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msgstr ""

"Project-Id-Version: Python 3.13\n"

"Report-Msgid-Bugs-To: \n"

"POT-Creation-Date: 2025-06-27 07:36+0000\n"

"PO-Revision-Date: 2018-05-23 16:17+0000\n"

"Last-Translator: Adrian Liaw <adrianliaw2000@gmail.com>\n"

"Language-Team: Chinese - TAIWAN (https://github.com/python/python-docs-zh-"

"tw)\n"

"Language: zh_TW\n"

"MIME-Version: 1.0\n"

"Content-Type: text/plain; charset=UTF-8\n"

"Content-Transfer-Encoding: 8bit\n"

"Plural-Forms: nplurals=1; plural=0;\n"

#: ../../reference/expressions.rst:6

msgid "Expressions"

msgstr "運算式"

#: ../../reference/expressions.rst:10

msgid ""

"This chapter explains the meaning of the elements of expressions in Python."

msgstr ""

#: ../../reference/expressions.rst:12

msgid ""

"**Syntax Notes:** In this and the following chapters, extended BNF notation "

"will be used to describe syntax, not lexical analysis. When (one "

"alternative of) a syntax rule has the form"

msgstr ""

#: ../../reference/expressions.rst:19

msgid ""

"and no semantics are given, the semantics of this form of ``name`` are the "

"same as for ``othername``."

msgstr ""

#: ../../reference/expressions.rst:26

msgid "Arithmetic conversions"

msgstr ""

#: ../../reference/expressions.rst:30

msgid ""

"When a description of an arithmetic operator below uses the phrase \"the "

"numeric arguments are converted to a common type\", this means that the "

"operator implementation for built-in types works as follows:"

msgstr ""

#: ../../reference/expressions.rst:34

msgid ""

"If either argument is a complex number, the other is converted to complex;"

msgstr ""

#: ../../reference/expressions.rst:36

msgid ""

"otherwise, if either argument is a floating-point number, the other is "

"converted to floating point;"

msgstr ""

#: ../../reference/expressions.rst:39

msgid "otherwise, both must be integers and no conversion is necessary."

msgstr ""

#: ../../reference/expressions.rst:41

msgid ""

"Some additional rules apply for certain operators (e.g., a string as a left "

"argument to the '%' operator). Extensions must define their own conversion "

"behavior."

msgstr ""

#: ../../reference/expressions.rst:49

msgid "Atoms"

msgstr ""

#: ../../reference/expressions.rst:53

msgid ""

"Atoms are the most basic elements of expressions. The simplest atoms are "

"identifiers or literals. Forms enclosed in parentheses, brackets or braces "

"are also categorized syntactically as atoms. The syntax for atoms is:"

msgstr ""

#: ../../reference/expressions.rst:66

msgid "Identifiers (Names)"

msgstr ""

#: ../../reference/expressions.rst:70

msgid ""

"An identifier occurring as an atom is a name. See section :ref:"

"`identifiers` for lexical definition and section :ref:`naming` for "

"documentation of naming and binding."

msgstr ""

#: ../../reference/expressions.rst:76

msgid ""

"When the name is bound to an object, evaluation of the atom yields that "

"object. When a name is not bound, an attempt to evaluate it raises a :exc:"

"`NameError` exception."

msgstr ""

#: ../../reference/expressions.rst:87

msgid "Private name mangling"

msgstr ""

#: ../../reference/expressions.rst:89

msgid ""

"When an identifier that textually occurs in a class definition begins with "

"two or more underscore characters and does not end in two or more "

"underscores, it is considered a :dfn:`private name` of that class."

msgstr ""

#: ../../reference/expressions.rst:95

msgid "The :ref:`class specifications <class>`."

msgstr ""

#: ../../reference/expressions.rst:97

msgid ""

"More precisely, private names are transformed to a longer form before code "

"is generated for them. If the transformed name is longer than 255 "

"characters, implementation-defined truncation may happen."

msgstr ""

#: ../../reference/expressions.rst:101

msgid ""

"The transformation is independent of the syntactical context in which the "

"identifier is used but only the following private identifiers are mangled:"

msgstr ""

#: ../../reference/expressions.rst:104

msgid ""

"Any name used as the name of a variable that is assigned or read or any name "

"of an attribute being accessed."

msgstr ""

#: ../../reference/expressions.rst:107

msgid ""

"The :attr:`~definition.__name__` attribute of nested functions, classes, and "

"type aliases is however not mangled."

msgstr ""

#: ../../reference/expressions.rst:110

msgid ""

"The name of imported modules, e.g., ``__spam`` in ``import __spam``. If the "

