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2349 lines (1967 loc) · 77.8 KB
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# SOME DESCRIPTIVE TITLE.
# Copyright (C) 2001-2022, Python Software Foundation
# This file is distributed under the same license as the Python package.
#
# Translators:
# jerrychen <jerrychen.ee@gmail.com>, 2016
# Ching-Lung Chuang, 2015
# hsiao yi <hsiaoyi0504@gmail.com>, 2016
msgid ""
msgstr ""
"Project-Id-Version: Python 3.10\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2022-10-05 00:24+0000\n"
"PO-Revision-Date: 2018-05-23 14:35+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"
#: ../../faq/programming.rst:5
msgid "Programming FAQ"
msgstr "程式開發常見問答集"
#: ../../faq/programming.rst:8
msgid "Contents"
msgstr "目錄"
#: ../../faq/programming.rst:12
msgid "General Questions"
msgstr "常見問題"
#: ../../faq/programming.rst:15
msgid ""
"Is there a source code level debugger with breakpoints, single-stepping, "
"etc.?"
msgstr "是否有可以使用在程式碼階段,具有中斷點,步驟執行等功能的除錯器？"
#: ../../faq/programming.rst:17 ../../faq/programming.rst:57
msgid "Yes."
msgstr "有的"
#: ../../faq/programming.rst:19
msgid ""
"Several debuggers for Python are described below, and the built-in function :"
"func:`breakpoint` allows you to drop into any of them."
msgstr ""
#: ../../faq/programming.rst:22
msgid ""
"The pdb module is a simple but adequate console-mode debugger for Python. It "
"is part of the standard Python library, and is :mod:`documented in the "
"Library Reference Manual <pdb>`. You can also write your own debugger by "
"using the code for pdb as an example."
msgstr ""
#: ../../faq/programming.rst:27
msgid ""
"The IDLE interactive development environment, which is part of the standard "
"Python distribution (normally available as Tools/scripts/idle), includes a "
"graphical debugger."
msgstr ""
#: ../../faq/programming.rst:31
msgid ""
"PythonWin is a Python IDE that includes a GUI debugger based on pdb. The "
"PythonWin debugger colors breakpoints and has quite a few cool features such "
"as debugging non-PythonWin programs. PythonWin is available as part of "
"`pywin32 <https://github.com/mhammond/pywin32>`_ project and as a part of "
"the `ActivePython <https://www.activestate.com/products/python/>`_ "
"distribution."
msgstr ""
#: ../../faq/programming.rst:38
msgid ""
"`Eric <https://eric-ide.python-projects.org/>`_ is an IDE built on PyQt and "
"the Scintilla editing component."
msgstr ""
#: ../../faq/programming.rst:41
msgid ""
"`trepan3k <https://github.com/rocky/python3-trepan/>`_ is a gdb-like "
"debugger."
msgstr ""
#: ../../faq/programming.rst:43
msgid ""
"`Visual Studio Code <https://code.visualstudio.com/>`_ is an IDE with "
"debugging tools that integrates with version-control software."
msgstr ""
#: ../../faq/programming.rst:46
msgid ""
"There are a number of commercial Python IDEs that include graphical "
"debuggers. They include:"
msgstr "有數個商業化Python整合化開發工具包含圖形除錯功能。這些包含："
#: ../../faq/programming.rst:49
msgid "`Wing IDE <https://wingware.com/>`_"
msgstr "`Wing IDE <https://wingware.com/>`_"
#: ../../faq/programming.rst:50
msgid "`Komodo IDE <https://www.activestate.com/products/komodo-ide/>`_"
msgstr "`Komodo IDE <https://www.activestate.com/products/komodo-ide/>`_"
#: ../../faq/programming.rst:51
msgid "`PyCharm <https://www.jetbrains.com/pycharm/>`_"
msgstr "`PyCharm <https://www.jetbrains.com/pycharm/>`_"
#: ../../faq/programming.rst:55
msgid "Are there tools to help find bugs or perform static analysis?"
msgstr "有沒有工具能夠幫忙找 bug 或執行靜態分析？"
#: ../../faq/programming.rst:59
msgid ""
"`Pylint <https://pylint.pycqa.org/en/latest/index.html>`_ and `Pyflakes "
"<https://github.com/PyCQA/pyflakes>`_ do basic checking that will help you "
"catch bugs sooner."
