Issue 25981: Intern namedtuple field names

If intern field names in namedtuple, this will speed up the access to them, because names could be compared just by identity in dict lookup. This can also make pickles containing namedtuples more compact.

Doesn't interning happen already as a byproduct of the exec?

Indeed, keys of __dict__ are interned. But elements of _fields are not.

>>> A = namedtuple('A', 'abc123 def456')
>>> sorted(A.__dict__)[-1] == A._fields[-1]
True
>>> sorted(A.__dict__)[-1] is A._fields[-1]
False

I don't see how the proposed patch would affect the result.  ISTM that the interning would have to happen after the template substitution and exec.  See the attached alternate patch.

That said, I'm not too concerned with the contents of _fields not being interned.  It isn't the performance sensitive part of the code.

Now, after you pointed out that the keys in the dictionary already interned, I'm not sure anymore that it is needed to intern the _fields items.

I'm wondering, why short identifier-like string literals in compiled _fields are not interned?

The benefits are tiny, but if the one line patch looks good, we might as well intern the _fields and save a few bytes.

Interesting, short string literals usually are interned, but they are not interned in tuple literal.

>>> namespace = {}
>>> exec('a = ["abc123"]\ndef abc123(): pass', namespace)
>>> namespace['abc123'].__name__ is namespace['a'][0]
True
>>> exec('a = ("abc123",)\ndef abc123(): pass', namespace)
>>> namespace['abc123'].__name__ is namespace['a'][0]
False
>>> namespace['abc123'].__name__ == namespace['a'][0]
True

I think it would be better to change the compiler to always intern short string literals. And patching namedtuple will be not needed.

> I think it would be better to change the compiler to always 
> intern short string literals. And patching namedtuple will 
> be not needed.

Can we close this entry?   If you do patch the compiler, a separate tracker item can be opened.

I already opened separate issue26148. Since I sure this is the correct way, I'm closing this issue. I'll reopen it in case of issue26148 will be rejected.

messages: + msg257247