"module is part of a package (i.e., its name contains a dot), the name is "

"*not* mangled, e.g., the ``__foo`` in ``import __foo.bar`` is not mangled."

msgstr ""

#: ../../reference/expressions.rst:115

msgid ""

"The name of an imported member, e.g., ``__f`` in ``from spam import __f``."

msgstr ""

#: ../../reference/expressions.rst:117

msgid "The transformation rule is defined as follows:"

msgstr ""

#: ../../reference/expressions.rst:119

msgid ""

"The class name, with leading underscores removed and a single leading "

"underscore inserted, is inserted in front of the identifier, e.g., the "

"identifier ``__spam`` occurring in a class named ``Foo``, ``_Foo`` or "

"``__Foo`` is transformed to ``_Foo__spam``."

msgstr ""

#: ../../reference/expressions.rst:124

msgid ""

"If the class name consists only of underscores, the transformation is the "

"identity, e.g., the identifier ``__spam`` occurring in a class named ``_`` "

"or ``__`` is left as is."

msgstr ""

#: ../../reference/expressions.rst:131

msgid "Literals"

msgstr ""

#: ../../reference/expressions.rst:135

msgid "Python supports string and bytes literals and various numeric literals:"

msgstr ""

#: ../../reference/expressions.rst:141

msgid ""

"Evaluation of a literal yields an object of the given type (string, bytes, "

"integer, floating-point number, complex number) with the given value. The "

"value may be approximated in the case of floating-point and imaginary "

"(complex) literals. See section :ref:`literals` for details."

msgstr ""

#: ../../reference/expressions.rst:150

msgid ""

"All literals correspond to immutable data types, and hence the object's "

"identity is less important than its value. Multiple evaluations of literals "

"with the same value (either the same occurrence in the program text or a "

"different occurrence) may obtain the same object or a different object with "

"the same value."

msgstr ""

#: ../../reference/expressions.rst:160

msgid "Parenthesized forms"

msgstr ""

#: ../../reference/expressions.rst:166

msgid ""

"A parenthesized form is an optional expression list enclosed in parentheses:"

msgstr ""

#: ../../reference/expressions.rst:171

msgid ""

"A parenthesized expression list yields whatever that expression list yields: "

"if the list contains at least one comma, it yields a tuple; otherwise, it "

"yields the single expression that makes up the expression list."

msgstr ""

#: ../../reference/expressions.rst:177

msgid ""

"An empty pair of parentheses yields an empty tuple object. Since tuples are "

"immutable, the same rules as for literals apply (i.e., two occurrences of "

"the empty tuple may or may not yield the same object)."

msgstr ""

#: ../../reference/expressions.rst:185

msgid ""

"Note that tuples are not formed by the parentheses, but rather by use of the "

"comma. The exception is the empty tuple, for which parentheses *are* "

"required --- allowing unparenthesized \"nothing\" in expressions would cause "

"ambiguities and allow common typos to pass uncaught."

msgstr ""

#: ../../reference/expressions.rst:194

msgid "Displays for lists, sets and dictionaries"

msgstr ""

#: ../../reference/expressions.rst:198

msgid ""

"For constructing a list, a set or a dictionary Python provides special "

"syntax called \"displays\", each of them in two flavors:"

msgstr ""

#: ../../reference/expressions.rst:201

msgid "either the container contents are listed explicitly, or"

msgstr ""

#: ../../reference/expressions.rst:203

msgid ""

"they are computed via a set of looping and filtering instructions, called a :"

"dfn:`comprehension`."

msgstr ""

#: ../../reference/expressions.rst:211

msgid "Common syntax elements for comprehensions are:"

msgstr ""

#: ../../reference/expressions.rst:219

msgid ""

"The comprehension consists of a single expression followed by at least one :"

"keyword:`!for` clause and zero or more :keyword:`!for` or :keyword:`!if` "

"clauses. In this case, the elements of the new container are those that "

"would be produced by considering each of the :keyword:`!for` or :keyword:`!"

