# SOME DESCRIPTIVE TITLE. # Copyright (C) 2001-2019, Python Software Foundation # This file is distributed under the same license as the Python package. # FIRST AUTHOR , YEAR. # # Translators: # oon arfiandwi , 2019 # #, fuzzy msgid "" msgstr "" "Project-Id-Version: Python 3.8\n" "Report-Msgid-Bugs-To: \n" "POT-Creation-Date: 2019-09-01 14:24+0000\n" "PO-Revision-Date: 2017-02-16 23:39+0000\n" "Last-Translator: oon arfiandwi , 2019\n" "Language-Team: Indonesian (https://www.transifex.com/python-doc/teams/5390/id/)\n" "MIME-Version: 1.0\n" "Content-Type: text/plain; charset=UTF-8\n" "Content-Transfer-Encoding: 8bit\n" "Language: id\n" "Plural-Forms: nplurals=1; plural=0;\n" #: ../../tutorial/classes.rst:5 msgid "Classes" msgstr "" #: ../../tutorial/classes.rst:7 msgid "" "Classes provide a means of bundling data and functionality together. " "Creating a new class creates a new *type* of object, allowing new " "*instances* of that type to be made. Each class instance can have " "attributes attached to it for maintaining its state. Class instances can " "also have methods (defined by its class) for modifying its state." msgstr "" #: ../../tutorial/classes.rst:13 msgid "" "Compared with other programming languages, Python's class mechanism adds " "classes with a minimum of new syntax and semantics. It is a mixture of the " "class mechanisms found in C++ and Modula-3. Python classes provide all the " "standard features of Object Oriented Programming: the class inheritance " "mechanism allows multiple base classes, a derived class can override any " "methods of its base class or classes, and a method can call the method of a " "base class with the same name. Objects can contain arbitrary amounts and " "kinds of data. As is true for modules, classes partake of the dynamic " "nature of Python: they are created at runtime, and can be modified further " "after creation." msgstr "" #: ../../tutorial/classes.rst:23 msgid "" "In C++ terminology, normally class members (including the data members) are " "*public* (except see below :ref:`tut-private`), and all member functions are" " *virtual*. As in Modula-3, there are no shorthands for referencing the " "object's members from its methods: the method function is declared with an " "explicit first argument representing the object, which is provided " "implicitly by the call. As in Smalltalk, classes themselves are objects. " "This provides semantics for importing and renaming. Unlike C++ and " "Modula-3, built-in types can be used as base classes for extension by the " "user. Also, like in C++, most built-in operators with special syntax " "(arithmetic operators, subscripting etc.) can be redefined for class " "instances." msgstr "" #: ../../tutorial/classes.rst:34 msgid "" "(Lacking universally accepted terminology to talk about classes, I will make" " occasional use of Smalltalk and C++ terms. I would use Modula-3 terms, " "since its object-oriented semantics are closer to those of Python than C++, " "but I expect that few readers have heard of it.)" msgstr "" #: ../../tutorial/classes.rst:43 msgid "A Word About Names and Objects" msgstr "" #: ../../tutorial/classes.rst:45 msgid "" "Objects have individuality, and multiple names (in multiple scopes) can be " "bound to the same object. This is known as aliasing in other languages. " "This is usually not appreciated on a first glance at Python, and can be " "safely ignored when dealing with immutable basic types (numbers, strings, " "tuples). However, aliasing has a possibly surprising effect on the " "semantics of Python code involving mutable objects such as lists, " "dictionaries, and most other types. This is usually used to the benefit of " "the program, since aliases behave like pointers in some respects. For " "example, passing an object is cheap since only a pointer is passed by the " "implementation; and if a function modifies an object passed as an argument, " "the caller will see the change --- this eliminates the need for two " "different argument passing mechanisms as in Pascal." msgstr "" #: ../../tutorial/classes.rst:61 msgid "Python Scopes and Namespaces" msgstr "" #: ../../tutorial/classes.rst:63 msgid "" "Before introducing classes, I first have to tell you something about " "Python's scope rules. Class definitions play some neat tricks with " "namespaces, and you need to know how scopes and namespaces work to fully " "understand what's going on. Incidentally, knowledge about this subject is " "useful for any advanced Python programmer." msgstr "" #: ../../tutorial/classes.rst:69 msgid "Let's begin with some definitions." msgstr "" #: ../../tutorial/classes.rst:71 msgid "" "A *namespace* is