:data:`~token.NAME` tokens represent *identifiers*, *keywords*, and

*soft keywords*.

Within the ASCII range (U+0001..U+007F), the valid characters for names

include the uppercase and lowercase letters (``A-Z`` and ``a-z``),

the underscore ``_`` and, except for the first character, the digits

``0`` through ``9``.

Names are composed of the following characters:

* uppercase and lowercase letters (``A-Z`` and ``a-z``),

* the underscore (``_``),

* digits (``0`` through ``9``), which cannot appear as the first character, and

* non-ASCII characters. Valid names may only contain "letter-like" and

"digit-like" characters; see:ref:`lexical-names-nonascii` for details.

Names must contain at least one character, but have no upper length limit.

Case is significant.

Besides ``A-Z``, ``a-z``, ``_`` and ``0-9``, names can also use "letter-like"

and "number-like" characters from outside the ASCII range, as detailed below.

All identifiers are converted into the `normalization form`_ NFKC while

parsing; comparison of identifiers is based on NFKC.

Formally, the first character of a normalized identifier must belong to the

set ``id_start``, which is the union of:

* Unicode category ``<Lu>`` - uppercase letters (includes ``A`` to ``Z``)

* Unicode category ``<Ll>`` - lowercase letters (includes ``a`` to ``z``)

* Unicode category ``<Lt>`` - titlecase letters

* Unicode category ``<Lm>`` - modifier letters

* Unicode category ``<Lo>`` - other letters

* Unicode category ``<Nl>`` - letter numbers

* {``"_"``} - the underscore

* ``<Other_ID_Start>`` - an explicit set of characters in `PropList.txt`_

to support backwards compatibility

The remaining characters must belong to the set ``id_continue``, which is the

union of:

* all characters in ``id_start``

* Unicode category ``<Nd>`` - decimal numbers (includes ``0`` to ``9``)

* Unicode category ``<Pc>`` - connector punctuations

* Unicode category ``<Mn>`` - nonspacing marks

* Unicode category ``<Mc>`` - spacing combining marks

* ``<Other_ID_Continue>`` - another explicit set of characters in

`PropList.txt`_ to support backwards compatibility

Unicode categories use the version of the Unicode Character Database as

included in the:mod:`unicodedata` module.

These sets are based on the Unicode standard annex `UAX-31`_.

See also:pep:`3131` for further details.

Even more formally, names are described by the following lexical definitions:

Formally, names are described by the following lexical definitions:

..grammar-snippet::

:group: python-grammar

NAME: `xid_start` `xid_continue`*

id_start: <Lu> | <Ll> | <Lt> | <Lm> | <Lo> | <Nl> | "_" | <Other_ID_Start>

id_continue: `id_start` | <Nd> | <Pc> | <Mn> | <Mc> | <Other_ID_Continue>

xid_start: <all characters in `id_start` whose NFKC normalization is

in (`id_start` `xid_continue`*)">

xid_continue: <all characters in `id_continue` whose NFKC normalization is

in (`id_continue`*)">

identifier: <`NAME`, except keywords>

NAME: `name_start` `name_continue`*

name_start: "a"..."z" | "A"..."Z" | "_" | <non-ASCII character>

name_continue: name_start | "0"..."9"

identifier: <`NAME`, except keywords>

A non-normative listing of all valid identifier characters as defined by

Unicode is available in the `DerivedCoreProperties.txt`_ file in the Unicode

Character Database.

.. _UAX-31:https://www.unicode.org/reports/tr31/

.. _PropList.txt:https://www.unicode.org/Public/17.0.0/ucd/PropList.txt

.. _DerivedCoreProperties.txt:https://www.unicode.org/Public/17.0.0/ucd/DerivedCoreProperties.txt

.. _normalization form:https://www.unicode.org/reports/tr15/#Norm_Forms

Note that not all names matched by this grammar are valid; see

:ref:`lexical-names-nonascii` for details.

.. _keywords:

:ref:`atom-identifiers`.

.. _lexical-names-nonascii:

Non-ASCII characters in names

Names that contain non-ASCII characters need additional normalization

and validation beyond the rules and grammar explained

:ref:`above<identifiers>`.

For example, ``ř_1``, ``蛇``, or ``साँप`` are valid names, but ``r〰2``,

``€``, or ``🐍`` are not.

This section explains the exact rules.

All names are converted into the `normalization form`_ NFKC while parsing.

This means that, for example, some typographic variants of characters are

converted to their "basic" form. For example, ``fiⁿₐˡᵢᶻₐᵗᵢᵒₙ`` normalizes to

``finalization``, so Python treats them as the same name::

..note::

Normalization is done at the lexical level only.

Run-time functions that take names as *strings* generally do not normalize

their arguments.

For example, the variable defined above is accessible at run time in the

:func:`globals` dictionary as ``globals()["finalization"]`` but not

``globals()["fiⁿₐˡᵢᶻₐᵗᵢᵒₙ"]``.

Similarly to how ASCII-only names must contain only letters, digits and

the underscore, and cannot start with a digit, a valid name must

start with a character in the "letter-like" set ``xid_start``,

and the remaining characters must be in the "letter- and digit-like" set

``xid_continue``.

These sets based on the *XID_Start* and *XID_Continue* sets as defined by the

Unicode standard annex `UAX-31`_.

Python's ``xid_start`` additionally includes the underscore (``_``).

Note that Python does not necessarily conform to `UAX-31`_.

A non-normative listing of characters in the *XID_Start* and *XID_Continue*

sets as defined by Unicode is available in the `DerivedCoreProperties.txt`_

file in the Unicode Character Database.

For reference, the construction rules for the ``xid_*`` sets are given below.

The set ``id_start`` is defined as the union of:

* Unicode category ``<Lu>`` - uppercase letters (includes ``A`` to ``Z``)

* Unicode category ``<Ll>`` - lowercase letters (includes ``a`` to ``z``)

* Unicode category ``<Lt>`` - titlecase letters

* Unicode category ``<Lm>`` - modifier letters

* Unicode category ``<Lo>`` - other letters

* Unicode category ``<Nl>`` - letter numbers

* {``"_"``} - the underscore

* ``<Other_ID_Start>`` - an explicit set of characters in `PropList.txt`_

to support backwards compatibility

The set ``xid_start`` then closes this set under NFKC normalization, by

removing all characters whose normalization is not of the form

``id_start id_continue*``.

The set ``id_continue`` is defined as the union of:

* ``id_start`` (see above)

* Unicode category ``<Nd>`` - decimal numbers (includes ``0`` to ``9``)

* Unicode category ``<Pc>`` - connector punctuations

* Unicode category ``<Mn>`` - nonspacing marks

* Unicode category ``<Mc>`` - spacing combining marks

* ``<Other_ID_Continue>`` - another explicit set of characters in

`PropList.txt`_ to support backwards compatibility

Again, ``xid_continue`` closes this set under NFKC normalization.

Unicode categories use the version of the Unicode Character Database as

included in the:mod:`unicodedata` module.

.. _UAX-31:https://www.unicode.org/reports/tr31/

.. _PropList.txt:https://www.unicode.org/Public/17.0.0/ucd/PropList.txt

.. _DerivedCoreProperties.txt:https://www.unicode.org/Public/17.0.0/ucd/DerivedCoreProperties.txt

.. _normalization form:https://www.unicode.org/reports/tr15/#Norm_Forms

..seealso::

*:pep:`3131` -- Supporting Non-ASCII Identifiers

*:pep:`672` -- Unicode-related Security Considerations for Python

.. _literals:

Literals