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2908 lines (2402 loc) · 83.9 KB
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# SOME DESCRIPTIVE TITLE.
# Copyright (C) 2001 Python Software Foundation
# This file is distributed under the same license as the Python package.
# FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
#
# Translators:
# python-doc bot, 2025
# Vladimir, 2025
#
#, fuzzy
msgid ""
msgstr ""
"Project-Id-Version: Python 3.15\n"
"Report-Msgid-Bugs-To: \n"
"POT-Creation-Date: 2026-08-25 14:37+0000\n"
"PO-Revision-Date: 2025-09-16 00:00+0000\n"
"Last-Translator: Vladimir, 2025\n"
"Language-Team: Russian (https://app.transifex.com/python-doc/teams/5390/"
"ru/)\n"
"MIME-Version: 1.0\n"
"Content-Type: text/plain; charset=UTF-8\n"
"Content-Transfer-Encoding: 8bit\n"
"Language: ru\n"
"Plural-Forms: nplurals=4; plural=(n%10==1 && n%100!=11 ? 0 : n%10>=2 && "
"n%10<=4 && (n%100<12 || n%100>14) ? 1 : n%10==0 || (n%10>=5 && n%10<=9) || "
"(n%100>=11 && n%100<=14)? 2 : 3);\n"
msgid "Programming FAQ"
msgstr ""
msgid "Contents"
msgstr ""
msgid "General questions"
msgstr ""
msgid ""
"Is there a source code-level debugger with breakpoints and single-stepping?"
msgstr ""
msgid "Yes."
msgstr ""
msgid ""
"Several debuggers for Python are described below, and the built-in function :"
"func:`breakpoint` allows you to drop into any of them."
msgstr ""
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 ""
msgid ""
"The IDLE interactive development environment, which is part of the standard "
"Python distribution (normally available as :mod:`idlelib`), includes a "
"graphical debugger."
msgstr ""
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 ""
msgid ""
"`Eric <https://eric-ide.python-projects.org/>`_ is an IDE built on PyQt and "
"the Scintilla editing component."
msgstr ""
msgid ""
"`trepan3k <https://github.com/rocky/python3-trepan/>`_ is a gdb-like "
"debugger."
msgstr ""
msgid ""
"`Visual Studio Code <https://code.visualstudio.com/>`_ is an IDE with "
"debugging tools that integrates with version-control software."
msgstr ""
msgid ""
"There are a number of commercial Python IDEs that include graphical "
"debuggers. They include:"
msgstr ""
msgid "`Wing IDE <https://wingware.com/>`_"
msgstr ""
msgid "`PyCharm <https://www.jetbrains.com/pycharm/>`_"
msgstr ""
msgid "Are there tools to help find bugs or perform static analysis?"
msgstr ""
msgid ""
"`Ruff <https://docs.astral.sh/ruff/>`__, `Pylint <https://pylint.readthedocs."
"io/>`__ and `Pyflakes <https://github.com/PyCQA/pyflakes>`__ do basic "
"checking that will help you catch bugs sooner."
msgstr ""
msgid ""
"Static type checkers such as `mypy <https://mypy-lang.org/>`__, `ty <https://"
"docs.astral.sh/ty/>`__, `Pyrefly <https://pyrefly.org/>`__, and `pytype "
"<https://github.com/google/pytype>`__ can check type hints in Python source "
"code."
msgstr ""
msgid "How can I create a stand-alone binary from a Python script?"
msgstr ""
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 ""
msgid ""
"One is to use the freeze tool, which is included in the Python source tree "
"as :source:`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 ""
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 ""
msgid ""
"The following packages can help with the creation of console and GUI "
"executables:"
msgstr ""
msgid "`Nuitka <https://nuitka.net/>`_ (Cross-platform)"
msgstr ""
msgid "`PyInstaller <https://pyinstaller.org/>`_ (Cross-platform)"
msgstr ""
msgid ""
"`PyOxidizer <https://pyoxidizer.readthedocs.io/en/stable/>`_ (Cross-platform)"
msgstr ""
msgid ""
"`cx_Freeze <https://marcelotduarte.github.io/cx_Freeze/>`_ (Cross-platform)"
msgstr ""
msgid "`py2app <https://github.com/ronaldoussoren/py2app>`_ (macOS only)"
msgstr ""
msgid "`py2exe <https://www.py2exe.org/>`_ (Windows only)"
msgstr ""
msgid "Are there coding standards or a style guide for Python programs?"