msgstr ""
#: ../../faq/programming.rst:63
msgid ""
"Static type checkers such as `Mypy <http://mypy-lang.org/>`_, `Pyre <https://"
"pyre-check.org/>`_, and `Pytype <https://github.com/google/pytype>`_ can "
"check type hints in Python source code."
msgstr ""
#: ../../faq/programming.rst:72
msgid "How can I create a stand-alone binary from a Python script?"
msgstr ""
#: ../../faq/programming.rst:74
msgid ""
"You don't need the ability to compile Python to C code if all you want is a "
"stand-alone program that users can download and run without having to "
"install the Python distribution first. There are a number of tools that "
"determine the set of modules required by a program and bind these modules "
"together with a Python binary to produce a single executable."
msgstr ""
#: ../../faq/programming.rst:80
msgid ""
"One is to use the freeze tool, which is included in the Python source tree "
"as ``Tools/freeze``. It converts Python byte code to C arrays; with a C "
"compiler you can embed all your modules into a new program, which is then "
"linked with the standard Python modules."
msgstr ""
#: ../../faq/programming.rst:85
msgid ""
"It works by scanning your source recursively for import statements (in both "
"forms) and looking for the modules in the standard Python path as well as in "
"the source directory (for built-in modules). It then turns the bytecode for "
"modules written in Python into C code (array initializers that can be turned "
"into code objects using the marshal module) and creates a custom-made config "
"file that only contains those built-in modules which are actually used in "
"the program. It then compiles the generated C code and links it with the "
"rest of the Python interpreter to form a self-contained binary which acts "
"exactly like your script."
msgstr ""
#: ../../faq/programming.rst:94
msgid ""
"The following packages can help with the creation of console and GUI "
"executables:"
msgstr ""
#: ../../faq/programming.rst:97
msgid "`Nuitka <https://nuitka.net/>`_ (Cross-platform)"
msgstr "`Nuitka <https://nuitka.net/>`_\\ （跨平台）"
#: ../../faq/programming.rst:98
msgid "`PyInstaller <https://pyinstaller.org/>`_ (Cross-platform)"
msgstr "`PyInstaller <https://pyinstaller.org/>`_\\ （跨平台）"
#: ../../faq/programming.rst:99
msgid ""
"`PyOxidizer <https://pyoxidizer.readthedocs.io/en/stable/>`_ (Cross-platform)"
msgstr ""
"`PyOxidizer <https://pyoxidizer.readthedocs.io/en/stable/>`_\\ （跨平台）"
#: ../../faq/programming.rst:100
msgid ""
"`cx_Freeze <https://marcelotduarte.github.io/cx_Freeze/>`_ (Cross-platform)"
msgstr ""
"`cx_Freeze <https://marcelotduarte.github.io/cx_Freeze/>`_\\ （跨平台）"
#: ../../faq/programming.rst:101
msgid "`py2app <https://github.com/ronaldoussoren/py2app>`_ (macOS only)"
msgstr "`py2app <https://github.com/ronaldoussoren/py2app>`_\\ （僅限 macOS）"
#: ../../faq/programming.rst:102
msgid "`py2exe <https://www.py2exe.org/>`_ (Windows only)"
msgstr "`py2exe <https://www.py2exe.org/>`_\\ （僅限 Windows）"
#: ../../faq/programming.rst:105
msgid "Are there coding standards or a style guide for Python programs?"
msgstr ""
#: ../../faq/programming.rst:107
msgid ""
"Yes. The coding style required for standard library modules is documented "
"as :pep:`8`."
msgstr ""
#: ../../faq/programming.rst:112
msgid "Core Language"
msgstr ""
#: ../../faq/programming.rst:115
msgid "Why am I getting an UnboundLocalError when the variable has a value?"
msgstr "為什麼當變數有值時我得到錯誤訊息 UnboundLocalError"
#: ../../faq/programming.rst:117
msgid ""
"It can be a surprise to get the UnboundLocalError in previously working code "
"when it is modified by adding an assignment statement somewhere in the body "
"of a function."