"if` clauses a block, nesting from left to right, and evaluating the "

"expression to produce an element each time the innermost block is reached."

msgstr ""

#: ../../reference/expressions.rst:226

msgid ""

"However, aside from the iterable expression in the leftmost :keyword:`!for` "

"clause, the comprehension is executed in a separate implicitly nested scope. "

"This ensures that names assigned to in the target list don't \"leak\" into "

"the enclosing scope."

msgstr ""

#: ../../reference/expressions.rst:230

msgid ""

"The iterable expression in the leftmost :keyword:`!for` clause is evaluated "

"directly in the enclosing scope and then passed as an argument to the "

"implicitly nested scope. Subsequent :keyword:`!for` clauses and any filter "

"condition in the leftmost :keyword:`!for` clause cannot be evaluated in the "

"enclosing scope as they may depend on the values obtained from the leftmost "

"iterable. For example: ``[x*y for x in range(10) for y in range(x, x+10)]``."

msgstr ""

#: ../../reference/expressions.rst:237

msgid ""

"To ensure the comprehension always results in a container of the appropriate "

"type, ``yield`` and ``yield from`` expressions are prohibited in the "

"implicitly nested scope."

msgstr ""

#: ../../reference/expressions.rst:244

msgid ""

"Since Python 3.6, in an :keyword:`async def` function, an :keyword:`!async "

"for` clause may be used to iterate over a :term:`asynchronous iterator`. A "

"comprehension in an :keyword:`!async def` function may consist of either a :"

"keyword:`!for` or :keyword:`!async for` clause following the leading "

"expression, may contain additional :keyword:`!for` or :keyword:`!async for` "

"clauses, and may also use :keyword:`await` expressions."

msgstr ""

#: ../../reference/expressions.rst:251

msgid ""

"If a comprehension contains :keyword:`!async for` clauses, or if it "

"contains :keyword:`!await` expressions or other asynchronous comprehensions "

"anywhere except the iterable expression in the leftmost :keyword:`!for` "

"clause, it is called an :dfn:`asynchronous comprehension`. An asynchronous "

"comprehension may suspend the execution of the coroutine function in which "

"it appears. See also :pep:`530`."

msgstr ""

#: ../../reference/expressions.rst:258

msgid "Asynchronous comprehensions were introduced."

msgstr ""

#: ../../reference/expressions.rst:261 ../../reference/expressions.rst:440

msgid "``yield`` and ``yield from`` prohibited in the implicitly nested scope."

msgstr ""

#: ../../reference/expressions.rst:264

msgid ""

"Asynchronous comprehensions are now allowed inside comprehensions in "

"asynchronous functions. Outer comprehensions implicitly become asynchronous."

msgstr ""

#: ../../reference/expressions.rst:273

msgid "List displays"

msgstr ""

#: ../../reference/expressions.rst:283

msgid ""

"A list display is a possibly empty series of expressions enclosed in square "

"brackets:"

msgstr ""

#: ../../reference/expressions.rst:289

msgid ""

"A list display yields a new list object, the contents being specified by "

"either a list of expressions or a comprehension. When a comma-separated "

"list of expressions is supplied, its elements are evaluated from left to "

"right and placed into the list object in that order. When a comprehension "

"is supplied, the list is constructed from the elements resulting from the "

"comprehension."

msgstr ""

#: ../../reference/expressions.rst:299

msgid "Set displays"

msgstr ""

#: ../../reference/expressions.rst:308

msgid ""

"A set display is denoted by curly braces and distinguishable from dictionary "

"displays by the lack of colons separating keys and values:"

msgstr ""

#: ../../reference/expressions.rst:314

msgid ""

"A set display yields a new mutable set object, the contents being specified "

"by either a sequence of expressions or a comprehension. When a comma-"

"separated list of expressions is supplied, its elements are evaluated from "

"left to right and added to the set object. When a comprehension is "

"supplied, the set is constructed from the elements resulting from the "

"comprehension."

msgstr ""

#: ../../reference/expressions.rst:320

msgid ""

"An empty set cannot be constructed with ``{}``; this literal constructs an "

"empty dictionary."

msgstr ""

#: ../../reference/expressions.rst:327

msgid "Dictionary displays"

msgstr ""

#: ../../reference/expressions.rst:338

msgid ""

"A dictionary display is a possibly empty series of dict items (key/value "

"pairs) enclosed in curly braces:"

msgstr ""

#: ../../reference/expressions.rst:347

msgid "A dictionary display yields a new dictionary object."

msgstr ""

#: ../../reference/expressions.rst:349

msgid ""

"If a comma-separated sequence of dict items is given, they are evaluated "

"from left to right to define the entries of the dictionary: each key object "

"is used as a key into the dictionary to store the corresponding value. This "

"means that you can specify the same key multiple times in the dict item "

"list, and the final dictionary's value for that key will be the last one "

"given."

msgstr ""

#: ../../reference/expressions.rst:359

msgid ""

"A double asterisk ``**`` denotes :dfn:`dictionary unpacking`. Its operand "

"must be a :term:`mapping`. Each mapping item is added to the new "

"dictionary. Later values replace values already set by earlier dict items "

"and earlier dictionary unpackings."

msgstr ""

#: ../../reference/expressions.rst:364

msgid "Unpacking into dictionary displays, originally proposed by :pep:`448`."