a mapping from names to objects. Most namespaces are " "currently implemented as Python dictionaries, but that's normally not " "noticeable in any way (except for performance), and it may change in the " "future. Examples of namespaces are: the set of built-in names (containing " "functions such as :func:`abs`, and built-in exception names); the global " "names in a module; and the local names in a function invocation. In a sense" " the set of attributes of an object also form a namespace. The important " "thing to know about namespaces is that there is absolutely no relation " "between names in different namespaces; for instance, two different modules " "may both define a function ``maximize`` without confusion --- users of the " "modules must prefix it with the module name." msgstr "" #: ../../tutorial/classes.rst:82 msgid "" "By the way, I use the word *attribute* for any name following a dot --- for " "example, in the expression ``z.real``, ``real`` is an attribute of the " "object ``z``. Strictly speaking, references to names in modules are " "attribute references: in the expression ``modname.funcname``, ``modname`` is" " a module object and ``funcname`` is an attribute of it. In this case there" " happens to be a straightforward mapping between the module's attributes and" " the global names defined in the module: they share the same namespace! " "[#]_" msgstr "" #: ../../tutorial/classes.rst:90 msgid "" "Attributes may be read-only or writable. In the latter case, assignment to " "attributes is possible. Module attributes are writable: you can write " "``modname.the_answer = 42``. Writable attributes may also be deleted with " "the :keyword:`del` statement. For example, ``del modname.the_answer`` will " "remove the attribute :attr:`the_answer` from the object named by " "``modname``." msgstr "" #: ../../tutorial/classes.rst:96 msgid "" "Namespaces are created at different moments and have different lifetimes. " "The namespace containing the built-in names is created when the Python " "interpreter starts up, and is never deleted. The global namespace for a " "module is created when the module definition is read in; normally, module " "namespaces also last until the interpreter quits. The statements executed " "by the top-level invocation of the interpreter, either read from a script " "file or interactively, are considered part of a module called " ":mod:`__main__`, so they have their own global namespace. (The built-in " "names actually also live in a module; this is called :mod:`builtins`.)" msgstr "" #: ../../tutorial/classes.rst:106 msgid "" "The local namespace for a function is created when the function is called, " "and deleted when the function returns or raises an exception that is not " "handled within the function. (Actually, forgetting would be a better way to" " describe what actually happens.) Of course, recursive invocations each " "have their own local namespace." msgstr "" #: ../../tutorial/classes.rst:112 msgid "" "A *scope* is a textual region of a Python program where a namespace is " "directly accessible. \"Directly accessible\" here means that an unqualified" " reference to a name attempts to find the name in the namespace." msgstr "" #: ../../tutorial/classes.rst:116 msgid "" "Although scopes are determined statically, they are used dynamically. At any" " time during execution, there are at least three nested scopes whose " "namespaces are directly accessible:" msgstr "" #: ../../tutorial/classes.rst:120 msgid "the innermost scope, which is searched first, contains the local names" msgstr "" #: ../../tutorial/classes.rst:121 msgid "" "the scopes of any enclosing functions, which are searched starting with the " "nearest enclosing scope, contains non-local, but also non-global names" msgstr "" #: ../../tutorial/classes.rst:123 msgid "the next-to-last scope contains the current module's global names" msgstr "" #: ../../tutorial/classes.rst:124 msgid "" "the outermost scope (searched last) is the namespace containing built-in " "names" msgstr "" #: ../../tutorial/classes.rst:126 msgid "" "If a name is declared global, then all references and assignments go " "directly to the middle scope containing the module's global names. To " "rebind variables found outside of the innermost scope, the " ":keyword:`nonlocal` statement can be used; if not declared nonlocal, those " "variables are read-only (an attempt to write to such a variable will simply " "create a *new* local variable in the innermost scope, leaving the " "identically named outer variable unchanged)." msgstr "" #: ../../tutorial/classes.rst:133 msgid "" "Usually, the local scope references the local names of