msgstr ""
msgid ""
"Yes. The coding style required for standard library modules is documented "
"as :pep:`8`."
msgstr ""
msgid "Core language"
msgstr ""
msgid "Why am I getting an UnboundLocalError when the variable has a value?"
msgstr ""
msgid ""
"It can be a surprise to get the :exc:`UnboundLocalError` in previously "
"working code when it is modified by adding an assignment statement somewhere "
"in the body of a function."
msgstr ""
msgid "This code:"
msgstr ""
msgid "works, but this code:"
msgstr ""
msgid "results in an :exc:`!UnboundLocalError`:"
msgstr ""
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 ""
msgid ""
"In the example above you can access the outer scope variable by declaring it "
"global:"
msgstr ""
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 ""
msgid ""
"You can do a similar thing in a nested scope using the :keyword:`nonlocal` "
"keyword:"
msgstr ""
msgid "What are the rules for local and global variables in Python?"
msgstr ""
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 ""
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 ""
msgid ""
"Why do lambdas defined in a loop with different values all return the same "
"result?"
msgstr ""
msgid ""
"Assume you use a for loop to define a few different lambdas (or even plain "
"functions), for example::"
msgstr ""
msgid ""
">>> squares = []\n"
">>> for x in range(5):\n"
"... squares.append(lambda: x**2)"
msgstr ""
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 ""
msgid ""
">>> squares[2]()\n"
"16\n"
">>> squares[4]()\n"
"16"
msgstr ""
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``, that is ``16``. You can also verify this "
"by changing the value of ``x`` and see how the results of the lambdas "
"change::"
msgstr ""
msgid ""
">>> x = 8\n"
">>> squares[2]()\n"
"64"
msgstr ""
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 ""
msgid ""
">>> squares = []\n"
">>> for x in range(5):\n"
"... squares.append(lambda n=x: n**2)"
msgstr ""
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 ""
msgid ""
">>> squares[2]()\n"
"4\n"
">>> squares[4]()\n"
"16"
msgstr ""
msgid ""
"Note that this behaviour is not peculiar to lambdas, but applies to regular "
"functions too."
msgstr ""
msgid "How do I share global variables across modules?"
msgstr ""
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 ""
msgid "config.py::"
msgstr ""
msgid "x = 0 # Default value of the 'x' configuration setting"
msgstr ""
msgid "mod.py::"
msgstr ""
msgid ""
"import config\n"
"config.x = 1"
msgstr ""
msgid "main.py::"
msgstr ""
msgid ""
"import config\n"
"import mod\n"
"print(config.x)"
msgstr ""
msgid ""
"Note that using a module is also the basis for implementing the singleton "
"design pattern, for the same reason."
msgstr ""
msgid "What are the \"best practices\" for using import in a module?"
msgstr ""
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 ""
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 ""
msgid "It's good practice if you import modules in the following order:"
msgstr ""
msgid ""
"standard library modules -- such as :mod:`sys`, :mod:`os`, :mod:`argparse`, :"
"mod:`re`"
msgstr ""
msgid ""
"third-party library modules (anything installed in Python's site-packages "
"directory) -- such as :pypi:`dateutil`, :pypi:`requests`, :pypi:`tzdata`"
msgstr ""
msgid "locally developed modules"
msgstr ""
msgid ""
"It is sometimes necessary to move imports to a function or class to avoid "
"problems with circular imports. Gordon McMillan says:"
msgstr ""
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 ""
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 ""
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 ""
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 ""
msgid "Why are default values shared between objects?"