msgstr ""

#: ../../reference/expressions.rst:367

msgid ""

"A dict comprehension, in contrast to list and set comprehensions, needs two "

"expressions separated with a colon followed by the usual \"for\" and \"if\" "

"clauses. When the comprehension is run, the resulting key and value elements "

"are inserted in the new dictionary in the order they are produced."

msgstr ""

#: ../../reference/expressions.rst:375

msgid ""

"Restrictions on the types of the key values are listed earlier in section :"

"ref:`types`. (To summarize, the key type should be :term:`hashable`, which "

"excludes all mutable objects.) Clashes between duplicate keys are not "

"detected; the last value (textually rightmost in the display) stored for a "

"given key value prevails."

msgstr ""

#: ../../reference/expressions.rst:381

msgid ""

"Prior to Python 3.8, in dict comprehensions, the evaluation order of key and "

"value was not well-defined. In CPython, the value was evaluated before the "

"key. Starting with 3.8, the key is evaluated before the value, as proposed "

"by :pep:`572`."

msgstr ""

#: ../../reference/expressions.rst:391

msgid "Generator expressions"

msgstr ""

#: ../../reference/expressions.rst:398

msgid "A generator expression is a compact generator notation in parentheses:"

msgstr ""

#: ../../reference/expressions.rst:403

msgid ""

"A generator expression yields a new generator object. Its syntax is the "

"same as for comprehensions, except that it is enclosed in parentheses "

"instead of brackets or curly braces."

msgstr ""

#: ../../reference/expressions.rst:407

msgid ""

"Variables used in the generator expression are evaluated lazily when the :"

"meth:`~generator.__next__` method is called for the generator object (in the "

"same fashion as normal generators). However, the iterable expression in the "

"leftmost :keyword:`!for` clause is immediately evaluated, and the :term:"

"`iterator` is immediately created for that iterable, so that an error "

"produced while creating the iterator will be emitted at the point where the "

"generator expression is defined, rather than at the point where the first "

"value is retrieved. Subsequent :keyword:`!for` clauses and any filter "

"condition in the leftmost :keyword:`!for` clause cannot be evaluated in the "

"enclosing scope as they may depend on the values obtained from the leftmost "

"iterable. For example: ``(x*y for x in range(10) for y in range(x, x+10))``."

msgstr ""

#: ../../reference/expressions.rst:419

msgid ""

"The parentheses can be omitted on calls with only one argument. See "

"section :ref:`calls` for details."

msgstr ""

#: ../../reference/expressions.rst:422

msgid ""

"To avoid interfering with the expected operation of the generator expression "

"itself, ``yield`` and ``yield from`` expressions are prohibited in the "

"implicitly defined generator."

msgstr ""

#: ../../reference/expressions.rst:426

msgid ""

"If a generator expression contains either :keyword:`!async for` clauses or :"

"keyword:`await` expressions it is called an :dfn:`asynchronous generator "

"expression`. An asynchronous generator expression returns a new "

"asynchronous generator object, which is an asynchronous iterator (see :ref:"

"`async-iterators`)."

msgstr ""

#: ../../reference/expressions.rst:432

msgid "Asynchronous generator expressions were introduced."

msgstr ""

#: ../../reference/expressions.rst:435

msgid ""

"Prior to Python 3.7, asynchronous generator expressions could only appear "

"in :keyword:`async def` coroutines. Starting with 3.7, any function can use "

"asynchronous generator expressions."

msgstr ""

#: ../../reference/expressions.rst:447

msgid "Yield expressions"

msgstr ""

#: ../../reference/expressions.rst:460

msgid ""

"The yield expression is used when defining a :term:`generator` function or "

"an :term:`asynchronous generator` function and thus can only be used in the "

"body of a function definition. Using a yield expression in a function's "

"body causes that function to be a generator function, and using it in an :"

"keyword:`async def` function's body causes that coroutine function to be an "

"asynchronous generator function. For example::"

msgstr ""

#: ../../reference/expressions.rst:467

msgid ""

"def gen(): # defines a generator function\n"

" yield 123\n"

"\n"

"async def agen(): # defines an asynchronous generator function\n"

" yield 123"

msgstr ""

#: ../../reference/expressions.rst:473

msgid ""

"Due to their side effects on the containing scope, ``yield`` expressions are "

"not permitted as part of the implicitly defined scopes used to implement "

"comprehensions and generator expressions."

msgstr ""

#: ../../reference/expressions.rst:477

msgid ""

"Yield expressions prohibited in the implicitly nested scopes used to "

"implement comprehensions and generator expressions."

msgstr ""

