Why does the “is” keyword have a different behavior when there is a dot in the string?

Question

Consider this code:

>>> x = \"google\"
>>> x is \"google\"
True
>>> x = \"google.com\"
>>> x is \"google.com\"
False
>         


        

Answer 1

"is" is an identity test. Python has some caching behavior for small integers and (apparently) strings. "is" is best used for singleton testing (ex. None).

>>> x = "google"
>>> x is "google"
True
>>> id(x)
32553984L
>>> id("google")
32553984L
>>> x = "google.com"
>>> x is "google.com"
False
>>> id(x)
32649320L
>>> id("google.com")
37787888L