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# Translators:

# python-doc bot, 2025

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# 99 <wh2099@pm.me>, 2026

# Freesand Leo <yuqinju@163.com>, 2026

#

#, fuzzy

msgid ""

msgstr ""

"Project-Id-Version: Python 3.14\n"

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

"POT-Creation-Date: 2026-02-19 14:43+0000\n"

"PO-Revision-Date: 2025-09-16 00:02+0000\n"

"Last-Translator: Freesand Leo <yuqinju@163.com>, 2026\n"

"Language-Team: Chinese (China) (https://app.transifex.com/python-doc/teams/5390/zh_CN/)\n"

"MIME-Version: 1.0\n"

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

"Language: zh_CN\n"

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

#: ../../tutorial/controlflow.rst:5

msgid "More Control Flow Tools"

msgstr "更多控制流工具"

#: ../../tutorial/controlflow.rst:7

msgid ""

"As well as the :keyword:`while` statement just introduced, Python uses a few"

" more that we will encounter in this chapter."

msgstr "除了刚介绍的 :keyword:`while` 语句，Python 还用了一些别的。我们将在本章中遇到它们。"

#: ../../tutorial/controlflow.rst:14

msgid ":keyword:`!if` Statements"

msgstr ":keyword:`!if` 语句"

#: ../../tutorial/controlflow.rst:16

msgid ""

"Perhaps the most well-known statement type is the :keyword:`if` statement. "

"For example::"

msgstr "最让人耳熟能详的语句应当是 :keyword:`if` 语句："

#: ../../tutorial/controlflow.rst:19

msgid ""

">>> x = int(input(\"Please enter an integer: \"))\n"

"Please enter an integer: 42\n"

">>> if x < 0:\n"

"... x = 0\n"

"... print('Negative changed to zero')\n"

"... elif x == 0:\n"

"... print('Zero')\n"

"... elif x == 1:\n"

"... print('Single')\n"

"... else:\n"

"... print('More')\n"

"...\n"

"More"

msgstr ""

">>> x = int(input(\"Please enter an integer: \"))\n"

"Please enter an integer: 42\n"

">>> if x < 0:\n"

"... x = 0\n"

"... print('Negative changed to zero')\n"

"... elif x == 0:\n"

"... print('Zero')\n"

"... elif x == 1:\n"

"... print('Single')\n"

"... else:\n"

"... print('More')\n"

"...\n"

"More"

#: ../../tutorial/controlflow.rst:33

msgid ""

"There can be zero or more :keyword:`elif` parts, and the :keyword:`else` "

"part is optional. The keyword ':keyword:`!elif`' is short for 'else if', "

"and is useful to avoid excessive indentation. An :keyword:`!if` ... "

":keyword:`!elif` ... :keyword:`!elif` ... sequence is a substitute for the "

"``switch`` or ``case`` statements found in other languages."

msgstr ""

"可有零个或多个 :keyword:`elif` 部分，:keyword:`else` 部分也是可选的。关键字 ':keyword:`!elif`' 是 "

"'else if' 的缩写，用于避免过多的缩进。:keyword:`!if` ... :keyword:`!elif` ... "

":keyword:`!elif` ... 序列可以当作其它语言中 ``switch`` 或 ``case`` 语句的替代品。"

#: ../../tutorial/controlflow.rst:39

msgid ""

"If you're comparing the same value to several constants, or checking for "

"specific types or attributes, you may also find the :keyword:`!match` "

"statement useful. For more details see :ref:`tut-match`."

msgstr ""

"如果是把一个值与多个常量进行比较，或者检查特定类型或属性，:keyword:`!match` 语句更有用。详见 :ref:`tut-match`。"

#: ../../tutorial/controlflow.rst:46

msgid ":keyword:`!for` Statements"

msgstr ":keyword:`!for` 语句"

#: ../../tutorial/controlflow.rst:51

msgid ""

"The :keyword:`for` statement in Python differs a bit from what you may be "

"used to in C or Pascal. Rather than always iterating over an arithmetic "

"progression of numbers (like in Pascal), or giving the user the ability to "

"define both the iteration step and halting condition (as C), Python's "

":keyword:`!for` statement iterates over the items of any sequence (a list or"

" a string), in the order that they appear in the sequence. For example (no "

"pun intended):"

msgstr ""

"Python 的 :keyword:`for` 语句与 C 或 Pascal 中的不同。Python 的 :keyword:`!for` "

"语句不迭代算术递增数值（如 Pascal），或是给予用户定义迭代步骤和结束条件的能力（如 "

"C），而是在列表或字符串等任意序列的元素上迭代，按它们在序列中出现的顺序。 例如（这不是有意要暗指什么）："

#: ../../tutorial/controlflow.rst:63

msgid ""

">>> # Measure some strings:\n"

">>> words = ['cat', 'window', 'defenestrate']\n"

">>> for w in words:\n"

"... print(w, len(w))\n"

"...\n"

"cat 3\n"

"window 6\n"

"defenestrate 12"

msgstr ""

">>> # 度量一些字符串：\n"

">>> words = ['cat', 'window', 'defenestrate']\n"

">>> for w in words:\n"

"... print(w, len(w))\n"

"...\n"

"cat 3\n"

"window 6\n"

