thing in memory. Most of the time, you’ll stick with==
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