msgstr ""
msgid ""
"This type of bug commonly bites neophyte programmers. Consider this "
"function::"
msgstr ""
msgid ""
"def foo(mydict={}): # Danger: shared reference to one dict for all calls\n"
" ... compute something ...\n"
" mydict[key] = value\n"
" return mydict"
msgstr ""
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 ""
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 ""
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 ""
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 ""
msgid ""
"def foo(mydict={}):\n"
" ..."
msgstr ""
msgid "but::"
msgstr ""
msgid ""
"def foo(mydict=None):\n"
" if mydict is None:\n"
" mydict = {} # create a new dict for local namespace"
msgstr ""
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 ""
msgid ""
"# Callers can only provide two parameters and optionally pass _cache by "
"keyword\n"
"def expensive(arg1, arg2, *, _cache={}):\n"
" if (arg1, arg2) in _cache:\n"
" return _cache[(arg1, arg2)]\n"
"\n"
" # Calculate the value\n"
" result = ... expensive computation ...\n"
" _cache[(arg1, arg2)] = result # Store result in the cache\n"
" return result"
msgstr ""
msgid ""
"You could use a global variable containing a dictionary instead of the "
"default value; it's a matter of taste."
msgstr ""
msgid ""
"How can I pass optional or keyword parameters from one function to another?"
msgstr ""
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 ""
msgid ""
"def f(x, *args, **kwargs):\n"
" ...\n"
" kwargs['width'] = '14.3c'\n"
" ...\n"
" g(x, *args, **kwargs)"
msgstr ""
msgid "What is the difference between arguments and parameters?"
msgstr ""
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 ""
msgid ""
"def func(foo, bar=None, **kwargs):\n"
" pass"
msgstr ""
msgid ""
"*foo*, *bar* and *kwargs* are parameters of ``func``. However, when calling "
"``func``, for example::"
msgstr ""
msgid "func(42, bar=314, extra=somevar)"
msgstr ""
msgid "the values ``42``, ``314``, and ``somevar`` are arguments."
msgstr ""
msgid "Why did changing list 'y' also change list 'x'?"
msgstr ""
msgid "If you wrote code like::"
msgstr ""
msgid ""
">>> x = []\n"
">>> y = x\n"
">>> y.append(10)\n"
">>> y\n"
"[10]\n"
">>> x\n"
"[10]"
msgstr ""
msgid ""
"you might be wondering why appending an element to ``y`` changed ``x`` too."
msgstr ""
msgid "There are two factors that produce this result:"
msgstr ""
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 ""
msgid ""
"Lists are :term:`mutable`, which means that you can change their content."
msgstr ""
msgid ""
"After the call to :meth:`~sequence.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 ""
msgid "If we instead assign an immutable object to ``x``::"
msgstr ""
msgid ""
">>> x = 5 # ints are immutable\n"
">>> y = x\n"
">>> x = x + 1 # 5 can't be mutated, we are creating a new object here\n"
">>> x\n"
"6\n"
">>> y\n"
"5"
msgstr ""
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 ""
msgid ""
"Some operations (for example ``y.append(10)`` and ``y.sort()``) mutate the "
"object, whereas superficially similar operations (for example ``y = y + "
"[10]`` and :func:`sorted(y) <sorted>`) 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 ""
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 ""
msgid "In other words:"
msgstr ""
msgid ""
"If we have a mutable object (such as :class:`list`, :class:`dict`, :class:"
"`set`), we can use some specific operations to mutate it and all the "
"variables that refer to it will see the change."
msgstr ""
msgid ""
"If we have an immutable object (such as :class:`str`, :class:`int`, :class:"
"`tuple`), 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 ""
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 ""
msgid "How do I write a function with output parameters (call by reference)?"
msgstr ""
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 consequently no call-by-"
"reference. You can achieve the desired effect in a number of ways."
msgstr ""
msgid "By returning a tuple of the results::"
msgstr ""
msgid ""
">>> def func1(a, b):\n"
"... a = 'new-value' # a and b are local names\n"
"... b = b + 1 # assigned to new objects\n"
"... return a, b # return new values\n"
"...\n"
">>> x, y = 'old-value', 99\n"
">>> func1(x, y)\n"
"('new-value', 100)"
msgstr ""
msgid "This is almost always the clearest solution."
