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Newsgroups: comp.lang.python
Date: Wed, 17 Apr 2013 21:29:57 -0700 (PDT)
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Subject: Re: Atoms, Identifiers, and Primaries
From: 88888 Dihedral <dihedral88888@googlemail.com>
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Ian=E6=96=BC 2013=E5=B9=B44=E6=9C=8817=E6=97=A5=E6=98=9F=E6=9C=9F=E4=B8=89U=
TC+8=E4=B8=8B=E5=8D=883=E6=99=8221=E5=88=8600=E7=A7=92=E5=AF=AB=E9=81=93=EF=
=BC=9A
> On Tue, Apr 16, 2013 at 8:57 PM, Bruce McGoveran
>=20
>  wrote:
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> > These are terms that appear in section 5 (Expressions) of the Python on=
line documentation.  I'm having some trouble understanding what, precisely,=
 these terms mean.  I'd appreciate the forum's thoughts on these questions:
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> >
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> > 1.  Section 5.2.1 indicates that an identifier occurring as an atom is =
a name.  However, Section 2.3 indicates that identifiers are names.  My que=
stion:  can an identifier be anything other than a name?
>=20
>=20
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> Yes.  For example:
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>=20
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> from a import b
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>=20
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> Here "a" is an identifier but not a name, as it does not carry
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> object-binding semantics.
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> > 2.  Section 5.3 defines primaries as the most tightly bound operations =
of Python.  What does this mean?
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>=20
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> "Tightly bound" here refers to operator precedence.  For example, we
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> say that the multiplication operator binds more tightly [to the
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> surrounding operands] than the arithmetic operator, because the
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> multiplication takes precedence.  This section defines that the most
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> tightly bound operations in Python are attribute references,
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> subscriptions, slices and calls; these always take precedence over
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> other neighboring operations.
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>=20
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> > In particular, if an atom is a primary, what operation is the atom perf=
orming that leads to the label "most tightly bound"?
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> An atom doesn't perform an operation.  The grammar defines that a
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> primary can be just an atom, so that anywhere in the grammar that
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> expects a primary, a simple atom with no primary operation performed
>=20
> on it can equally be used.

An atom can not be divided into further details.
An atom can be created and cloned or just referenced=20
in some relations.

An object is composed of atoms linked in someway.

Of course, one can box those atoms of an object=20
to make the object immutable at least in some situations
to be named and used.