"defenestrate 12"

#: ../../tutorial/controlflow.rst:72

msgid ""

"Code that modifies a collection while iterating over that same collection "

"can be tricky to get right. Instead, it is usually more straight-forward to"

" loop over a copy of the collection or to create a new collection::"

msgstr "很难正确地在迭代多项集的同时修改多项集的内容。更简单的方法是迭代多项集的副本或者创建新的多项集："

#: ../../tutorial/controlflow.rst:76

msgid ""

"# Create a sample collection\n"

"users = {'Hans': 'active', 'Éléonore': 'inactive', '景太郎': 'active'}\n"

"\n"

"# Strategy: Iterate over a copy\n"

"for user, status in users.copy().items():\n"

" if status == 'inactive':\n"

" del users[user]\n"

"\n"

"# Strategy: Create a new collection\n"

"active_users = {}\n"

"for user, status in users.items():\n"

" if status == 'active':\n"

" active_users[user] = status"

msgstr ""

"# 创建示例多项集\n"

"users = {'Hans': 'active', 'Éléonore': 'inactive', '景太郎': 'active'}\n"

"\n"

"# 策略：迭代一个副本\n"

"for user, status in users.copy().items():\n"

" if status == 'inactive':\n"

" del users[user]\n"

"\n"

"# 策略：创建一个新多项集\n"

"active_users = {}\n"

"for user, status in users.items():\n"

" if status == 'active':\n"

" active_users[user] = status"

#: ../../tutorial/controlflow.rst:94

msgid "The :func:`range` Function"

msgstr ":func:`range` 函数"

#: ../../tutorial/controlflow.rst:96

msgid ""

"If you do need to iterate over a sequence of numbers, the built-in function "

":func:`range` comes in handy. It generates arithmetic progressions::"

msgstr "内置函数 :func:`range` 用于生成等差数列："

#: ../../tutorial/controlflow.rst:99

msgid ""

">>> for i in range(5):\n"

"... print(i)\n"

"...\n"

"0\n"

"1\n"

"2\n"

"3\n"

"4"

msgstr ""

">>> for i in range(5):\n"

"... print(i)\n"

"...\n"

"0\n"

"1\n"

"2\n"

"3\n"

"4"

#: ../../tutorial/controlflow.rst:108

msgid ""

"The given end point is never part of the generated sequence; ``range(10)`` "

"generates 10 values, the legal indices for items of a sequence of length 10."

" It is possible to let the range start at another number, or to specify a "

"different increment (even negative; sometimes this is called the 'step')::"

msgstr ""

"生成的序列绝不会包括给定的终止值；``range(10)`` 生成 10 个值——长度为 10 的序列的所有合法索引。range 可以不从 0 "

"开始，且可以按给定的步长递增（即使是负数步长）："

#: ../../tutorial/controlflow.rst:113

msgid ""

">>> list(range(5, 10))\n"

"[5, 6, 7, 8, 9]\n"

"\n"

">>> list(range(0, 10, 3))\n"

"[0, 3, 6, 9]\n"

"\n"

">>> list(range(-10, -100, -30))\n"

"[-10, -40, -70]"

msgstr ""

">>> list(range(5, 10))\n"

"[5, 6, 7, 8, 9]\n"

"\n"

">>> list(range(0, 10, 3))\n"

"[0, 3, 6, 9]\n"

"\n"

">>> list(range(-10, -100, -30))\n"

"[-10, -40, -70]"

#: ../../tutorial/controlflow.rst:122

msgid ""

"To iterate over the indices of a sequence, you can combine :func:`range` and"

" :func:`len` as follows::"

msgstr "要按索引迭代序列，可以组合使用 :func:`range` 和 :func:`len`："

#: ../../tutorial/controlflow.rst:125

msgid ""

">>> a = ['Mary', 'had', 'a', 'little', 'lamb']\n"

">>> for i in range(len(a)):\n"

"... print(i, a[i])\n"

"...\n"

"0 Mary\n"

"1 had\n"

"2 a\n"

"3 little\n"

"4 lamb"

msgstr ""

">>> a = ['Mary', 'had', 'a', 'little', 'lamb']\n"

">>> for i in range(len(a)):\n"

"... print(i, a[i])\n"

"...\n"

"0 Mary\n"

"1 had\n"

"2 a\n"

"3 little\n"

"4 lamb"

#: ../../tutorial/controlflow.rst:135

msgid ""

"In most such cases, however, it is convenient to use the :func:`enumerate` "

"function, see :ref:`tut-loopidioms`."

msgstr "不过大多数情况下 :func:`enumerate` 函数很方便，详见 :ref:`tut-loopidioms`。"

#: ../../tutorial/controlflow.rst:138

msgid "A strange thing happens if you just print a range::"

msgstr "如果直接打印一个 range 会发生意想不到的事情："

#: ../../tutorial/controlflow.rst:140

msgid ""

">>> range(10)\n"

"range(0, 10)"

msgstr ""

">>> range(10)\n"

"range(0, 10)"

#: ../../tutorial/controlflow.rst:143

msgid ""

"In many ways the object returned by :func:`range` behaves as if it is a "

"list, but in fact it isn't. It is an object which returns the successive "

"items of the desired sequence when you iterate over it, but it doesn't "