msgstr ""
msgid ""
"By using global variables. This isn't thread-safe, and is not recommended."
msgstr ""
msgid "By passing a mutable (changeable in-place) object::"
msgstr ""
msgid ""
">>> def func2(a):\n"
"... a[0] = 'new-value' # 'a' references a mutable list\n"
"... a[1] = a[1] + 1 # changes a shared object\n"
"...\n"
">>> args = ['old-value', 99]\n"
">>> func2(args)\n"
">>> args\n"
"['new-value', 100]"
msgstr ""
msgid "By passing in a dictionary that gets mutated::"
msgstr ""
msgid ""
">>> def func3(args):\n"
"... args['a'] = 'new-value' # args is a mutable dictionary\n"
"... args['b'] = args['b'] + 1 # change it in-place\n"
"...\n"
">>> args = {'a': 'old-value', 'b': 99}\n"
">>> func3(args)\n"
">>> args\n"
"{'a': 'new-value', 'b': 100}"
msgstr ""
msgid "Or bundle up values in a class instance::"
msgstr ""
msgid ""
">>> class Namespace:\n"
"... def __init__(self, /, **args):\n"
"... for key, value in args.items():\n"
"... setattr(self, key, value)\n"
"...\n"
">>> def func4(args):\n"
"... args.a = 'new-value' # args is a mutable Namespace\n"
"... args.b = args.b + 1 # change object in-place\n"
"...\n"
">>> args = Namespace(a='old-value', b=99)\n"
">>> func4(args)\n"
">>> vars(args)\n"
"{'a': 'new-value', 'b': 100}"
msgstr ""
msgid "There's almost never a good reason to get this complicated."
msgstr ""
msgid "Your best choice is to return a tuple containing the multiple results."
msgstr ""
msgid "How do you make a higher order function in Python?"
msgstr ""
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 ""
msgid ""
"def linear(a, b):\n"
" def result(x):\n"
" return a * x + b\n"
" return result"
msgstr ""
msgid "Or using a callable object::"
msgstr ""
msgid ""
"class linear:\n"
"\n"
" def __init__(self, a, b):\n"
" self.a, self.b = a, b\n"
"\n"
" def __call__(self, x):\n"
" return self.a * x + self.b"
msgstr ""
msgid "In both cases, ::"
msgstr ""
msgid "taxes = linear(0.3, 2)"
msgstr ""
msgid "gives a callable object where ``taxes(10e6) == 0.3 * 10e6 + 2``."
msgstr ""
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 ""
msgid ""
"class exponential(linear):\n"
" # __init__ inherited\n"
" def __call__(self, x):\n"
" return self.a * (x ** self.b)"
msgstr ""
msgid "Object can encapsulate state for several methods::"
msgstr ""
msgid ""
"class counter:\n"
"\n"
" value = 0\n"
"\n"
" def set(self, x):\n"
" self.value = x\n"
"\n"
" def up(self):\n"
" self.value = self.value + 1\n"
"\n"
" def down(self):\n"
" self.value = self.value - 1\n"
"\n"
"count = counter()\n"
"inc, dec, reset = count.up, count.down, count.set"
msgstr ""
msgid ""
"Here ``inc()``, ``dec()`` and ``reset()`` act like functions which share the "
"same counting variable."
msgstr ""
msgid "How do I copy an object in Python?"
msgstr ""
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 ""
msgid ""
"Some objects can be copied more easily. Dictionaries have a :meth:`~dict."
"copy` method::"
msgstr ""
msgid "newdict = olddict.copy()"
msgstr ""
msgid "Sequences can be copied by slicing::"
msgstr ""
msgid "new_l = l[:]"
msgstr ""
msgid "How can I find the methods or attributes of an object?"
msgstr ""
msgid ""
"For an instance ``x`` of a user-defined class, :func:`dir(x) <dir>` returns "
"an alphabetized list of the names containing the instance attributes and "
"methods and attributes defined by its class."
msgstr ""
msgid "How can my code discover the name of an object?"