#: ../../reference/expressions.rst:481

msgid ""

"Generator functions are described below, while asynchronous generator "

"functions are described separately in section :ref:`asynchronous-generator-"

"functions`."

msgstr ""

#: ../../reference/expressions.rst:485

msgid ""

"When a generator function is called, it returns an iterator known as a "

"generator. That generator then controls the execution of the generator "

"function. The execution starts when one of the generator's methods is "

"called. At that time, the execution proceeds to the first yield expression, "

"where it is suspended again, returning the value of :token:`~python-grammar:"

"yield_list` to the generator's caller, or ``None`` if :token:`~python-"

"grammar:yield_list` is omitted. By suspended, we mean that all local state "

"is retained, including the current bindings of local variables, the "

"instruction pointer, the internal evaluation stack, and the state of any "

"exception handling. When the execution is resumed by calling one of the "

"generator's methods, the function can proceed exactly as if the yield "

"expression were just another external call. The value of the yield "

"expression after resuming depends on the method which resumed the "

"execution. If :meth:`~generator.__next__` is used (typically via either a :"

"keyword:`for` or the :func:`next` builtin) then the result is :const:"

"`None`. Otherwise, if :meth:`~generator.send` is used, then the result will "

"be the value passed in to that method."

msgstr ""

#: ../../reference/expressions.rst:505

msgid ""

"All of this makes generator functions quite similar to coroutines; they "

"yield multiple times, they have more than one entry point and their "

"execution can be suspended. The only difference is that a generator "

"function cannot control where the execution should continue after it yields; "

"the control is always transferred to the generator's caller."

msgstr ""

#: ../../reference/expressions.rst:511

msgid ""

"Yield expressions are allowed anywhere in a :keyword:`try` construct. If "

"the generator is not resumed before it is finalized (by reaching a zero "

"reference count or by being garbage collected), the generator-iterator's :"

"meth:`~generator.close` method will be called, allowing any pending :keyword:"

"`finally` clauses to execute."

msgstr ""

#: ../../reference/expressions.rst:520

msgid ""

"When ``yield from <expr>`` is used, the supplied expression must be an "

"iterable. The values produced by iterating that iterable are passed directly "

"to the caller of the current generator's methods. Any values passed in with :"

"meth:`~generator.send` and any exceptions passed in with :meth:`~generator."

"throw` are passed to the underlying iterator if it has the appropriate "

"methods. If this is not the case, then :meth:`~generator.send` will raise :"

"exc:`AttributeError` or :exc:`TypeError`, while :meth:`~generator.throw` "

"will just raise the passed in exception immediately."

msgstr ""

#: ../../reference/expressions.rst:529

msgid ""

"When the underlying iterator is complete, the :attr:`~StopIteration.value` "

"attribute of the raised :exc:`StopIteration` instance becomes the value of "

"the yield expression. It can be either set explicitly when raising :exc:"

"`StopIteration`, or automatically when the subiterator is a generator (by "

"returning a value from the subgenerator)."

msgstr ""

#: ../../reference/expressions.rst:535

msgid "Added ``yield from <expr>`` to delegate control flow to a subiterator."

msgstr ""

#: ../../reference/expressions.rst:538

msgid ""

"The parentheses may be omitted when the yield expression is the sole "

"expression on the right hand side of an assignment statement."

msgstr ""

#: ../../reference/expressions.rst:543

msgid ":pep:`255` - Simple Generators"

msgstr ""

#: ../../reference/expressions.rst:544

msgid ""

"The proposal for adding generators and the :keyword:`yield` statement to "

"Python."

msgstr ""

#: ../../reference/expressions.rst:546

msgid ":pep:`342` - Coroutines via Enhanced Generators"

msgstr ""

#: ../../reference/expressions.rst:547

msgid ""

"The proposal to enhance the API and syntax of generators, making them usable "

"as simple coroutines."

msgstr ""

#: ../../reference/expressions.rst:550

msgid ":pep:`380` - Syntax for Delegating to a Subgenerator"

msgstr ""

#: ../../reference/expressions.rst:551

msgid ""

"The proposal to introduce the :token:`~python-grammar:yield_from` syntax, "

"making delegation to subgenerators easy."

msgstr ""

#: ../../reference/expressions.rst:554

msgid ":pep:`525` - Asynchronous Generators"

msgstr ""

#: ../../reference/expressions.rst:555

msgid ""

"The proposal that expanded on :pep:`492` by adding generator capabilities to "

"coroutine functions."

msgstr ""

#: ../../reference/expressions.rst:562

msgid "Generator-iterator methods"

msgstr ""

#: ../../reference/expressions.rst:564

msgid ""