"really make the list, thus saving space."

msgstr ""

":func:`range` "

"返回的对象在很多方面和列表的行为一样，但其实它和列表不一样。该对象只有在被迭代时才一个一个地返回所期望的列表项，并没有真正生成过一个含有全部项的列表，从而节省了空间。"

#: ../../tutorial/controlflow.rst:148

msgid ""

"We say such an object is :term:`iterable`, that is, suitable as a target for"

" functions and constructs that expect something from which they can obtain "

"successive items until the supply is exhausted. We have seen that the "

":keyword:`for` statement is such a construct, while an example of a function"

" that takes an iterable is :func:`sum`::"

msgstr ""

"这种对象称为可迭代对象 :term:`iterable`，适合作为需要获取一系列值的函数或程序构件的参数。:keyword:`for` "

"语句就是这样的程序构件；以可迭代对象作为参数的函数例如 :func:`sum`："

#: ../../tutorial/controlflow.rst:154

msgid ""

">>> sum(range(4)) # 0 + 1 + 2 + 3\n"

"6"

msgstr ""

">>> sum(range(4)) # 0 + 1 + 2 + 3\n"

"6"

#: ../../tutorial/controlflow.rst:157

msgid ""

"Later we will see more functions that return iterables and take iterables as"

" arguments. In chapter :ref:`tut-structures`, we will discuss :func:`list` "

"in more detail."

msgstr ""

"后续我们会看到更多返回可迭代对象并以可迭代对象作为参数的函数。 在 :ref:`tut-structures` 一章中，我们将讨论 "

":func:`list` 的更多细节。"

#: ../../tutorial/controlflow.rst:164

msgid ":keyword:`!break` and :keyword:`!continue` Statements"

msgstr ":keyword:`!break` 和 :keyword:`!continue` 语句"

#: ../../tutorial/controlflow.rst:166

msgid ""

"The :keyword:`break` statement breaks out of the innermost enclosing "

":keyword:`for` or :keyword:`while` loop::"

msgstr ":keyword:`break` 语句将跳出最近的一层 :keyword:`for` 或 :keyword:`while` 循环::"

#: ../../tutorial/controlflow.rst:169

msgid ""

">>> for n in range(2, 10):\n"

"... for x in range(2, n):\n"

"... if n % x == 0:\n"

"... print(f\"{n} equals {x} * {n//x}\")\n"

"... break\n"

"...\n"

"4 equals 2 * 2\n"

"6 equals 2 * 3\n"

"8 equals 2 * 4\n"

"9 equals 3 * 3"

msgstr ""

">>> for n in range(2, 10):\n"

"... for x in range(2, n):\n"

"... if n % x == 0:\n"

"... print(f\"{n} equals {x} * {n//x}\")\n"

"... break\n"

"...\n"

"4 equals 2 * 2\n"

"6 equals 2 * 3\n"

"8 equals 2 * 4\n"

"9 equals 3 * 3"

#: ../../tutorial/controlflow.rst:180

msgid ""

"The :keyword:`continue` statement continues with the next iteration of the "

"loop::"

msgstr ":keyword:`continue` 语句将继续执行循环的下一次迭代::"

#: ../../tutorial/controlflow.rst:183

msgid ""

">>> for num in range(2, 10):\n"

"... if num % 2 == 0:\n"

"... print(f\"Found an even number {num}\")\n"

"... continue\n"

"... print(f\"Found an odd number {num}\")\n"

"...\n"

"Found an even number 2\n"

"Found an odd number 3\n"

"Found an even number 4\n"

"Found an odd number 5\n"

"Found an even number 6\n"

"Found an odd number 7\n"

"Found an even number 8\n"

"Found an odd number 9"

msgstr ""

">>> for num in range(2, 10):\n"

"... if num % 2 == 0:\n"

"... print(f\"Found an even number {num}\")\n"

"... continue\n"

"... print(f\"Found an odd number {num}\")\n"

"...\n"

"Found an even number 2\n"

"Found an odd number 3\n"

"Found an even number 4\n"

"Found an odd number 5\n"

"Found an even number 6\n"

"Found an odd number 7\n"

"Found an even number 8\n"

"Found an odd number 9"

#: ../../tutorial/controlflow.rst:202

msgid ":keyword:`!else` Clauses on Loops"

msgstr "循环的 :keyword:`!else` 子句"

#: ../../tutorial/controlflow.rst:204

msgid ""

"In a :keyword:`!for` or :keyword:`!while` loop the :keyword:`!break` "

"statement may be paired with an :keyword:`!else` clause. If the loop "

"finishes without executing the :keyword:`!break`, the :keyword:`!else` "

"clause executes."

msgstr ""

"在 :keyword:`!for` 或 :keyword:`!while` 循环中 :keyword:`!break` 语句可能对应一个 "

":keyword:`!else` 子句。 如果循环在未执行 :keyword:`!break` 的情况下结束，:keyword:`!else` "

"子句将会执行。"

#: ../../tutorial/controlflow.rst:208

msgid ""

"In a :keyword:`for` loop, the :keyword:`!else` clause is executed after the "

"loop finishes its final iteration, that is, if no break occurred."

msgstr ""