msgstr ""
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 ""
msgid ""
">>> class A:\n"
"... pass\n"
"...\n"
">>> B = A\n"
">>> a = B()\n"
">>> b = a\n"
">>> print(b)\n"
"<__main__.A object at 0x16D07CC>\n"
">>> print(a)\n"
"<__main__.A object at 0x16D07CC>"
msgstr ""
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 ""
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 ""
msgid ""
"In comp.lang.python, Fredrik Lundh once gave an excellent analogy in answer "
"to this question:"
msgstr ""
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 ""
msgid ""
"....and don't be surprised if you'll find that it's known by many names, or "
"no name at all!"
msgstr ""
msgid "What's up with the comma operator's precedence?"
msgstr ""
msgid "Comma is not an operator in Python. Consider this session::"
msgstr ""
msgid ""
">>> \"a\" in \"b\", \"a\"\n"
"(False, 'a')"
msgstr ""
msgid ""
"Since the comma is not an operator, but a separator between expressions the "
"above is evaluated as if you had entered::"
msgstr ""
msgid "(\"a\" in \"b\"), \"a\""
msgstr ""
msgid "not::"
msgstr ""
msgid "\"a\" in (\"b\", \"a\")"
msgstr ""
msgid ""
"The same is true of the various assignment operators (``=``, ``+=``, and so "
"on). They are not truly operators but syntactic delimiters in assignment "
"statements."
msgstr ""
msgid "Is there an equivalent of C's \"?:\" ternary operator?"
msgstr ""
msgid "Yes, there is. The syntax is as follows::"
msgstr ""
msgid ""
"[on_true] if [expression] else [on_false]\n"
"\n"
"x, y = 50, 25\n"
"small = x if x < y else y"
msgstr ""
msgid ""
"Before this syntax was introduced in Python 2.5, a common idiom was to use "
"logical operators::"
msgstr ""
msgid "[expression] and [on_true] or [on_false]"
msgstr ""
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 ""
msgid "Is it possible to write obfuscated one-liners in Python?"
msgstr ""
msgid ""
"Yes. Usually this is done by nesting :keyword:`lambda` within :keyword:`!"
"lambda`. See the following three examples, slightly adapted from Ulf "
"Bartelt::"
msgstr ""
msgid ""
"from functools import reduce\n"
"\n"
"# Primes < 1000\n"
"print(list(filter(None,map(lambda y:y*reduce(lambda x,y:x*y!=0,\n"
"map(lambda x,y=y:y%x,range(2,int(pow(y,0.5)+1))),1),range(2,1000)))))\n"
"\n"
"# First 10 Fibonacci numbers\n"
"print(list(map(lambda x,f=lambda x,f:(f(x-1,f)+f(x-2,f)) if x>1 else 1:\n"
"f(x,f), range(10))))\n"
"\n"
"# Mandelbrot set\n"
"print((lambda Ru,Ro,Iu,Io,IM,Sx,Sy:reduce(lambda x,y:x+'\\n'+y,map(lambda "
"y,\n"
"Iu=Iu,Io=Io,Ru=Ru,Ro=Ro,Sy=Sy,L=lambda yc,Iu=Iu,Io=Io,Ru=Ru,Ro=Ro,i=IM,\n"
"Sx=Sx,Sy=Sy:reduce(lambda x,y:x+y,map(lambda x,xc=Ru,yc=yc,Ru=Ru,Ro=Ro,\n"
"i=i,Sx=Sx,F=lambda xc,yc,x,y,k,f=lambda xc,yc,x,y,k,f:(k<=0)or (x*x+y*y\n"
">=4.0) or 1+f(xc,yc,x*x-y*y+xc,2.0*x*y+yc,k-1,f):f(xc,yc,x,y,k,f):chr(\n"
"64+F(Ru+x*(Ro-Ru)/Sx,yc,0,0,i)),range(Sx))):L(Iu+y*(Io-Iu)/Sy),range(Sy\n"
"))))(-2.1, 0.7, -1.2, 1.2, 30, 80, 24))\n"
"# \\___ ___/ \\___ ___/ | | |__ lines on screen\n"
"# V V | |______ columns on screen\n"
"# | | |__________ maximum of \"iterations\"\n"