"This subsection describes the methods of a generator iterator. They can be "

"used to control the execution of a generator function."

msgstr ""

#: ../../reference/expressions.rst:567

msgid ""

"Note that calling any of the generator methods below when the generator is "

"already executing raises a :exc:`ValueError` exception."

msgstr ""

#: ../../reference/expressions.rst:575

msgid ""

"Starts the execution of a generator function or resumes it at the last "

"executed yield expression. When a generator function is resumed with a :"

"meth:`~generator.__next__` method, the current yield expression always "

"evaluates to :const:`None`. The execution then continues to the next yield "

"expression, where the generator is suspended again, and the value of the :"

"token:`~python-grammar:yield_list` is returned to :meth:`__next__`'s "

"caller. If the generator exits without yielding another value, a :exc:"

"`StopIteration` exception is raised."

msgstr ""

#: ../../reference/expressions.rst:584

msgid ""

"This method is normally called implicitly, e.g. by a :keyword:`for` loop, or "

"by the built-in :func:`next` function."

msgstr ""

#: ../../reference/expressions.rst:590

msgid ""

"Resumes the execution and \"sends\" a value into the generator function. "

"The *value* argument becomes the result of the current yield expression. "

"The :meth:`send` method returns the next value yielded by the generator, or "

"raises :exc:`StopIteration` if the generator exits without yielding another "

"value. When :meth:`send` is called to start the generator, it must be "

"called with :const:`None` as the argument, because there is no yield "

"expression that could receive the value."

msgstr ""

#: ../../reference/expressions.rst:602

msgid ""

"Raises an exception at the point where the generator was paused, and returns "

"the next value yielded by the generator function. If the generator exits "

"without yielding another value, a :exc:`StopIteration` exception is raised. "

"If the generator function does not catch the passed-in exception, or raises "

"a different exception, then that exception propagates to the caller."

msgstr ""

#: ../../reference/expressions.rst:608

msgid ""

"In typical use, this is called with a single exception instance similar to "

"the way the :keyword:`raise` keyword is used."

msgstr ""

#: ../../reference/expressions.rst:611

msgid ""

"For backwards compatibility, however, the second signature is supported, "

"following a convention from older versions of Python. The *type* argument "

"should be an exception class, and *value* should be an exception instance. "

"If the *value* is not provided, the *type* constructor is called to get an "

"instance. If *traceback* is provided, it is set on the exception, otherwise "

"any existing :attr:`~BaseException.__traceback__` attribute stored in "

"*value* may be cleared."

msgstr ""

#: ../../reference/expressions.rst:622 ../../reference/expressions.rst:808

msgid ""

"The second signature \\(type\\[, value\\[, traceback\\]\\]\\) is deprecated "

"and may be removed in a future version of Python."

msgstr ""

#: ../../reference/expressions.rst:630

msgid ""

"Raises a :exc:`GeneratorExit` exception at the point where the generator "

"function was paused (equivalent to calling ``throw(GeneratorExit)``). The "

"exception is raised by the yield expression where the generator was paused. "

"If the generator function catches the exception and returns a value, this "

"value is returned from :meth:`close`. If the generator function is already "

"closed, or raises :exc:`GeneratorExit` (by not catching the exception), :"

"meth:`close` returns :const:`None`. If the generator yields a value, a :exc:"

"`RuntimeError` is raised. If the generator raises any other exception, it "

"is propagated to the caller. If the generator has already exited due to an "

"exception or normal exit, :meth:`close` returns :const:`None` and has no "

"other effect."

msgstr ""

#: ../../reference/expressions.rst:644

msgid ""

"If a generator returns a value upon being closed, the value is returned by :"

"meth:`close`."

msgstr ""

#: ../../reference/expressions.rst:650

msgid "Examples"

msgstr "模組"

#: ../../reference/expressions.rst:652

msgid ""

"Here is a simple example that demonstrates the behavior of generators and "

"generator functions::"

msgstr ""

#: ../../reference/expressions.rst:655

msgid ""

">>> def echo(value=None):\n"

"... print(\"Execution starts when 'next()' is called for the first time."