"在 :keyword:`for` 循环中，:keyword:`!else` 子句会在循环结束其最后一次迭代之后，即未执行 break 的情况下被执行。"

#: ../../tutorial/controlflow.rst:211

msgid ""

"In a :keyword:`while` loop, it's executed after the loop's condition becomes"

" false."

msgstr "在 :keyword:`while` 循环中，它会在循环条件变为假值后执行。"

#: ../../tutorial/controlflow.rst:213

msgid ""

"In either kind of loop, the :keyword:`!else` clause is **not** executed if "

"the loop was terminated by a :keyword:`break`. Of course, other ways of "

"ending the loop early, such as a :keyword:`return` or a raised exception, "

"will also skip execution of the :keyword:`else` clause."

msgstr ""

"在这两类循环中，当在循环被 :keyword:`break` 终结时 :keyword:`!else` 子句 **不会** 被执行。 "

"当然，其他提前结束循环的方式，如 :keyword:`return` 或是引发异常，也会跳过 :keyword:`else` 子句的执行。"

#: ../../tutorial/controlflow.rst:218

msgid ""

"This is exemplified in the following :keyword:`!for` loop, which searches "

"for prime numbers::"

msgstr "下面的搜索质数的 :keyword:`!for` 循环就是一个例子："

#: ../../tutorial/controlflow.rst:221

msgid ""

">>> for n in range(2, 10):\n"

"... for x in range(2, n):\n"

"... if n % x == 0:\n"

"... print(n, 'equals', x, '*', n//x)\n"

"... break\n"

"... else:\n"

"... # loop fell through without finding a factor\n"

"... print(n, 'is a prime number')\n"

"...\n"

"2 is a prime number\n"

"3 is a prime number\n"

"4 equals 2 * 2\n"

"5 is a prime number\n"

"6 equals 2 * 3\n"

"7 is a prime number\n"

"8 equals 2 * 4\n"

"9 equals 3 * 3"

msgstr ""

">>> for n in range(2, 10):\n"

"... for x in range(2, n):\n"

"... if n % x == 0:\n"

"... print(n, 'equals', x, '*', n//x)\n"

"... break\n"

"... else:\n"

"... # 循环到底未找到一个因数\n"

"... print(n, 'is a prime number')\n"

"...\n"

"2 is a prime number\n"

"3 is a prime number\n"

"4 equals 2 * 2\n"

"5 is a prime number\n"

"6 equals 2 * 3\n"

"7 is a prime number\n"

"8 equals 2 * 4\n"

"9 equals 3 * 3"

#: ../../tutorial/controlflow.rst:239

msgid ""

"(Yes, this is the correct code. Look closely: the ``else`` clause belongs "

"to the ``for`` loop, **not** the ``if`` statement.)"

msgstr "（对，这是正确的代码。 仔细看：其中 ``else`` 子句属于 ``for`` 循环，而 **不属于** ``if`` 语句。）"

#: ../../tutorial/controlflow.rst:242

msgid ""

"One way to think of the else clause is to imagine it paired with the ``if`` "

"inside the loop. As the loop executes, it will run a sequence like "

"if/if/if/else. The ``if`` is inside the loop, encountered a number of times."

" If the condition is ever true, a ``break`` will happen. If the condition is"

" never true, the ``else`` clause outside the loop will execute."

msgstr ""

"分析 else 子句的一种方式是想象它对应于循环内的 ``if``。 当循环执行时，它将运行一系列的 if/if/if/else。 ``if`` "

"位于循环内部，会出现多次。 当出现条件为真的情况时，将发生 ``break``。 如果条件一直不为真，则循环外的 ``else`` 子句将被执行。"

#: ../../tutorial/controlflow.rst:248

msgid ""

"When used with a loop, the ``else`` clause has more in common with the "

"``else`` clause of a :keyword:`try` statement than it does with that of "

"``if`` statements: a ``try`` statement's ``else`` clause runs when no "

"exception occurs, and a loop's ``else`` clause runs when no ``break`` "

"occurs. For more on the ``try`` statement and exceptions, see :ref:`tut-"

"handling`."

msgstr ""

"当配合循环使用时，``else`` 子句更像是 :keyword:`try` 语句的 ``else`` 子句而不像 ``if`` 语句的相应子句：一个 "

"``try`` 语句的 ``else`` 子句会在未发生异常时运行，而一个循环的 ``else`` 子句会在未发生 ``break`` 时运行。 有关 "

"``try`` 语句和异常的详情，请参阅 :ref:`tut-handling`。"

#: ../../tutorial/controlflow.rst:258

msgid ":keyword:`!pass` Statements"

msgstr ":keyword:`!pass` 语句"

#: ../../tutorial/controlflow.rst:260

msgid ""

"The :keyword:`pass` statement does nothing. It can be used when a statement "

"is required syntactically but the program requires no action. For example::"

msgstr ":keyword:`pass` 语句不执行任何动作。语法上需要一个语句，但程序毋需执行任何动作时，可以使用该语句。例如："

#: ../../tutorial/controlflow.rst:263

msgid ""

">>> while True:\n"

"... pass # Busy-wait for keyboard interrupt (Ctrl+C)\n"

"..."

msgstr ""

">>> while True:\n"

"... pass # 无限等待键盘中断 (Ctrl+C)\n"

"..."

