# Is there a difference between "==" and "is"?

My Google-fu has actually failed me.

In Python, are the adhering to 2 examinations for equality matching?

n = 5
# Test one.
if n == 5:
print 'Yay!'

# Test two.
if n is 5:
print 'Yay!'


Does this apply for things where you would certainly be contrasting circumstances (a list claim)?

Okay, so this sort of solutions my question:

L = []
L.append(1)
if L == [1]:
print 'Yay!'
# Holds true, but...

if L is [1]:
print 'Yay!'
# Doesn't.


So == examinations value where is examinations to see if they coincide object?

629
2022-07-20 01:30:48
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They are entirely various . is look for object identification, while == look for equality (an idea that relies on both operands' kinds).

It is just a fortunate coincidence that "is" appears to function appropriately with tiny integers (as an example 5 = = 4+1). That is due to the fact that CPython optimizes the storage of integers in the range (-5 to 256) by making them singletons. This actions is entirely execution - reliant and also not assured to be maintained under all type of small transformative procedures.

As an example, Python 3.5 additionally makes brief strings singletons, yet cutting them interrupts this behavior:

>>> "foo" + "bar" == "foobar"
True
>>> "foo" + "bar" is "foobar"
True
>>> "foo"[:] + "bar" == "foobar"
True
>>> "foo"[:] + "bar" is "foobar"
False

22
2022-07-21 09:13:33
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Your solution is proper. The is driver contrasts the identification of 2 things. The == driver contrasts the values of 2 things.

An object is identification never ever transforms once it has actually been developed ; you might consider it as the object is address in memory.

You can regulate contrast practices of object values by specifying a __cmp__ method or a rich comparison method like __eq__.

8
2022-07-20 16:38:32
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is examinations for identity== examinations for equality

Each (tiny) integer value is mapped to a solitary value, so every 3 equals and also equivalent. This is an execution information, not component of the language specification though

13
2022-07-20 16:38:28
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== establishes if the values are equivalent, while is establishes if they are the specific very same object.

47
2022-07-20 16:37:58
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is will certainly return True if 2 variables indicate the very same object (in memory), == if the things described by the variables are equivalent.

>>> a = [1, 2, 3]
>>> b = a
>>> b is a
True
>>> b == a
True

# Make a new copy of list a via the slice operator,
# and assign it to variable b
>>> b = a[:]
>>> b is a
False
>>> b == a
True


In your instance, the 2nd examination just functions due to the fact that Python caches tiny integer things, which is an execution information. For bigger integers, this does not work:

>>> 1000 is 10**3
False
>>> 1000 == 10**3
True


The very same applies for string literals:

>>> "a" is "a"
True
>>> "aa" is "a" * 2
True
>>> x = "a"
>>> "aa" is x * 2
False
>>> "aa" is intern(x*2)
True


1086
2022-07-20 16:37:14
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