Update of /cvsroot/python/python/dist/src/Doc/tut In directory sc8-pr-cvs1:/tmp/cvs-serv31014 Modified Files: glossary.tex Log Message: Lots of markup corrections. Some are minor, but others are not: the contents of an \item should not be enclosed in a group! Index: glossary.tex =================================================================== RCS file: /cvsroot/python/python/dist/src/Doc/tut/glossary.tex,v retrieving revision 1.2 retrieving revision 1.3 diff -C2 -d -r1.2 -r1.3 *** glossary.tex 27 Sep 2003 05:42:14 -0000 1.2 --- glossary.tex 27 Sep 2003 18:59:43 -0000 1.3 *************** *** 7,79 **** \index{...} ! \item[...]{The typical Python prompt of the interactive shell when entering ! code for an indented code block.} \index{>>>} ! \item[>>>]{The typical Python prompt of the interactive shell. Often seen ! for code examples that can be tried right away in the interpreter.} \index{__slots__} ! \item[__slots__]{A declaration inside a \emph{new-style class} that saves ! memory by pre-declaring space for instance attributes and eliminating ! instance dictionaries. Though popular, the technique is somewhat tricky to ! get right and is best reserved for rare cases where there are large numbers ! of instances in a memory critical application.} \index{BDFL} ! \item[BDFL]{Benevolent Dictator For Life, a.k.a. \ulink{Guido van ! Rossum}{http://www.python.org/~guido/}, Python's creator.} \index{byte code} ! \item[byte code]{The internal representation of a Python program in the ! interpreter. The byte code is also cached in the \code{.pyc} and ! {}\code{.pyo} files so that executing the same file is faster the second ! time (compilation from source to byte code can be saved). This ! "intermediate language" is said to run on a "virtual machine" that calls the ! subroutines corresponding to each bytecode.} \index{classic class} ! \item[classic class]{Any class which does not inherit from \class{object}. ! See new-style class.} \index{coercion} ! \item[coercion]{Converting data from one type to another. For example, ! {}\code{int(3.15)} coerces the floating point number to the integer, \code{3}. ! Most mathematical operations have rules for coercing their arguments to a common ! type. For instance, adding \code{3 + 4.5}, causes the integer \code{3} to be ! coerced to be a float \code{3.0} before adding to \code{4.5} resulting in the ! float \code{7.5}.} \index{descriptor} ! \item[descriptor]{Any object that defines the methods \method{__get__()}, ! \method{__set__()}, or \method{__delete__()}. When a class attribute is a ! descriptor, its special binding behavior is triggered upon attribute lookup. ! Normally, writing {}\var{a.b} looks up the object \var{b} in the class ! dictionary for \var{a}, but if \var{b} is a descriptor, the defined method ! gets called. Understanding descriptors is a key to a deep understanding of ! Python because they are the basis for many features including functions, ! methods, properties, class methods, static methods, and reference to super ! classes.} \index{dictionary} ! \item[dictionary]{An associative array, where arbitrary keys are mapped to ! values. The use of \class{dict} much resembles that for \class{list}, but ! the keys can be any object with a \function{__hash__} function, not just ! integers starting from zero. Called a hash in Perl.} \index{EAFP} ! \item[EAFP]{Easier to ask for forgiveness than permission. This common ! Python coding style assumes the existence of valid keys or attributes and ! catches exceptions if the assumption proves false. This clean and fast ! style is characterized by the presence of many \keyword{try} and ! {}\keyword{except} statements. The technique contrasts with the \emph{LBYL} ! style that is common in many other languages such as C.} \index{__future__} ! \item[__future__]{A pseudo module which programmers can use to enable ! new language features which are not compatible with the current interpreter. ! For example, the expression \code{11 / 4} currently evaluates to \code{2}. ! If the module in which it is executed had enabled emph{true division} by ! executing:} \begin{verbatim} --- 7,92 ---- \index{...} ! \item[\code{.\code{.}.