#: ../../tutorial/controlflow.rst:267

msgid "This is commonly used for creating minimal classes::"

msgstr "这常用于创建一个最小的类："

#: ../../tutorial/controlflow.rst:269

msgid ""

">>> class MyEmptyClass:\n"

"... pass\n"

"..."

msgstr ""

">>> class MyEmptyClass:\n"

"... pass\n"

"..."

#: ../../tutorial/controlflow.rst:273

msgid ""

"Another place :keyword:`pass` can be used is as a place-holder for a "

"function or conditional body when you are working on new code, allowing you "

"to keep thinking at a more abstract level. The :keyword:`!pass` is silently"

" ignored::"

msgstr ""

":keyword:`pass` 还可用作函数或条件语句体的占位符，让你保持在更抽象的层次进行思考。:keyword:`!pass` 会被默默地忽略："

#: ../../tutorial/controlflow.rst:277

msgid ""

">>> def initlog(*args):\n"

"... pass # Remember to implement this!\n"

"..."

msgstr ""

">>> def initlog(*args):\n"

"... pass # 记得实现这个！\n"

"..."

#: ../../tutorial/controlflow.rst:281

msgid ""

"For this last case, many people use the ellipsis literal :code:`...` instead"

" of :code:`pass`. This use has no special meaning to Python, and is not part"

" of the language definition (you could use any constant expression here), "

"but :code:`...` is used conventionally as a placeholder body as well. See "

":ref:`bltin-ellipsis-object`."

msgstr ""

"对于这后一种情况，许多人会使用省略符字面值 :code:`...` 而不是 :code:`pass`。 这种用法在 Python "

"中没有特殊含义，也不是语言定义的一部分（这里你可以使用任意常量表达式），但 :code:`...` 在传统上也被用作占位符号。 参见 "

":ref:`bltin-ellipsis-object`。"

#: ../../tutorial/controlflow.rst:291

msgid ":keyword:`!match` Statements"

msgstr ":keyword:`!match` 语句"

#: ../../tutorial/controlflow.rst:293

msgid ""

"A :keyword:`match` statement takes an expression and compares its value to "

"successive patterns given as one or more case blocks. This is superficially"

" similar to a switch statement in C, Java or JavaScript (and many other "

"languages), but it's more similar to pattern matching in languages like Rust"

" or Haskell. Only the first pattern that matches gets executed and it can "

"also extract components (sequence elements or object attributes) from the "

"value into variables. If no case matches, none of the branches is executed."

msgstr ""

":keyword:`match` 语句接受一个表达式并把它的值与一个或多个 case 块给出的一系列模式进行比较。这表面上像 C、Java 或 "

"JavaScript（以及许多其他程序设计语言）中的 switch 语句，但其实它更像 Rust 或 Haskell "

"中的模式匹配。只有第一个匹配的模式会被执行，并且它还可以提取值的组成部分（序列的元素或对象的属性）赋给变量。如果没有匹配的case，则不执行任何分支。"

#: ../../tutorial/controlflow.rst:302

msgid ""

"The simplest form compares a subject value against one or more literals::"

msgstr "最简单的形式是将一个主语值与一个或多个字面值进行比较："

#: ../../tutorial/controlflow.rst:304

msgid ""

"def http_error(status):\n"

" match status:\n"

" case 400:\n"

" return \"Bad request\"\n"

" case 404:\n"

" return \"Not found\"\n"

" case 418:\n"

" return \"I'm a teapot\"\n"

" case _:\n"

" return \"Something's wrong with the internet\""

msgstr ""

"def http_error(status):\n"

" match status:\n"

" case 400:\n"

" return \"Bad request\"\n"

" case 404:\n"

" return \"Not found\"\n"

" case 418:\n"

" return \"I'm a teapot\"\n"

" case _:\n"

" return \"Something's wrong with the internet\""

#: ../../tutorial/controlflow.rst:315

msgid ""

"Note the last block: the \"variable name\" ``_`` acts as a *wildcard* and "

"never fails to match."

msgstr "注意最后一个代码块：“变量名” ``_`` 被作为 *通配符* 并必定会匹配成功。"

#: ../../tutorial/controlflow.rst:318

msgid ""

"You can combine several literals in a single pattern using ``|`` (\"or\")::"

msgstr "你可以用 ``|`` （“或”）将多个字面值组合到一个模式中："

#: ../../tutorial/controlflow.rst:320

msgid ""

"case 401 | 403 | 404:\n"

" return \"Not allowed\""

msgstr ""

"case 401 | 403 | 404:\n"

" return \"Not allowed\""

#: ../../tutorial/controlflow.rst:323

msgid ""

"Patterns can look like unpacking assignments, and can be used to bind "

"variables::"

msgstr "形如解包赋值的模式可被用于绑定变量："

#: ../../tutorial/controlflow.rst:326

msgid ""

"# point is an (x, y) tuple\n"

"match point:\n"

" case (0, 0):\n"

" print(\"Origin\")\n"

" case (0, y):\n"

" print(f\"Y={y}\")\n"

" case (x, 0):\n"

" print(f\"X={x}\")\n"

" case (x, y):\n"

" print(f\"X={x}, Y={y}\")\n"

" case _:\n"