msgstr ""
#: ../../faq/programming.rst:121
msgid "This code:"
msgstr "這段程式碼:"
#: ../../faq/programming.rst:129
msgid "works, but this code:"
msgstr "可以執行,但是這段程式:"
#: ../../faq/programming.rst:136
msgid "results in an UnboundLocalError:"
msgstr "導致UnboundLocalError"
#: ../../faq/programming.rst:143
msgid ""
"This is because when you make an assignment to a variable in a scope, that "
"variable becomes local to that scope and shadows any similarly named "
"variable in the outer scope. Since the last statement in foo assigns a new "
"value to ``x``, the compiler recognizes it as a local variable. "
"Consequently when the earlier ``print(x)`` attempts to print the "
"uninitialized local variable and an error results."
msgstr ""
#: ../../faq/programming.rst:150
msgid ""
"In the example above you can access the outer scope variable by declaring it "
"global:"
msgstr ""
#: ../../faq/programming.rst:161
msgid ""
"This explicit declaration is required in order to remind you that (unlike "
"the superficially analogous situation with class and instance variables) you "
"are actually modifying the value of the variable in the outer scope:"
msgstr ""
#: ../../faq/programming.rst:168
msgid ""
"You can do a similar thing in a nested scope using the :keyword:`nonlocal` "
"keyword:"
msgstr ""
#: ../../faq/programming.rst:185
msgid "What are the rules for local and global variables in Python?"
msgstr "Python 的區域變數和全域變數有什麼規則？"
#: ../../faq/programming.rst:187
msgid ""
"In Python, variables that are only referenced inside a function are "
"implicitly global. If a variable is assigned a value anywhere within the "
"function's body, it's assumed to be a local unless explicitly declared as "
"global."
msgstr ""
#: ../../faq/programming.rst:191
msgid ""
"Though a bit surprising at first, a moment's consideration explains this. "
"On one hand, requiring :keyword:`global` for assigned variables provides a "
"bar against unintended side-effects. On the other hand, if ``global`` was "
"required for all global references, you'd be using ``global`` all the time. "
"You'd have to declare as global every reference to a built-in function or to "
"a component of an imported module. This clutter would defeat the usefulness "
"of the ``global`` declaration for identifying side-effects."
msgstr ""
#: ../../faq/programming.rst:201
msgid ""
"Why do lambdas defined in a loop with different values all return the same "
"result?"
msgstr ""
#: ../../faq/programming.rst:203
msgid ""
"Assume you use a for loop to define a few different lambdas (or even plain "
"functions), e.g.::"
msgstr ""
#: ../../faq/programming.rst:210
msgid ""
"This gives you a list that contains 5 lambdas that calculate ``x**2``. You "
"might expect that, when called, they would return, respectively, ``0``, "
"``1``, ``4``, ``9``, and ``16``. However, when you actually try you will "
"see that they all return ``16``::"
msgstr ""
#: ../../faq/programming.rst:220
msgid ""
"This happens because ``x`` is not local to the lambdas, but is defined in "
"the outer scope, and it is accessed when the lambda is called --- not when "
"it is defined. At the end of the loop, the value of ``x`` is ``4``, so all "
"the functions now return ``4**2``, i.e. ``16``. You can also verify this by "
"changing the value of ``x`` and see how the results of the lambdas change::"
msgstr ""
#: ../../faq/programming.rst:230
msgid ""
"In order to avoid this, you need to save the values in variables local to "
"the lambdas, so that they don't rely on the value of the global ``x``::"
msgstr ""
#: ../../faq/programming.rst:237
msgid ""
"Here, ``n=x`` creates a new variable ``n`` local to the lambda and computed "
"when the lambda is defined so that it has the same value that ``x`` had at "
"that point in the loop. This means that the value of ``n`` will be ``0`` in "
"the first lambda, ``1`` in the second, ``2`` in the third, and so on. "
"Therefore each lambda will now return the correct result::"
msgstr ""
#: ../../faq/programming.rst:248
msgid ""
"Note that this behaviour is not peculiar to lambdas, but applies to regular "
"functions too."
msgstr ""
#: ../../faq/programming.rst:253
msgid "How do I share global variables across modules?"
