diff options
Diffstat (limited to 'Doc/reference/lexical_analysis.rst')
| -rw-r--r-- | Doc/reference/lexical_analysis.rst | 55 |
1 files changed, 53 insertions, 2 deletions
diff --git a/Doc/reference/lexical_analysis.rst b/Doc/reference/lexical_analysis.rst index e1d88eff95..b197f23961 100644 --- a/Doc/reference/lexical_analysis.rst +++ b/Doc/reference/lexical_analysis.rst @@ -65,6 +65,7 @@ Comments -------- .. index:: comment, hash character + single: #; comment A comment starts with a hash character (``#``) that is not part of a string literal, and ends at the end of the physical line. A comment signifies the end @@ -78,6 +79,7 @@ Encoding declarations --------------------- .. index:: source character set, encoding declarations (source file) + single: #; source encoding declaration If a comment in the first or second line of the Python script matches the regular expression ``coding[=:]\s*([-\w.]+)``, this comment is processed as an @@ -349,6 +351,9 @@ exactly as written here: assert del global not with async elif if or yield +.. index:: + single: _, identifiers + single: __, identifiers .. _id-classes: Reserved classes of identifiers @@ -395,13 +400,16 @@ Literals Literals are notations for constant values of some built-in types. +.. index:: string literal, bytes literal, ASCII + single: '; string literal + single: "; string literal + single: u'; string literal + single: u"; string literal .. _strings: String and Bytes literals ------------------------- -.. index:: string literal, bytes literal, ASCII - String literals are described by the following lexical definitions: .. productionlist:: @@ -434,6 +442,8 @@ declaration; it is UTF-8 if no encoding declaration is given in the source file; see section :ref:`encodings`. .. index:: triple-quoted string, Unicode Consortium, raw string + single: """; string literal + single: '''; string literal In plain English: Both types of literals can be enclosed in matching single quotes (``'``) or double quotes (``"``). They can also be enclosed in matching groups @@ -442,11 +452,19 @@ of three single or double quotes (these are generally referred to as characters that otherwise have a special meaning, such as newline, backslash itself, or the quote character. +.. index:: + single: b'; bytes literal + single: b"; bytes literal + Bytes literals are always prefixed with ``'b'`` or ``'B'``; they produce an instance of the :class:`bytes` type instead of the :class:`str` type. They may only contain ASCII characters; bytes with a numeric value of 128 or greater must be expressed with escapes. +.. index:: + single: r'; raw string literal + single: r"; raw string literal + Both string and bytes literals may optionally be prefixed with a letter ``'r'`` or ``'R'``; such strings are called :dfn:`raw strings` and treat backslashes as literal characters. As a result, in string literals, ``'\U'`` and ``'\u'`` @@ -463,6 +481,10 @@ is not supported. to simplify the maintenance of dual Python 2.x and 3.x codebases. See :pep:`414` for more information. +.. index:: + single: f'; formatted string literal + single: f"; formatted string literal + A string literal with ``'f'`` or ``'F'`` in its prefix is a :dfn:`formatted string literal`; see :ref:`f-strings`. The ``'f'`` may be combined with ``'r'``, but not with ``'b'`` or ``'u'``, therefore raw @@ -473,6 +495,19 @@ retained), except that three unescaped quotes in a row terminate the literal. ( "quote" is the character used to open the literal, i.e. either ``'`` or ``"``.) .. index:: physical line, escape sequence, Standard C, C + single: \; escape sequence + single: \\; escape sequence + single: \a; escape sequence + single: \b; escape sequence + single: \f; escape sequence + single: \n; escape sequence + single: \r; escape sequence + single: \t; escape sequence + single: \v; escape sequence + single: \x; escape sequence + single: \N; escape sequence + single: \u; escape sequence + single: \U; escape sequence Unless an ``'r'`` or ``'R'`` prefix is present, escape sequences in string and bytes literals are interpreted according to rules similar to those used by @@ -604,6 +639,10 @@ and formatted string literals may be concatenated with plain string literals. single: string; formatted literal single: string; interpolated literal single: f-string + single: {; in formatted string literal + single: }; in formatted string literal + single: !; in formatted string literal + single: :; in formatted string literal .. _f-strings: Formatted string literals @@ -738,6 +777,12 @@ actually an expression composed of the unary operator '``-``' and the literal ``1``. +.. index:: + single: 0b; integer literal + single: 0o; integer literal + single: 0x; integer literal + single: _; in numeric literal + .. _integers: Integer literals @@ -778,6 +823,10 @@ Some examples of integer literals:: Underscores are now allowed for grouping purposes in literals. +.. index:: + single: .; in numeric literal + single: e; in numeric literal + single: _; in numeric literal .. _floating: Floating point literals @@ -806,6 +855,8 @@ Some examples of floating point literals:: Underscores are now allowed for grouping purposes in literals. +.. index:: + single: j; in numeric literal .. _imaginary: Imaginary literals |