" raise ValueError(\"Not a point\")"

msgstr ""

"# point 是一个 (x, y) 元组\n"

"match point:\n"

" case (0, 0):\n"

" print(\"Origin\")\n"

" case (0, y):\n"

" print(f\"Y={y}\")\n"

" case (x, 0):\n"

" print(f\"X={x}\")\n"

" case (x, y):\n"

" print(f\"X={x}, Y={y}\")\n"

" case _:\n"

" raise ValueError(\"Not a point\")"

#: ../../tutorial/controlflow.rst:339

msgid ""

"Study that one carefully! The first pattern has two literals, and can be "

"thought of as an extension of the literal pattern shown above. But the next"

" two patterns combine a literal and a variable, and the variable *binds* a "

"value from the subject (``point``). The fourth pattern captures two values,"

" which makes it conceptually similar to the unpacking assignment ``(x, y) = "

"point``."

msgstr ""

"请仔细学习此代码！第一个模式有两个字面值，可视为前述字面值模式的扩展。接下来的两个模式结合了一个字面值和一个变量，变量 *绑定* "

"了来自主语（``point``）的一个值。第四个模式捕获了两个值，使其在概念上与解包赋值 ``(x, y) = point`` 类似。"

#: ../../tutorial/controlflow.rst:346

msgid ""

"If you are using classes to structure your data you can use the class name "

"followed by an argument list resembling a constructor, but with the ability "

"to capture attributes into variables::"

msgstr "如果用类组织数据，可以用“类名后接一个参数列表”这种很像构造器的形式，把属性捕获到变量里："

#: ../../tutorial/controlflow.rst:350

msgid ""

"class Point:\n"

" def __init__(self, x, y):\n"

" self.x = x\n"

" self.y = y\n"

"\n"

"def where_is(point):\n"

" match point:\n"

" case Point(x=0, y=0):\n"

" print(\"Origin\")\n"

" case Point(x=0, y=y):\n"

" print(f\"Y={y}\")\n"

" case Point(x=x, y=0):\n"

" print(f\"X={x}\")\n"

" case Point():\n"

" print(\"Somewhere else\")\n"

" case _:\n"

" print(\"Not a point\")"

msgstr ""

"class Point:\n"

" def __init__(self, x, y):\n"

" self.x = x\n"

" self.y = y\n"

"\n"

"def where_is(point):\n"

" match point:\n"

" case Point(x=0, y=0):\n"

" print(\"Origin\")\n"

" case Point(x=0, y=y):\n"

" print(f\"Y={y}\")\n"

" case Point(x=x, y=0):\n"

" print(f\"X={x}\")\n"

" case Point():\n"

" print(\"Somewhere else\")\n"

" case _:\n"

" print(\"Not a point\")"

#: ../../tutorial/controlflow.rst:368

msgid ""

"You can use positional parameters with some builtin classes that provide an "

"ordering for their attributes (e.g. dataclasses). You can also define a "

"specific position for attributes in patterns by setting the "

"``__match_args__`` special attribute in your classes. If it's set to (\"x\","

" \"y\"), the following patterns are all equivalent (and all bind the ``y`` "

"attribute to the ``var`` variable)::"

msgstr ""

"一些内置类（如 dataclass）为属性提供了一个顺序，此时，可以使用位置参数。自定义类可通过在类中设置特殊属性 "

"``__match_args__``，为属性指定其在模式中对应的位置。若设为 (\"x\", \"y\")，则以下模式相互等价（且都把属性 ``y`` "

"绑定到变量 ``var``）："

#: ../../tutorial/controlflow.rst:374

msgid ""

"Point(1, var)\n"

"Point(1, y=var)\n"

"Point(x=1, y=var)\n"

"Point(y=var, x=1)"

msgstr ""

"Point(1, var)\n"

"Point(1, y=var)\n"

"Point(x=1, y=var)\n"

"Point(y=var, x=1)"

#: ../../tutorial/controlflow.rst:379

msgid ""

"A recommended way to read patterns is to look at them as an extended form of"

" what you would put on the left of an assignment, to understand which "

"variables would be set to what. Only the standalone names (like ``var`` "

"above) are assigned to by a match statement. Dotted names (like "

"``foo.bar``), attribute names (the ``x=`` and ``y=`` above) or class names "

"(recognized by the \"(...)\" next to them like ``Point`` above) are never "

"assigned to."

msgstr ""

"建议这样来阅读一个模式——通过将其视为赋值语句等号左边的一种扩展形式，来理解各个变量被设为何值。match 语句只会为单一的名称（如上面的 "

"``var``）赋值，而不会赋值给带点号的名称（如 ``foo.bar``）、属性名（如上面的 ``x=`` 和 ``y=``）和类名（是通过其后的 "

"\"(...)\" 来识别的，如上面的 ``Point``）。"

#: ../../tutorial/controlflow.rst:386

msgid ""

"Patterns can be arbitrarily nested. For example, if we have a short list of"

" Points, with ``__match_args__`` added, we could match it like this::"

msgstr ""

"模式可以任意嵌套。举例来说，如果我们有一个由 Point 组成的列表，且 Point 添加了 ``__match_args__`` "

"时，我们可以这样来匹配它："

#: ../../tutorial/controlflow.rst:389

msgid ""