msgstr ""
#: ../../faq/programming.rst:255
msgid ""
"The canonical way to share information across modules within a single "
"program is to create a special module (often called config or cfg). Just "
"import the config module in all modules of your application; the module then "
"becomes available as a global name. Because there is only one instance of "
"each module, any changes made to the module object get reflected "
"everywhere. For example:"
msgstr ""
#: ../../faq/programming.rst:261
msgid "config.py::"
msgstr ""
"config.py：\n"
"\n"
"::"
#: ../../faq/programming.rst:265
msgid "mod.py::"
msgstr ""
"mod.py：\n"
"\n"
"::"
#: ../../faq/programming.rst:270
msgid "main.py::"
msgstr ""
"main.py：\n"
"\n"
"::"
#: ../../faq/programming.rst:276
msgid ""
"Note that using a module is also the basis for implementing the Singleton "
"design pattern, for the same reason."
msgstr ""
#: ../../faq/programming.rst:281
msgid "What are the \"best practices\" for using import in a module?"
msgstr ""
#: ../../faq/programming.rst:283
msgid ""
"In general, don't use ``from modulename import *``. Doing so clutters the "
"importer's namespace, and makes it much harder for linters to detect "
"undefined names."
msgstr ""
#: ../../faq/programming.rst:287
msgid ""
"Import modules at the top of a file. Doing so makes it clear what other "
"modules your code requires and avoids questions of whether the module name "
"is in scope. Using one import per line makes it easy to add and delete "
"module imports, but using multiple imports per line uses less screen space."
msgstr ""
#: ../../faq/programming.rst:292
msgid "It's good practice if you import modules in the following order:"
msgstr ""
#: ../../faq/programming.rst:294
msgid "standard library modules -- e.g. ``sys``, ``os``, ``getopt``, ``re``"
msgstr ""
#: ../../faq/programming.rst:295
msgid ""
"third-party library modules (anything installed in Python's site-packages "
"directory) -- e.g. mx.DateTime, ZODB, PIL.Image, etc."
msgstr ""
#: ../../faq/programming.rst:297
msgid "locally developed modules"
msgstr ""
#: ../../faq/programming.rst:299
msgid ""
"It is sometimes necessary to move imports to a function or class to avoid "
"problems with circular imports. Gordon McMillan says:"
msgstr ""
#: ../../faq/programming.rst:302
msgid ""
"Circular imports are fine where both modules use the \"import <module>\" "
"form of import. They fail when the 2nd module wants to grab a name out of "
"the first (\"from module import name\") and the import is at the top level. "
"That's because names in the 1st are not yet available, because the first "
"module is busy importing the 2nd."
msgstr ""
#: ../../faq/programming.rst:308
msgid ""
"In this case, if the second module is only used in one function, then the "
"import can easily be moved into that function. By the time the import is "
"called, the first module will have finished initializing, and the second "
"module can do its import."
msgstr ""
#: ../../faq/programming.rst:313
msgid ""
"It may also be necessary to move imports out of the top level of code if "
"some of the modules are platform-specific. In that case, it may not even be "
"possible to import all of the modules at the top of the file. In this case, "
"importing the correct modules in the corresponding platform-specific code is "
"a good option."
msgstr ""
#: ../../faq/programming.rst:318
msgid ""
"Only move imports into a local scope, such as inside a function definition, "
"if it's necessary to solve a problem such as avoiding a circular import or "
"are trying to reduce the initialization time of a module. This technique is "
"especially helpful if many of the imports are unnecessary depending on how "
"the program executes. You may also want to move imports into a function if "
"the modules are only ever used in that function. Note that loading a module "
"the first time may be expensive because of the one time initialization of "
"the module, but loading a module multiple times is virtually free, costing "
"only a couple of dictionary lookups. Even if the module name has gone out "
"of scope, the module is probably available in :data:`sys.modules`."
msgstr ""
#: ../../faq/programming.rst:331
msgid "Why are default values shared between objects?"
msgstr ""
#: ../../faq/programming.rst:333
msgid ""
"This type of bug commonly bites neophyte programmers. Consider this "
"function::"
msgstr ""
#: ../../faq/programming.rst:340
msgid ""
"The first time you call this function, ``mydict`` contains a single item. "
"The second time, ``mydict`` contains two items because when ``foo()`` begins "
"executing, ``mydict`` starts out with an item already in it."
msgstr ""
#: ../../faq/programming.rst:344
msgid ""
"It is often expected that a function call creates new objects for default "
"values. This is not what happens. Default values are created exactly once, "
"when the function is defined. If that object is changed, like the "
"dictionary in this example, subsequent calls to the function will refer to "
"this changed object."