the (textually) " "current function. Outside functions, the local scope references the same " "namespace as the global scope: the module's namespace. Class definitions " "place yet another namespace in the local scope." msgstr "" #: ../../tutorial/classes.rst:138 msgid "" "It is important to realize that scopes are determined textually: the global " "scope of a function defined in a module is that module's namespace, no " "matter from where or by what alias the function is called. On the other " "hand, the actual search for names is done dynamically, at run time --- " "however, the language definition is evolving towards static name resolution," " at \"compile\" time, so don't rely on dynamic name resolution! (In fact, " "local variables are already determined statically.)" msgstr "" #: ../../tutorial/classes.rst:146 msgid "" "A special quirk of Python is that -- if no :keyword:`global` statement is in" " effect -- assignments to names always go into the innermost scope. " "Assignments do not copy data --- they just bind names to objects. The same " "is true for deletions: the statement ``del x`` removes the binding of ``x`` " "from the namespace referenced by the local scope. In fact, all operations " "that introduce new names use the local scope: in particular, " ":keyword:`import` statements and function definitions bind the module or " "function name in the local scope." msgstr "" #: ../../tutorial/classes.rst:154 msgid "" "The :keyword:`global` statement can be used to indicate that particular " "variables live in the global scope and should be rebound there; the " ":keyword:`nonlocal` statement indicates that particular variables live in an" " enclosing scope and should be rebound there." msgstr "" #: ../../tutorial/classes.rst:162 msgid "Scopes and Namespaces Example" msgstr "" #: ../../tutorial/classes.rst:164 msgid "" "This is an example demonstrating how to reference the different scopes and " "namespaces, and how :keyword:`global` and :keyword:`nonlocal` affect " "variable binding::" msgstr "" #: ../../tutorial/classes.rst:191 msgid "The output of the example code is:" msgstr "" #: ../../tutorial/classes.rst:200 msgid "" "Note how the *local* assignment (which is default) didn't change " "*scope_test*\\'s binding of *spam*. The :keyword:`nonlocal` assignment " "changed *scope_test*\\'s binding of *spam*, and the :keyword:`global` " "assignment changed the module-level binding." msgstr "" #: ../../tutorial/classes.rst:205 msgid "" "You can also see that there was no previous binding for *spam* before the " ":keyword:`global` assignment." msgstr "" #: ../../tutorial/classes.rst:212 msgid "A First Look at Classes" msgstr "" #: ../../tutorial/classes.rst:214 msgid "" "Classes introduce a little bit of new syntax, three new object types, and " "some new semantics." msgstr "" #: ../../tutorial/classes.rst:221 msgid "Class Definition Syntax" msgstr "" #: ../../tutorial/classes.rst:223 msgid "The simplest form of class definition looks like this::" msgstr "" #: ../../tutorial/classes.rst:232 msgid "" "Class definitions, like function definitions (:keyword:`def` statements) " "must be executed before they have any effect. (You could conceivably place " "a class definition in a branch of an :keyword:`if` statement, or inside a " "function.)" msgstr "" #: ../../tutorial/classes.rst:236 msgid "" "In practice, the statements inside a class definition will usually be " "function definitions, but other statements are allowed, and sometimes useful" " --- we'll come back to this later. The function definitions inside a class" " normally have a peculiar form of argument list, dictated by the calling " "conventions for methods --- again, this is explained later." msgstr "" #: ../../tutorial/classes.rst:242 msgid "" "When a class definition is entered, a new namespace is created, and used as " "the local scope --- thus, all assignments to local variables go into this " "new namespace. In particular, function definitions bind the name of the new" " function here." msgstr "" #: ../../tutorial/classes.rst:247 msgid "" "When a class definition is left normally (via the end), a *class object* is " "created. This is basically a wrapper around the contents of the namespace " "created by the class definition; we'll learn more about class objects in the" " next section. The original local scope (the one in effect just before the " "class definition was entered) is reinstated, and the class object is bound " "here to the class name given in the class definition header " "(:class:`ClassName` in the example)." msgstr "" #: ../../tutorial/classes.rst:259 msgid "Class Objects" msgstr "" #: ../../tutorial/classes.rst:261 