"class Point:\n"

" __match_args__ = ('x', 'y')\n"

" def __init__(self, x, y):\n"

" self.x = x\n"

" self.y = y\n"

"\n"

"match points:\n"

" case []:\n"

" print(\"No points\")\n"

" case [Point(0, 0)]:\n"

" print(\"The origin\")\n"

" case [Point(x, y)]:\n"

" print(f\"Single point {x}, {y}\")\n"

" case [Point(0, y1), Point(0, y2)]:\n"

" print(f\"Two on the Y axis at {y1}, {y2}\")\n"

" case _:\n"

" print(\"Something else\")"

msgstr ""

"class Point:\n"

" __match_args__ = ('x', 'y')\n"

" def __init__(self, x, y):\n"

" self.x = x\n"

" self.y = y\n"

"\n"

"match points:\n"

" case []:\n"

" print(\"No points\")\n"

" case [Point(0, 0)]:\n"

" print(\"The origin\")\n"

" case [Point(x, y)]:\n"

" print(f\"Single point {x}, {y}\")\n"

" case [Point(0, y1), Point(0, y2)]:\n"

" print(f\"Two on the Y axis at {y1}, {y2}\")\n"

" case _:\n"

" print(\"Something else\")"

#: ../../tutorial/controlflow.rst:407

msgid ""

"We can add an ``if`` clause to a pattern, known as a \"guard\". If the "

"guard is false, ``match`` goes on to try the next case block. Note that "

"value capture happens before the guard is evaluated::"

msgstr ""

"我们可以为模式添加 ``if`` 作为守卫子句。如果守卫子句的值为假，那么 ``match`` 会继续尝试匹配下一个 case "

"块。注意是先将值捕获，再对守卫子句求值："

#: ../../tutorial/controlflow.rst:411

msgid ""

"match point:\n"

" case Point(x, y) if x == y:\n"

" print(f\"Y=X at {x}\")\n"

" case Point(x, y):\n"

" print(f\"Not on the diagonal\")"

msgstr ""

"match point:\n"

" case Point(x, y) if x == y:\n"

" print(f\"Y=X at {x}\")\n"

" case Point(x, y):\n"

" print(f\"Not on the diagonal\")"

#: ../../tutorial/controlflow.rst:417

msgid "Several other key features of this statement:"

msgstr "该语句的一些其它关键特性："

#: ../../tutorial/controlflow.rst:419

msgid ""

"Like unpacking assignments, tuple and list patterns have exactly the same "

"meaning and actually match arbitrary sequences. An important exception is "

"that they don't match iterators or strings."

msgstr "与解包赋值类似，元组和列表模式具有完全相同的含义并且实际上都能匹配任意序列，区别是它们不能匹配迭代器或字符串。"

#: ../../tutorial/controlflow.rst:423

msgid ""

"Sequence patterns support extended unpacking: ``[x, y, *rest]`` and ``(x, y,"

" *rest)`` work similar to unpacking assignments. The name after ``*`` may "

"also be ``_``, so ``(x, y, *_)`` matches a sequence of at least two items "

"without binding the remaining items."

msgstr ""

"序列模式支持扩展解包：``[x, y, *rest]`` 和 ``(x, y, *rest)`` 和相应的解包赋值做的事是一样的。接在 ``*`` "

"后的名称也可以为 ``_``，所以 ``(x, y, *_)`` 匹配含至少两项的序列，而不必绑定剩余的项。"

#: ../../tutorial/controlflow.rst:428

msgid ""

"Mapping patterns: ``{\"bandwidth\": b, \"latency\": l}`` captures the "

"``\"bandwidth\"`` and ``\"latency\"`` values from a dictionary. Unlike "

"sequence patterns, extra keys are ignored. An unpacking like ``**rest`` is "

"also supported. (But ``**_`` would be redundant, so it is not allowed.)"

msgstr ""

"映射模式：``{\"bandwidth\": b, \"latency\": l}`` 从字典中捕获 ``\"bandwidth\"`` 和 "

"``\"latency\"`` 的值。额外的键会被忽略，这一点与序列模式不同。``**rest`` 这样的解包也支持。（但 ``**_`` "

"将会是冗余的，故不允许使用。）"

#: ../../tutorial/controlflow.rst:433

msgid "Subpatterns may be captured using the ``as`` keyword::"

msgstr "使用 ``as`` 关键字可以捕获子模式："

#: ../../tutorial/controlflow.rst:435

msgid "case (Point(x1, y1), Point(x2, y2) as p2): ..."

msgstr "case (Point(x1, y1), Point(x2, y2) as p2): ..."