msgstr ""
#: ../../faq/programming.rst:349
msgid ""
"By definition, immutable objects such as numbers, strings, tuples, and "
"``None``, are safe from change. Changes to mutable objects such as "
"dictionaries, lists, and class instances can lead to confusion."
msgstr ""
#: ../../faq/programming.rst:353
msgid ""
"Because of this feature, it is good programming practice to not use mutable "
"objects as default values. Instead, use ``None`` as the default value and "
"inside the function, check if the parameter is ``None`` and create a new "
"list/dictionary/whatever if it is. For example, don't write::"
msgstr ""
#: ../../faq/programming.rst:361
msgid "but::"
msgstr ""
"但是：\n"
"\n"
"::"
#: ../../faq/programming.rst:367
msgid ""
"This feature can be useful. When you have a function that's time-consuming "
"to compute, a common technique is to cache the parameters and the resulting "
"value of each call to the function, and return the cached value if the same "
"value is requested again. This is called \"memoizing\", and can be "
"implemented like this::"
msgstr ""
#: ../../faq/programming.rst:382
msgid ""
"You could use a global variable containing a dictionary instead of the "
"default value; it's a matter of taste."
msgstr ""
#: ../../faq/programming.rst:387
msgid ""
"How can I pass optional or keyword parameters from one function to another?"
msgstr ""
#: ../../faq/programming.rst:389
msgid ""
"Collect the arguments using the ``*`` and ``**`` specifiers in the "
"function's parameter list; this gives you the positional arguments as a "
"tuple and the keyword arguments as a dictionary. You can then pass these "
"arguments when calling another function by using ``*`` and ``**``::"
msgstr ""
#: ../../faq/programming.rst:408
msgid "What is the difference between arguments and parameters?"
msgstr ""
#: ../../faq/programming.rst:410
msgid ""
":term:`Parameters <parameter>` are defined by the names that appear in a "
"function definition, whereas :term:`arguments <argument>` are the values "
"actually passed to a function when calling it. Parameters define what :term:"
"`kind of arguments <parameter>` a function can accept. For example, given "
"the function definition::"
msgstr ""
#: ../../faq/programming.rst:419
msgid ""
"*foo*, *bar* and *kwargs* are parameters of ``func``. However, when calling "
"``func``, for example::"
msgstr ""
#: ../../faq/programming.rst:424
msgid "the values ``42``, ``314``, and ``somevar`` are arguments."
msgstr ""
#: ../../faq/programming.rst:428
msgid "Why did changing list 'y' also change list 'x'?"
msgstr ""
#: ../../faq/programming.rst:430
msgid "If you wrote code like::"
msgstr ""
#: ../../faq/programming.rst:440
msgid ""
"you might be wondering why appending an element to ``y`` changed ``x`` too."
msgstr ""
#: ../../faq/programming.rst:442
msgid "There are two factors that produce this result:"
msgstr ""
#: ../../faq/programming.rst:444
msgid ""
"Variables are simply names that refer to objects. Doing ``y = x`` doesn't "
"create a copy of the list -- it creates a new variable ``y`` that refers to "
"the same object ``x`` refers to. This means that there is only one object "
"(the list), and both ``x`` and ``y`` refer to it."
msgstr ""
#: ../../faq/programming.rst:448
msgid ""
"Lists are :term:`mutable`, which means that you can change their content."
msgstr ""
#: ../../faq/programming.rst:450
msgid ""
"After the call to :meth:`~list.append`, the content of the mutable object "
"has changed from ``[]`` to ``[10]``. Since both the variables refer to the "
"same object, using either name accesses the modified value ``[10]``."
msgstr ""
#: ../../faq/programming.rst:454
msgid "If we instead assign an immutable object to ``x``::"
msgstr ""
#: ../../faq/programming.rst:464
msgid ""
"we can see that in this case ``x`` and ``y`` are not equal anymore. This is "
"because integers are :term:`immutable`, and when we do ``x = x + 1`` we are "
"not mutating the int ``5`` by incrementing its value; instead, we are "
"creating a new object (the int ``6``) and assigning it to ``x`` (that is, "
"changing which object ``x`` refers to). After this assignment we have two "
"objects (the ints ``6`` and ``5``) and two variables that refer to them "
"(``x`` now refers to ``6`` but ``y`` still refers to ``5``)."