msgid "" "Class objects support two kinds of operations: attribute references and " "instantiation." msgstr "" #: ../../tutorial/classes.rst:264 msgid "" "*Attribute references* use the standard syntax used for all attribute " "references in Python: ``obj.name``. Valid attribute names are all the names" " that were in the class's namespace when the class object was created. So, " "if the class definition looked like this::" msgstr "" #: ../../tutorial/classes.rst:276 msgid "" "then ``MyClass.i`` and ``MyClass.f`` are valid attribute references, " "returning an integer and a function object, respectively. Class attributes " "can also be assigned to, so you can change the value of ``MyClass.i`` by " "assignment. :attr:`__doc__` is also a valid attribute, returning the " "docstring belonging to the class: ``\"A simple example class\"``." msgstr "" #: ../../tutorial/classes.rst:282 msgid "" "Class *instantiation* uses function notation. Just pretend that the class " "object is a parameterless function that returns a new instance of the class." " For example (assuming the above class)::" msgstr "" #: ../../tutorial/classes.rst:288 msgid "" "creates a new *instance* of the class and assigns this object to the local " "variable ``x``." msgstr "" #: ../../tutorial/classes.rst:291 msgid "" "The instantiation operation (\"calling\" a class object) creates an empty " "object. Many classes like to create objects with instances customized to a " "specific initial state. Therefore a class may define a special method named " ":meth:`__init__`, like this::" msgstr "" #: ../../tutorial/classes.rst:299 msgid "" "When a class defines an :meth:`__init__` method, class instantiation " "automatically invokes :meth:`__init__` for the newly-created class instance." " So in this example, a new, initialized instance can be obtained by::" msgstr "" #: ../../tutorial/classes.rst:305 msgid "" "Of course, the :meth:`__init__` method may have arguments for greater " "flexibility. In that case, arguments given to the class instantiation " "operator are passed on to :meth:`__init__`. For example, ::" msgstr "" #: ../../tutorial/classes.rst:322 msgid "Instance Objects" msgstr "" #: ../../tutorial/classes.rst:324 msgid "" "Now what can we do with instance objects? The only operations understood by" " instance objects are attribute references. There are two kinds of valid " "attribute names, data attributes and methods." msgstr "" #: ../../tutorial/classes.rst:328 msgid "" "*data attributes* correspond to \"instance variables\" in Smalltalk, and to " "\"data members\" in C++. Data attributes need not be declared; like local " "variables, they spring into existence when they are first assigned to. For " "example, if ``x`` is the instance of :class:`MyClass` created above, the " "following piece of code will print the value ``16``, without leaving a " "trace::" msgstr "" #: ../../tutorial/classes.rst:340 msgid "" "The other kind of instance attribute reference is a *method*. A method is a " "function that \"belongs to\" an object. (In Python, the term method is not " "unique to class instances: other object types can have methods as well. For" " example, list objects have methods called append, insert, remove, sort, and" " so on. However, in the following discussion, we'll use the term method " "exclusively to mean methods of class instance objects, unless explicitly " "stated otherwise.)" msgstr "" #: ../../tutorial/classes.rst:349 msgid "" "Valid method names of an instance object depend on its class. By " "definition, all attributes of a class that are function objects define " "corresponding methods of its instances. So in our example, ``x.f`` is a " "valid method reference, since ``MyClass.f`` is a function, but ``x.i`` is " "not, since ``MyClass.i`` is not. But ``x.f`` is not the same thing as " "``MyClass.f`` --- it is a *method object*, not a function object." msgstr "" #: ../../tutorial/classes.rst:360 msgid "Method Objects" msgstr "" #: ../../tutorial/classes.rst:362 msgid "Usually, a method is called right after it is bound::" msgstr "" #: ../../tutorial/classes.rst:366 msgid "" "In the :class:`MyClass` example, this will return the string ``'hello " "world'``. However, it is not necessary to call a method right away: ``x.f`` " "is a method object, and can be stored away and called at a later time. For " "example::" msgstr "" #: ../../tutorial/classes.rst:374 msgid "will continue to print ``hello world`` until the end of time." msgstr "" #: ../../tutorial/classes.rst:376 msgid "" "What exactly happens when a method is called? You may have noticed that " "``x.f()`` was called without an argument above, even though the