"\")\n"

"... try:\n"

"... while True:\n"

"... try:\n"

"... value = (yield value)\n"

"... except Exception as e:\n"

"... value = e\n"

"... finally:\n"

"... print(\"Don't forget to clean up when 'close()' is called.\")\n"

"...\n"

">>> generator = echo(1)\n"

">>> print(next(generator))\n"

"Execution starts when 'next()' is called for the first time.\n"

"1\n"

">>> print(next(generator))\n"

"None\n"

">>> print(generator.send(2))\n"

"2\n"

">>> generator.throw(TypeError, \"spam\")\n"

"TypeError('spam',)\n"

">>> generator.close()\n"

"Don't forget to clean up when 'close()' is called."

msgstr ""

#: ../../reference/expressions.rst:679

msgid ""

"For examples using ``yield from``, see :ref:`pep-380` in \"What's New in "

"Python.\""

msgstr ""

#: ../../reference/expressions.rst:685

msgid "Asynchronous generator functions"

msgstr "非同步產生器函式"

#: ../../reference/expressions.rst:687

msgid ""

"The presence of a yield expression in a function or method defined using :"

"keyword:`async def` further defines the function as an :term:`asynchronous "

"generator` function."

msgstr ""

#: ../../reference/expressions.rst:691

msgid ""

"When an asynchronous generator function is called, it returns an "

"asynchronous iterator known as an asynchronous generator object. That object "

"then controls the execution of the generator function. An asynchronous "

"generator object is typically used in an :keyword:`async for` statement in a "

"coroutine function analogously to how a generator object would be used in a :"

"keyword:`for` statement."

msgstr ""

#: ../../reference/expressions.rst:698

msgid ""

"Calling one of the asynchronous generator's methods returns an :term:"

"`awaitable` object, and the execution starts when this object is awaited on. "

"At that time, the execution proceeds to the first yield expression, where it "

"is suspended again, returning the value of :token:`~python-grammar:"

"yield_list` to the awaiting coroutine. As with a generator, suspension means "

"that all local state is retained, including the current bindings of local "

"variables, the instruction pointer, the internal evaluation stack, and the "

"state of any exception handling. When the execution is resumed by awaiting "

"on the next object returned by the asynchronous generator's methods, the "

"function can proceed exactly as if the yield expression were just another "

"external call. The value of the yield expression after resuming depends on "

"the method which resumed the execution. If :meth:`~agen.__anext__` is used "

"then the result is :const:`None`. Otherwise, if :meth:`~agen.asend` is used, "

"then the result will be the value passed in to that method."

msgstr ""

#: ../../reference/expressions.rst:713

msgid ""

"If an asynchronous generator happens to exit early by :keyword:`break`, the "

"caller task being cancelled, or other exceptions, the generator's async "

"cleanup code will run and possibly raise exceptions or access context "

"variables in an unexpected context--perhaps after the lifetime of tasks it "

"depends, or during the event loop shutdown when the async-generator garbage "

"collection hook is called. To prevent this, the caller must explicitly close "

"the async generator by calling :meth:`~agen.aclose` method to finalize the "

"generator and ultimately detach it from the event loop."

msgstr ""

#: ../../reference/expressions.rst:723

msgid ""

"In an asynchronous generator function, yield expressions are allowed "

"anywhere in a :keyword:`try` construct. However, if an asynchronous "

"generator is not resumed before it is finalized (by reaching a zero "

"reference count or by being garbage collected), then a yield expression "

"within a :keyword:`!try` construct could result in a failure to execute "

"pending :keyword:`finally` clauses. In this case, it is the responsibility "

"of the event loop or scheduler running the asynchronous generator to call "

"the asynchronous generator-iterator's :meth:`~agen.aclose` method and run "

"the resulting coroutine object, thus allowing any pending :keyword:`!"

"finally` clauses to execute."

msgstr ""

#: ../../reference/expressions.rst:734

msgid ""

"To take care of finalization upon event loop termination, an event loop "

"should define a *finalizer* function which takes an asynchronous generator-"

"iterator and presumably calls :meth:`~agen.aclose` and executes the "

"coroutine. This *finalizer* may be registered by calling :func:`sys."

"set_asyncgen_hooks`. When first iterated over, an asynchronous generator-"

"iterator will store the registered *finalizer* to be called upon "

"finalization. For a reference example of a *finalizer* method see the "

"implementation of ``asyncio.Loop.shutdown_asyncgens`` in :source:`Lib/"

"asyncio/base_events.py`."

msgstr ""

#: ../../reference/expressions.rst:743

msgid ""

"The expression ``yield from <expr>`` is a syntax error when used in an "

"asynchronous generator function."

msgstr ""

#: ../../reference/expressions.rst:750

msgid "Asynchronous generator-iterator methods"

msgstr ""

#: ../../reference/expressions.rst:752

msgid ""

"This subsection describes the methods of an asynchronous generator iterator, "

"which are used to control the execution of a generator function."

msgstr ""

#: ../../reference/expressions.rst:761

msgid ""

"Returns an awaitable which when run starts to execute the asynchronous "

"generator or resumes it at the last executed yield expression. When an "