msgstr ""
#: ../../faq/programming.rst:472
msgid ""
"Some operations (for example ``y.append(10)`` and ``y.sort()``) mutate the "
"object, whereas superficially similar operations (for example ``y = y + "
"[10]`` and ``sorted(y)``) create a new object. In general in Python (and in "
"all cases in the standard library) a method that mutates an object will "
"return ``None`` to help avoid getting the two types of operations confused. "
"So if you mistakenly write ``y.sort()`` thinking it will give you a sorted "
"copy of ``y``, you'll instead end up with ``None``, which will likely cause "
"your program to generate an easily diagnosed error."
msgstr ""
#: ../../faq/programming.rst:481
msgid ""
"However, there is one class of operations where the same operation sometimes "
"has different behaviors with different types: the augmented assignment "
"operators. For example, ``+=`` mutates lists but not tuples or ints "
"(``a_list += [1, 2, 3]`` is equivalent to ``a_list.extend([1, 2, 3])`` and "
"mutates ``a_list``, whereas ``some_tuple += (1, 2, 3)`` and ``some_int += "
"1`` create new objects)."
msgstr ""
#: ../../faq/programming.rst:488
msgid "In other words:"
msgstr ""
#: ../../faq/programming.rst:490
msgid ""
"If we have a mutable object (:class:`list`, :class:`dict`, :class:`set`, "
"etc.), we can use some specific operations to mutate it and all the "
"variables that refer to it will see the change."
msgstr ""
#: ../../faq/programming.rst:493
msgid ""
"If we have an immutable object (:class:`str`, :class:`int`, :class:`tuple`, "
"etc.), all the variables that refer to it will always see the same value, "
"but operations that transform that value into a new value always return a "
"new object."
msgstr ""
#: ../../faq/programming.rst:498
msgid ""
"If you want to know if two variables refer to the same object or not, you "
"can use the :keyword:`is` operator, or the built-in function :func:`id`."
msgstr ""
#: ../../faq/programming.rst:503
msgid "How do I write a function with output parameters (call by reference)?"
msgstr ""
#: ../../faq/programming.rst:505
msgid ""
"Remember that arguments are passed by assignment in Python. Since "
"assignment just creates references to objects, there's no alias between an "
"argument name in the caller and callee, and so no call-by-reference per se. "
"You can achieve the desired effect in a number of ways."
msgstr ""
#: ../../faq/programming.rst:510
msgid "By returning a tuple of the results::"
msgstr ""
#: ../../faq/programming.rst:521
msgid "This is almost always the clearest solution."
msgstr ""
#: ../../faq/programming.rst:523
msgid ""
"By using global variables. This isn't thread-safe, and is not recommended."
msgstr ""
#: ../../faq/programming.rst:525
msgid "By passing a mutable (changeable in-place) object::"
msgstr ""
#: ../../faq/programming.rst:536
msgid "By passing in a dictionary that gets mutated::"
msgstr ""
#: ../../faq/programming.rst:547
msgid "Or bundle up values in a class instance::"
msgstr ""
#: ../../faq/programming.rst:564
msgid "There's almost never a good reason to get this complicated."
msgstr ""
#: ../../faq/programming.rst:566
msgid "Your best choice is to return a tuple containing the multiple results."
msgstr ""
#: ../../faq/programming.rst:570
msgid "How do you make a higher order function in Python?"
msgstr ""
#: ../../faq/programming.rst:572
msgid ""
"You have two choices: you can use nested scopes or you can use callable "
"objects. For example, suppose you wanted to define ``linear(a,b)`` which "
"returns a function ``f(x)`` that computes the value ``a*x+b``. Using nested "
"scopes::"
msgstr ""
#: ../../faq/programming.rst:581
msgid "Or using a callable object::"
msgstr ""
#: ../../faq/programming.rst:591
msgid "In both cases, ::"
msgstr ""
#: ../../faq/programming.rst:595
msgid "gives a callable object where ``taxes(10e6) == 0.3 * 10e6 + 2``."
msgstr ""
#: ../../faq/programming.rst:597
msgid ""
"The callable object approach has the disadvantage that it is a bit slower "
"and results in slightly longer code. However, note that a collection of "
"callables can share their signature via inheritance::"
msgstr ""
#: ../../faq/programming.rst:606
msgid "Object can encapsulate state for several methods::"
msgstr ""
#: ../../faq/programming.rst:624
msgid ""
"Here ``inc()``, ``dec()`` and ``reset()`` act like functions which share the "
"same counting variable."
msgstr ""
#: ../../faq/programming.rst:629
msgid "How do I copy an object in Python?"
msgstr ""
#: ../../faq/programming.rst:631
msgid ""
"In general, try :func:`copy.copy` or :func:`copy.deepcopy` for the general "
"case. Not all objects can be copied, but most can."
msgstr ""
#: ../../faq/programming.rst:634
msgid ""
"Some objects can be copied more easily. Dictionaries have a :meth:`~dict."