function " "definition for :meth:`f` specified an argument. What happened to the " "argument? Surely Python raises an exception when a function that requires an" " argument is called without any --- even if the argument isn't actually " "used..." msgstr "" #: ../../tutorial/classes.rst:382 msgid "" "Actually, you may have guessed the answer: the special thing about methods " "is that the instance object is passed as the first argument of the function." " In our example, the call ``x.f()`` is exactly equivalent to " "``MyClass.f(x)``. In general, calling a method with a list of *n* arguments" " is equivalent to calling the corresponding function with an argument list " "that is created by inserting the method's instance object before the first " "argument." msgstr "" #: ../../tutorial/classes.rst:389 msgid "" "If you still don't understand how methods work, a look at the implementation" " can perhaps clarify matters. When a non-data attribute of an instance is " "referenced, the instance's class is searched. If the name denotes a valid " "class attribute that is a function object, a method object is created by " "packing (pointers to) the instance object and the function object just found" " together in an abstract object: this is the method object. When the method" " object is called with an argument list, a new argument list is constructed " "from the instance object and the argument list, and the function object is " "called with this new argument list." msgstr "" #: ../../tutorial/classes.rst:403 msgid "Class and Instance Variables" msgstr "" #: ../../tutorial/classes.rst:405 msgid "" "Generally speaking, instance variables are for data unique to each instance " "and class variables are for attributes and methods shared by all instances " "of the class::" msgstr "" #: ../../tutorial/classes.rst:427 msgid "" "As discussed in :ref:`tut-object`, shared data can have possibly surprising " "effects with involving :term:`mutable` objects such as lists and " "dictionaries. For example, the *tricks* list in the following code should " "not be used as a class variable because just a single list would be shared " "by all *Dog* instances::" msgstr "" #: ../../tutorial/classes.rst:450 msgid "Correct design of the class should use an instance variable instead::" msgstr "" #: ../../tutorial/classes.rst:474 msgid "Random Remarks" msgstr "" #: ../../tutorial/classes.rst:478 msgid "" "If the same attribute name occurs in both an instance and in a class, then " "attribute lookup prioritizes the instance::" msgstr "" #: ../../tutorial/classes.rst:493 msgid "" "Data attributes may be referenced by methods as well as by ordinary users " "(\"clients\") of an object. In other words, classes are not usable to " "implement pure abstract data types. In fact, nothing in Python makes it " "possible to enforce data hiding --- it is all based upon convention. (On " "the other hand, the Python implementation, written in C, can completely hide" " implementation details and control access to an object if necessary; this " "can be used by extensions to Python written in C.)" msgstr "" #: ../../tutorial/classes.rst:501 msgid "" "Clients should use data attributes with care --- clients may mess up " "invariants maintained by the methods by stamping on their data attributes. " "Note that clients may add data attributes of their own to an instance object" " without affecting the validity of the methods, as long as name conflicts " "are avoided --- again, a naming convention can save a lot of headaches here." msgstr "" #: ../../tutorial/classes.rst:507 msgid "" "There is no shorthand for referencing data attributes (or other methods!) " "from within methods. I find that this actually increases the readability of" " methods: there is no chance of confusing local variables and instance " "variables when glancing through a method." msgstr "" #: ../../tutorial/classes.rst:512 msgid "" "Often, the first argument of a method is called ``self``. This is nothing " "more than a convention: the name ``self`` has absolutely no special meaning " "to Python. Note, however, that by not following the convention your code " "may be less readable to other Python programmers, and it is also conceivable" " that a *class browser* program might be written that relies upon such a " "convention." msgstr "" #: ../../tutorial/classes.rst:518 msgid "" "Any function object that is a class attribute defines a method for instances" " of that class. It is not necessary that the function definition is " "textually enclosed in the class definition: assigning a function object to a" " local variable in the class is also ok. For example::" msgstr "" #: ../../tutorial/classes.rst:535 msgid "" "Now ``f``, ``g`` and ``h`` are all attributes of class :class:`C` that refer" " to function objects, and consequently they are all methods of instances of " ":class:`C` --- ``h`` being exactly equivalent to ``g``. Note that this " "practice usually only serves to confuse the reader of a program." msgstr "" #: ../../tutorial/classes.rst:540 msgid "" "Methods may call other methods by using method attributes of the ``self`` " "argument::" msgstr "" #: ../../tutorial/classes.rst:554 msgid "" "Methods may reference global names in the same way as ordinary functions. " "The global scope associated with a method is the module containing its " "definition. (A class is never used as a global scope.) While one rarely " "encounters a good reason for using global data in a method, there are many " "legitimate uses of the global scope: for one thing, functions and modules " "imported into the global scope can be used by methods, as well as functions " "and classes defined in it. Usually, the class containing the method is " "itself defined in this global scope, and in the next section we'll find some" " good reasons why a method would want to reference its own class." msgstr "" #: ../../tutorial/classes.rst:564 msgid "" "Each value is an object, and therefore has a *class* (also called its " "*type*). It is stored as ``object.__class__``." msgstr "" #: ../../tutorial/classes.rst:571 msgid "Inheritance" msgstr "" #: ../../tutorial/classes.rst:573 msgid "" "Of course, a language feature would not be worthy of the name \"class\" " "without supporting inheritance. The syntax for a derived class definition " "looks like this::" msgstr "" #: ../../tutorial/classes.rst:584 msgid "" "The name :class:`BaseClassName` must be defined in a scope containing the " "derived class definition. In place of a base class name, other arbitrary " "expressions are also allowed. This can be useful, for example, when the " "base class is defined in another module::" msgstr "" #: ../../tutorial/classes.rst:591 msgid "" "Execution of a derived class definition proceeds the same as for a base " "class. When the class object is constructed, the base class is remembered. " "This is used for resolving attribute references: if a requested attribute is" " not found in the class, the search proceeds to look in the base class. " "This rule is applied recursively if the base class itself is derived from " "some other class." msgstr "" #: ../../tutorial/classes.rst:597 msgid "" "There's nothing special about instantiation of derived classes: " "``DerivedClassName()`` creates a new instance of the class. Method " "references are resolved as follows: the corresponding class attribute is " "searched, descending down the chain of base classes if necessary, and the " "method reference is valid if this yields a function object." msgstr "" #: ../../tutorial/classes.rst:603 msgid "" "Derived classes may override methods of their base classes. Because methods" " have no special privileges when calling other methods of the same object, a" " method of a base class that calls another method defined in the same base " "class may end up calling a method of a derived class that overrides it. " "(For C++ programmers: all methods in Python are effectively ``virtual``.)" msgstr "" #: ../../tutorial/classes.rst:609 msgid "" "An overriding method in a derived class may in fact want to extend rather " "than simply replace the base class method of the same name. There is a " "simple way to call the base class method directly: just call " "``BaseClassName.methodname(self, arguments)``. This is occasionally useful " "to clients as well. (Note that this only works if the base class is " "accessible as ``BaseClassName`` in the global scope.)" msgstr "" #: ../../tutorial/classes.rst:616 msgid "Python has two built-in functions that work with inheritance:" msgstr "" #: ../../tutorial/classes.rst:618 msgid "" "Use :func:`isinstance` to check an instance's type: ``isinstance(obj, int)``" " will be ``True`` only if ``obj.