为什么使用“==”或“is”比较字符串有时会产生不同的结果?

is ==

>>> a = 'pub'
>>> b = ''.join(['p', 'u', 'b'])
>>> a == b
True
>>> a is b
False

id(a) == id(b)

is ==

interned

is ==

>>> a = intern('a')
>>> a2 = intern('a')
>>> a is a2
True

is

sys

is ==

person

class Person(object):
   def __init__(self, name, age):
       self.name = name
       self.age = age

   def __eq__(self, other):
       return self.name == other.name and self.age == other.age

jack1 = Person('Jack', 23)
jack2 = Person('Jack', 23)

jack1 == jack2 #True
jack1 is jack2 #False

if x is None: 
    # some clauses

there is guaranteed to be one instance of the Null Object (i.e., None)

>>> a = 1
>>> b = 1
>>> b is a
True
>>> a = 6000
>>> b = 6000
>>> b is a
False

is ==

>>> s1 = u'public'
>>> s2 = 'public'
>>> s1 is s2
False
>>> s1 == s2
True

s1 s2

== is

>>> s = 'one'
>>> s2 = 'two'
>>> s is s2
False
>>> s2 = s2.replace('two', 'one')
>>> s2
'one'
>>> s2 is s
False
>>> 

s

== is

>>> a = 'banana'
>>> b = 'banana'
>>> a is b 
True

a b

>>> a = 'a longer banana'
>>> b = 'a longer banana'
>>> a == b, a is b
(True, False)

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

b = a

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

is == Python Documentation

a is b a == b

>>> nan = float('nan')
>>> nan is nan
True
>>> nan == nan
False

is

==

s1='public'
s2='public'
sorted(s1) == sorted(s2)

TRUE

s1='public'
s2='publci'
sorted(s1) == sorted(s2)

s1='public'
s2='publca'
sorted(s1) == sorted(s2)

FALSE