"copy` method::"
msgstr ""
#: ../../faq/programming.rst:639
msgid "Sequences can be copied by slicing::"
msgstr ""
#: ../../faq/programming.rst:645
msgid "How can I find the methods or attributes of an object?"
msgstr ""
#: ../../faq/programming.rst:647
msgid ""
"For an instance x of a user-defined class, ``dir(x)`` returns an "
"alphabetized list of the names containing the instance attributes and "
"methods and attributes defined by its class."
msgstr ""
#: ../../faq/programming.rst:653
msgid "How can my code discover the name of an object?"
msgstr ""
#: ../../faq/programming.rst:655
msgid ""
"Generally speaking, it can't, because objects don't really have names. "
"Essentially, assignment always binds a name to a value; the same is true of "
"``def`` and ``class`` statements, but in that case the value is a callable. "
"Consider the following code::"
msgstr ""
#: ../../faq/programming.rst:671
msgid ""
"Arguably the class has a name: even though it is bound to two names and "
"invoked through the name B the created instance is still reported as an "
"instance of class A. However, it is impossible to say whether the "
"instance's name is a or b, since both names are bound to the same value."
msgstr ""
#: ../../faq/programming.rst:676
msgid ""
"Generally speaking it should not be necessary for your code to \"know the "
"names\" of particular values. Unless you are deliberately writing "
"introspective programs, this is usually an indication that a change of "
"approach might be beneficial."
msgstr ""
#: ../../faq/programming.rst:681
msgid ""
"In comp.lang.python, Fredrik Lundh once gave an excellent analogy in answer "
"to this question:"
msgstr ""
#: ../../faq/programming.rst:684
msgid ""
"The same way as you get the name of that cat you found on your porch: the "
"cat (object) itself cannot tell you its name, and it doesn't really care -- "
"so the only way to find out what it's called is to ask all your neighbours "
"(namespaces) if it's their cat (object)..."
msgstr ""
#: ../../faq/programming.rst:689
msgid ""
"....and don't be surprised if you'll find that it's known by many names, or "
"no name at all!"
msgstr ""
#: ../../faq/programming.rst:694
msgid "What's up with the comma operator's precedence?"
msgstr ""
#: ../../faq/programming.rst:696
msgid "Comma is not an operator in Python. Consider this session::"
msgstr ""
#: ../../faq/programming.rst:701
msgid ""
"Since the comma is not an operator, but a separator between expressions the "
"above is evaluated as if you had entered::"
msgstr ""
#: ../../faq/programming.rst:706
msgid "not::"
msgstr ""
#: ../../faq/programming.rst:710
msgid ""
"The same is true of the various assignment operators (``=``, ``+=`` etc). "
"They are not truly operators but syntactic delimiters in assignment "
"statements."
msgstr ""
#: ../../faq/programming.rst:715
msgid "Is there an equivalent of C's \"?:\" ternary operator?"
msgstr ""
#: ../../faq/programming.rst:717
msgid "Yes, there is. The syntax is as follows::"
msgstr ""
#: ../../faq/programming.rst:724
msgid ""
"Before this syntax was introduced in Python 2.5, a common idiom was to use "
"logical operators::"
msgstr ""
#: ../../faq/programming.rst:729
msgid ""
"However, this idiom is unsafe, as it can give wrong results when *on_true* "
"has a false boolean value. Therefore, it is always better to use the ``... "
"if ... else ...`` form."
msgstr ""
#: ../../faq/programming.rst:735
msgid "Is it possible to write obfuscated one-liners in Python?"
msgstr ""
#: ../../faq/programming.rst:737
msgid ""
"Yes. Usually this is done by nesting :keyword:`lambda` within :keyword:`!"