__class__`` is :class:`int` or some class " "derived from :class:`int`." msgstr "" #: ../../tutorial/classes.rst:622 msgid "" "Use :func:`issubclass` to check class inheritance: ``issubclass(bool, int)``" " is ``True`` since :class:`bool` is a subclass of :class:`int`. However, " "``issubclass(float, int)`` is ``False`` since :class:`float` is not a " "subclass of :class:`int`." msgstr "" #: ../../tutorial/classes.rst:632 msgid "Multiple Inheritance" msgstr "" #: ../../tutorial/classes.rst:634 msgid "" "Python supports a form of multiple inheritance as well. A class definition " "with multiple base classes looks like this::" msgstr "" #: ../../tutorial/classes.rst:644 msgid "" "For most purposes, in the simplest cases, you can think of the search for " "attributes inherited from a parent class as depth-first, left-to-right, not " "searching twice in the same class where there is an overlap in the " "hierarchy. Thus, if an attribute is not found in :class:`DerivedClassName`, " "it is searched for in :class:`Base1`, then (recursively) in the base classes" " of :class:`Base1`, and if it was not found there, it was searched for in " ":class:`Base2`, and so on." msgstr "" #: ../../tutorial/classes.rst:651 msgid "" "In fact, it is slightly more complex than that; the method resolution order " "changes dynamically to support cooperative calls to :func:`super`. This " "approach is known in some other multiple-inheritance languages as call-next-" "method and is more powerful than the super call found in single-inheritance " "languages." msgstr "" #: ../../tutorial/classes.rst:657 msgid "" "Dynamic ordering is necessary because all cases of multiple inheritance " "exhibit one or more diamond relationships (where at least one of the parent " "classes can be accessed through multiple paths from the bottommost class). " "For example, all classes inherit from :class:`object`, so any case of " "multiple inheritance provides more than one path to reach :class:`object`. " "To keep the base classes from being accessed more than once, the dynamic " "algorithm linearizes the search order in a way that preserves the left-to-" "right ordering specified in each class, that calls each parent only once, " "and that is monotonic (meaning that a class can be subclassed without " "affecting the precedence order of its parents). Taken together, these " "properties make it possible to design reliable and extensible classes with " "multiple inheritance. For more detail, see " "https://www.python.org/download/releases/2.3/mro/." msgstr "" #: ../../tutorial/classes.rst:674 msgid "Private Variables" msgstr "" #: ../../tutorial/classes.rst:676 msgid "" "\"Private\" instance variables that cannot be accessed except from inside an" " object don't exist in Python. However, there is a convention that is " "followed by most Python code: a name prefixed with an underscore (e.g. " "``_spam``) should be treated as a non-public part of the API (whether it is " "a function, a method or a data member). It should be considered an " "implementation detail and subject to change without notice." msgstr "" #: ../../tutorial/classes.rst:686 msgid "" "Since there is a valid use-case for class-private members (namely to avoid " "name clashes of names with names defined by subclasses), there is limited " "support for such a mechanism, called :dfn:`name mangling`. Any identifier " "of the form ``__spam`` (at least two leading underscores, at most one " "trailing underscore) is textually replaced with ``_classname__spam``, where " "``classname`` is the current class name with leading underscore(s) stripped." " This mangling is done without regard to the syntactic position of the " "identifier, as long as it occurs within the definition of a class." msgstr "" #: ../../tutorial/classes.rst:695 msgid "" "Name mangling is helpful for letting subclasses override methods without " "breaking intraclass method calls. For example::" msgstr "" #: ../../tutorial/classes.rst:717 msgid "" "The above example would work even if ``MappingSubclass`` were to introduce a" " ``__update`` identifier since it is replaced with ``_Mapping__update`` in " "the ``Mapping`` class and ``_MappingSubclass__update`` in the " "``MappingSubclass`` class respectively." msgstr "" #: ../../tutorial/classes.rst:722 msgid "" "Note that the mangling rules are designed mostly to avoid accidents; it " "still is possible to access or modify a variable that is considered private." " This can even be useful in special circumstances, such as in the debugger." msgstr "" #: ../../tutorial/classes.rst:726 msgid "" "Notice that code passed to ``exec()`` or ``eval()`` does not consider the " "classname of the invoking class to be the current class; this is similar to " "the effect of the ``global`` statement, the effect of which is likewise " "restricted to code that is byte-compiled together. The same restriction " "applies to ``getattr()``, ``setattr()`` and ``delattr()``, as well as when " "referencing ``__dict__`` directly." msgstr "" #: ../../tutorial/classes.rst:737 msgid "Odds and Ends" msgstr "" #: ../../tutorial/classes.rst:739 msgid "" "Sometimes it is useful to have a data type similar to the Pascal \"record\" " "or C \"struct\", bundling together a few named data items. An empty class " "definition will do nicely::" msgstr "" #: ../../tutorial/classes.rst:753 msgid "" "A piece of Python code that expects a particular abstract data type can " "often be passed a class that emulates the methods of that data type instead." " For instance, if you have a function that formats some data from a file " "object, you can define a class with methods :meth:`read` and " ":meth:`!readline` that get the data from a string buffer instead, and pass " "it as an argument." msgstr "" #: ../../tutorial/classes.rst:764 msgid "" "Instance method objects have attributes, too: ``m.