#: ../../tutorial/controlflow.rst:437

msgid ""

"will capture the second element of the input as ``p2`` (as long as the input"

" is a sequence of two points)"

msgstr "将把输入中的第二个元素捕获为 ``p2`` （只要输入是包含两个点的序列）"

#: ../../tutorial/controlflow.rst:440

msgid ""

"Most literals are compared by equality, however the singletons ``True``, "

"``False`` and ``None`` are compared by identity."

msgstr "大多数字面值是按相等性比较的，但是单例对象 ``True``、``False`` 和 ``None`` 则是按 id 比较的。"

#: ../../tutorial/controlflow.rst:443

msgid ""

"Patterns may use named constants. These must be dotted names to prevent "

"them from being interpreted as capture variables::"

msgstr "模式可以使用具名常量。 它们必须为带点号的名称以防止它们被解读为捕获变量::"

#: ../../tutorial/controlflow.rst:446

msgid ""

"from enum import Enum\n"

"class Color(Enum):\n"

" RED = 'red'\n"

" GREEN = 'green'\n"

" BLUE = 'blue'\n"

"\n"

"color = Color(input(\"Enter your choice of 'red', 'blue' or 'green': \"))\n"

"\n"

"match color:\n"

" case Color.RED:\n"

" print(\"I see red!\")\n"

" case Color.GREEN:\n"

" print(\"Grass is green\")\n"

" case Color.BLUE:\n"

" print(\"I'm feeling the blues :(\")"

msgstr ""

"from enum import Enum\n"

"class Color(Enum):\n"

" RED = 'red'\n"

" GREEN = 'green'\n"

" BLUE = 'blue'\n"

"\n"

"color = Color(input(\"Enter your choice of 'red', 'blue' or 'green': \"))\n"

"\n"

"match color:\n"

" case Color.RED:\n"

" print(\"I see red!\")\n"

" case Color.GREEN:\n"

" print(\"Grass is green\")\n"

" case Color.BLUE:\n"

" print(\"I'm feeling the blues :(\")"

#: ../../tutorial/controlflow.rst:462

msgid ""

"For a more detailed explanation and additional examples, you can look into "

":pep:`636` which is written in a tutorial format."

msgstr "更详细的说明和更多示例，可参阅以教程格式撰写的 :pep:`636`。"

#: ../../tutorial/controlflow.rst:468

msgid "Defining Functions"

msgstr "定义函数"

#: ../../tutorial/controlflow.rst:470

msgid ""

"We can create a function that writes the Fibonacci series to an arbitrary "

"boundary::"

msgstr "下列代码创建一个可以输出限定数值内的斐波那契数列函数："

#: ../../tutorial/controlflow.rst:473

msgid ""

">>> def fib(n): # write Fibonacci series less than n\n"

"... \"\"\"Print a Fibonacci series less than n.\"\"\"\n"

"... a, b = 0, 1\n"

"... while a < n:\n"

"... print(a, end=' ')\n"

"... a, b = b, a+b\n"

"... print()\n"

"...\n"

">>> # Now call the function we just defined:\n"

">>> fib(2000)\n"

"0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597"

msgstr ""

">>> def fib(n): # 打印小于 n 的斐波那契数列\n"

"... \"\"\"Print a Fibonacci series less than n.\"\"\"\n"

"... a, b = 0, 1\n"

"... while a < n:\n"

"... print(a, end=' ')\n"

"... a, b = b, a+b\n"

"... print()\n"

"...\n"

">>> # 现在调用我们刚定义的函数：\n"

">>> fib(2000)\n"

"0 1 1 2 3 5 8 13 21 34 55 89 144 233 377 610 987 1597"

#: ../../tutorial/controlflow.rst:490

msgid ""

"The keyword :keyword:`def` introduces a function *definition*. It must be "

"followed by the function name and the parenthesized list of formal "

"parameters. The statements that form the body of the function start at the "

"next line, and must be indented."

msgstr "*定义* 函数使用关键字 :keyword:`def`，后跟函数名与括号内的形参列表。函数语句从下一行开始，并且必须缩进。"

#: ../../tutorial/controlflow.rst:495

msgid ""

"The first statement of the function body can optionally be a string literal;"

" this string literal is the function's documentation string, or "

":dfn:`docstring`. (More about docstrings can be found in the section "

":ref:`tut-docstrings`.) There are tools which use docstrings to "

"automatically produce online or printed documentation, or to let the user "

"interactively browse through code; it's good practice to include docstrings "

"in code that you write, so make a habit of it."

msgstr ""

"函数内的第一条语句是字符串时，该字符串就是文档字符串，也称为 :dfn:`docstring`，详见 :ref:`tut-"

"docstrings`。利用文档字符串可以自动生成在线文档或打印版文档，还可以让开发者在浏览代码时直接查阅文档；Python "

"开发者最好养成在代码中加入文档字符串的好习惯。"

#: ../../tutorial/controlflow.rst:502

msgid ""

"The *execution* of a function introduces a new symbol table used for the "

"local variables of the function. More precisely, all variable assignments "

"in a function store the value in the local symbol table; whereas variable "

"references first look in the local symbol table, then in the local symbol "

"tables of enclosing functions, then in the global symbol table, and finally "

"in the table of built-in names. Thus, global variables and variables of "

"enclosing functions cannot be directly assigned a value within a function "

"(unless, for global variables, named in a :keyword:`global` statement, or, "

"for variables of enclosing functions, named in a :keyword:`nonlocal` "

"statement), although they may be referenced."

msgstr ""

"函数在 *执行* "

"时使用函数局部变量符号表，所有函数变量赋值都存在局部符号表中；引用变量时，首先，在局部符号表里查找变量，然后，是外层函数局部符号表，再是全局符号表，最后是内置名称符号表。因此，尽管可以引用全局变量和外层函数的变量，但最好不要在函数内直接赋值（除非是"