"lambda`. See the following three examples, slightly adapted from Ulf "
"Bartelt::"
msgstr ""
#: ../../faq/programming.rst:764
msgid "Don't try this at home, kids!"
msgstr ""
#: ../../faq/programming.rst:770
msgid "What does the slash(/) in the parameter list of a function mean?"
msgstr ""
#: ../../faq/programming.rst:772
msgid ""
"A slash in the argument list of a function denotes that the parameters prior "
"to it are positional-only. Positional-only parameters are the ones without "
"an externally usable name. Upon calling a function that accepts positional-"
"only parameters, arguments are mapped to parameters based solely on their "
"position. For example, :func:`divmod` is a function that accepts positional-"
"only parameters. Its documentation looks like this::"
msgstr ""
#: ../../faq/programming.rst:785
msgid ""
"The slash at the end of the parameter list means that both parameters are "
"positional-only. Thus, calling :func:`divmod` with keyword arguments would "
"lead to an error::"
msgstr ""
#: ../../faq/programming.rst:796
msgid "Numbers and strings"
msgstr ""
#: ../../faq/programming.rst:799
msgid "How do I specify hexadecimal and octal integers?"
msgstr ""
#: ../../faq/programming.rst:801
msgid ""
"To specify an octal digit, precede the octal value with a zero, and then a "
"lower or uppercase \"o\". For example, to set the variable \"a\" to the "
"octal value \"10\" (8 in decimal), type::"
msgstr ""
#: ../../faq/programming.rst:809
msgid ""
"Hexadecimal is just as easy. Simply precede the hexadecimal number with a "
"zero, and then a lower or uppercase \"x\". Hexadecimal digits can be "
"specified in lower or uppercase. For example, in the Python interpreter::"
msgstr ""
#: ../../faq/programming.rst:822
msgid "Why does -22 // 10 return -3?"
msgstr ""
#: ../../faq/programming.rst:824
msgid ""
"It's primarily driven by the desire that ``i % j`` have the same sign as "
"``j``. If you want that, and also want::"
msgstr ""
#: ../../faq/programming.rst:829
msgid ""
"then integer division has to return the floor. C also requires that "
"identity to hold, and then compilers that truncate ``i // j`` need to make "
"``i % j`` have the same sign as ``i``."
msgstr ""
#: ../../faq/programming.rst:833
msgid ""
"There are few real use cases for ``i % j`` when ``j`` is negative. When "
"``j`` is positive, there are many, and in virtually all of them it's more "
"useful for ``i % j`` to be ``>= 0``. If the clock says 10 now, what did it "
"say 200 hours ago? ``-190 % 12 == 2`` is useful; ``-190 % 12 == -10`` is a "
"bug waiting to bite."
msgstr ""
#: ../../faq/programming.rst:841
msgid "How do I get int literal attribute instead of SyntaxError?"
msgstr ""
#: ../../faq/programming.rst:843
msgid ""
"Trying to lookup an ``int`` literal attribute in the normal manner gives a "
"syntax error because the period is seen as a decimal point::"
msgstr ""
#: ../../faq/programming.rst:852
msgid ""
"The solution is to separate the literal from the period with either a space "
"or parentheses."
msgstr ""
#: ../../faq/programming.rst:862
msgid "How do I convert a string to a number?"
msgstr ""
#: ../../faq/programming.rst:864
msgid ""
"For integers, use the built-in :func:`int` type constructor, e.g. "
"``int('144') == 144``. Similarly, :func:`float` converts to floating-point, "
"e.g. ``float('144') == 144.0``."
msgstr ""
#: ../../faq/programming.rst:868
msgid ""
"By default, these interpret the number as decimal, so that ``int('0144') == "
"144`` holds true, and ``int('0x144')`` raises :exc:`ValueError`. "
"``int(string, base)`` takes the base to convert from as a second optional "
"argument, so ``int( '0x144', 16) == 324``. If the base is specified as 0, "
"the number is interpreted using Python's rules: a leading '0o' indicates "
"octal, and '0x' indicates a hex number."
msgstr ""
#: ../../faq/programming.rst:875
msgid ""
"Do not use the built-in function :func:`eval` if all you need is to convert "
"strings to numbers. :func:`eval` will be significantly slower and it "
"presents a security risk: someone could pass you a Python expression that "
"might have unwanted side effects. For example, someone could pass "
"``__import__('os').system(\"rm -rf $HOME\")`` which would erase your home "
"directory."
msgstr ""