__self__`` is the instance" " object with the method :meth:`m`, and ``m.__func__`` is the function object" " corresponding to the method." msgstr "" #: ../../tutorial/classes.rst:772 msgid "Iterators" msgstr "" #: ../../tutorial/classes.rst:774 msgid "" "By now you have probably noticed that most container objects can be looped " "over using a :keyword:`for` statement::" msgstr "" #: ../../tutorial/classes.rst:788 msgid "" "This style of access is clear, concise, and convenient. The use of " "iterators pervades and unifies Python. Behind the scenes, the " ":keyword:`for` statement calls :func:`iter` on the container object. The " "function returns an iterator object that defines the method " ":meth:`~iterator.__next__` which accesses elements in the container one at a" " time. When there are no more elements, :meth:`~iterator.__next__` raises a" " :exc:`StopIteration` exception which tells the :keyword:`!for` loop to " "terminate. You can call the :meth:`~iterator.__next__` method using the " ":func:`next` built-in function; this example shows how it all works::" msgstr "" #: ../../tutorial/classes.rst:813 msgid "" "Having seen the mechanics behind the iterator protocol, it is easy to add " "iterator behavior to your classes. Define an :meth:`__iter__` method which " "returns an object with a :meth:`~iterator.__next__` method. If the class " "defines :meth:`__next__`, then :meth:`__iter__` can just return ``self``::" msgstr "" #: ../../tutorial/classes.rst:850 msgid "Generators" msgstr "" #: ../../tutorial/classes.rst:852 msgid "" ":term:`Generator`\\s are a simple and powerful tool for creating iterators." " They are written like regular functions but use the :keyword:`yield` " "statement whenever they want to return data. Each time :func:`next` is " "called on it, the generator resumes where it left off (it remembers all the " "data values and which statement was last executed). An example shows that " "generators can be trivially easy to create::" msgstr "" #: ../../tutorial/classes.rst:873 msgid "" "Anything that can be done with generators can also be done with class-based " "iterators as described in the previous section. What makes generators so " "compact is that the :meth:`__iter__` and :meth:`~generator.__next__` methods" " are created automatically." msgstr "" #: ../../tutorial/classes.rst:878 msgid "" "Another key feature is that the local variables and execution state are " "automatically saved between calls. This made the function easier to write " "and much more clear than an approach using instance variables like " "``self.index`` and ``self.data``." msgstr "" #: ../../tutorial/classes.rst:883 msgid "" "In addition to automatic method creation and saving program state, when " "generators terminate, they automatically raise :exc:`StopIteration`. In " "combination, these features make it easy to create iterators with no more " "effort than writing a regular function." msgstr "" #: ../../tutorial/classes.rst:892 msgid "Generator Expressions" msgstr "" #: ../../tutorial/classes.rst:894 msgid "" "Some simple generators can be coded succinctly as expressions using a syntax" " similar to list comprehensions but with parentheses instead of square " "brackets. These expressions are designed for situations where the generator " "is used right away by an enclosing function. Generator expressions are more" " compact but less versatile than full generator definitions and tend to be " "more memory friendly than equivalent list comprehensions." msgstr "" #: ../../tutorial/classes.rst:901 msgid "Examples::" msgstr "Contoh::" #: ../../tutorial/classes.rst:922 msgid "Footnotes" msgstr "Catatan kaki" #: ../../tutorial/classes.rst:923 msgid "" "Except for one thing. Module objects have a secret read-only attribute " "called :attr:`~object.__dict__` which returns the dictionary used to " "implement the module's namespace; the name :attr:`~object.__dict__` is an " "attribute but not a global name. Obviously, using this violates the " "abstraction of namespace implementation, and should be restricted to things " "like post-mortem debuggers." msgstr ""