"asynchronous generator function is resumed with an :meth:`~agen.__anext__` "

"method, the current yield expression always evaluates to :const:`None` in "

"the returned awaitable, which when run will continue to the next yield "

"expression. The value of the :token:`~python-grammar:yield_list` of the "

"yield expression is the value of the :exc:`StopIteration` exception raised "

"by the completing coroutine. If the asynchronous generator exits without "

"yielding another value, the awaitable instead raises a :exc:"

"`StopAsyncIteration` exception, signalling that the asynchronous iteration "

"has completed."

msgstr ""

#: ../../reference/expressions.rst:773

msgid ""

"This method is normally called implicitly by a :keyword:`async for` loop."

msgstr ""

#: ../../reference/expressions.rst:779

msgid ""

"Returns an awaitable which when run resumes the execution of the "

"asynchronous generator. As with the :meth:`~generator.send` method for a "

"generator, this \"sends\" a value into the asynchronous generator function, "

"and the *value* argument becomes the result of the current yield expression. "

"The awaitable returned by the :meth:`asend` method will return the next "

"value yielded by the generator as the value of the raised :exc:"

"`StopIteration`, or raises :exc:`StopAsyncIteration` if the asynchronous "

"generator exits without yielding another value. When :meth:`asend` is "

"called to start the asynchronous generator, it must be called with :const:"

"`None` as the argument, because there is no yield expression that could "

"receive the value."

msgstr ""

#: ../../reference/expressions.rst:796

msgid ""

"Returns an awaitable that raises an exception of type ``type`` at the point "

"where the asynchronous generator was paused, and returns the next value "

"yielded by the generator function as the value of the raised :exc:"

"`StopIteration` exception. If the asynchronous generator exits without "

"yielding another value, a :exc:`StopAsyncIteration` exception is raised by "

"the awaitable. If the generator function does not catch the passed-in "

"exception, or raises a different exception, then when the awaitable is run "

"that exception propagates to the caller of the awaitable."

msgstr ""

#: ../../reference/expressions.rst:817

msgid ""

"Returns an awaitable that when run will throw a :exc:`GeneratorExit` into "

"the asynchronous generator function at the point where it was paused. If the "

"asynchronous generator function then exits gracefully, is already closed, or "

"raises :exc:`GeneratorExit` (by not catching the exception), then the "

"returned awaitable will raise a :exc:`StopIteration` exception. Any further "

"awaitables returned by subsequent calls to the asynchronous generator will "

"raise a :exc:`StopAsyncIteration` exception. If the asynchronous generator "

"yields a value, a :exc:`RuntimeError` is raised by the awaitable. If the "

"asynchronous generator raises any other exception, it is propagated to the "

"caller of the awaitable. If the asynchronous generator has already exited "

"due to an exception or normal exit, then further calls to :meth:`aclose` "

"will return an awaitable that does nothing."

msgstr ""

#: ../../reference/expressions.rst:833

msgid "Primaries"

msgstr ""

#: ../../reference/expressions.rst:837

msgid ""

"Primaries represent the most tightly bound operations of the language. Their "

"syntax is:"

msgstr ""

#: ../../reference/expressions.rst:847

msgid "Attribute references"

msgstr ""

#: ../../reference/expressions.rst:853

msgid "An attribute reference is a primary followed by a period and a name:"

msgstr ""

#: ../../reference/expressions.rst:863

msgid ""

"The primary must evaluate to an object of a type that supports attribute "

"references, which most objects do. This object is then asked to produce the "

"attribute whose name is the identifier. The type and value produced is "

"determined by the object. Multiple evaluations of the same attribute "

"reference may yield different objects."

msgstr ""

#: ../../reference/expressions.rst:869

msgid ""

"This production can be customized by overriding the :meth:`~object."

"__getattribute__` method or the :meth:`~object.__getattr__` method. The :"

"meth:`!__getattribute__` method is called first and either returns a value "

"or raises :exc:`AttributeError` if the attribute is not available."

msgstr ""

#: ../../reference/expressions.rst:875

msgid ""

"If an :exc:`AttributeError` is raised and the object has a :meth:`!"

"__getattr__` method, that method is called as a fallback."

msgstr ""

#: ../../reference/expressions.rst:881

msgid "Subscriptions"

msgstr ""

#: ../../reference/expressions.rst:896

msgid ""

"The subscription of an instance of a :ref:`container class <sequence-types>` "

"will generally select an element from the container. The subscription of a :"

"term:`generic class <generic type>` will generally return a :ref:"

"`GenericAlias <types-genericalias>` object."

msgstr ""

#: ../../reference/expressions.rst:904