}] ! The typical Python prompt of the interactive shell when entering code ! for an indented code block. \index{>>>} ! \item[\code{>\code{>}>}] ! The typical Python prompt of the interactive shell. Often seen for ! code examples that can be tried right away in the interpreter. \index{__slots__} ! \item[__slots__] ! A declaration inside a \emph{new-style class} that saves memory by ! pre-declaring space for instance attributes and eliminating instance ! dictionaries. Though popular, the technique is somewhat tricky to get ! right and is best reserved for rare cases where there are large ! numbers of instances in a memory critical application. \index{BDFL} ! \item[BDFL] ! Benevolent Dictator For Life, a.k.a. \ulink{Guido van ! Rossum}{http://www.python.org/~guido/}, Python's creator. \index{byte code} ! \item[byte code] ! The internal representation of a Python program in the interpreter. ! The byte code is also cached in the \code{.pyc} and \code{.pyo} ! files so that executing the same file is faster the second time ! (compilation from source to byte code can be saved). This ! \emph{intermediate language} is said to run on a \emph{virtual ! machine} that calls the subroutines corresponding to each bytecode. \index{classic class} ! \item[classic class] ! Any class which does not inherit from \class{object}. See ! \emph{new-style class}. \index{coercion} ! \item[coercion] ! Converting data from one type to another. For example, ! {}\code{int(3.15)} coerces the floating point number to the integer, ! {}\code{3}. Most mathematical operations have rules for coercing ! their arguments to a common type. For instance, adding \code{3 + ! 4.5}, causes the integer \code{3} to be coerced to be a float ! {}\code{3.0} before adding to \code{4.5} resulting in the float ! {}\code{7.5}. \index{descriptor} ! \item[descriptor] ! Any \emph{new-style} object that defines the methods ! {}\method{__get__()}, \method{__set__()}, or \method{__delete__()}. ! When a class attribute is a descriptor, its special binding behavior ! is triggered upon attribute lookup. Normally, writing \var{a.b} looks ! up the object \var{b} in the class dictionary for \var{a}, but if ! {}\var{b} is a descriptor, the defined method gets called. ! Understanding descriptors is a key to a deep understanding of Python ! because they are the basis for many features including functions, ! methods, properties, class methods, static methods, and reference to ! super classes. \index{dictionary} ! \item[dictionary] ! An associative array, where arbitrary keys are mapped to values. The ! use of \class{dict} much resembles that for \class{list}, but the keys ! can be any object with a \method{__hash__()} function, not just ! integers starting from zero. Called a hash in Perl. \index{EAFP} ! \item[EAFP] ! Easier to ask for forgiveness than permission. This common Python ! coding style assumes the existence of valid keys or attributes and ! catches exceptions if the assumption proves false. This clean and ! fast style is characterized by the presence of many \keyword{try} and ! {}\keyword{except} statements. The technique contrasts with the ! {}\emph{LBYL} style that is common in many other languages such as C. \index{__future__} ! \item[__future__] ! A pseudo module which programmers can use to enable new language ! features which are not compatible with the current interpreter. For ! example, the expression \code{11 / 4} currently evaluates to \code{2}. ! If the module in which it is executed had enabled emph{true division} ! by executing: \begin{verbatim} *************** *** 81,88 **** \end{verbatim} ! the expression \code{11 / 4} would evaluate to \code{2.75}. By actually ! importing the \module{__future__} module and evaluating its variables, you ! can see when a new feature was first added to the language and when it will ! become the default: \begin{verbatim} --- 94,101 ---- \end{verbatim} ! the expression \code{11 / 4} would evaluate to \code{2.75}. By ! actually importing the \refmodule[future]{__future__} module and ! evaluating its variables, you can see when a new feature was first ! added to the language and when it will become the default: \begin{verbatim} *************** *** 93,268 **** \index{generator} ! \item[generator]{A function that returns an iterator. It looks like a ! normal function except that the \keyword{yield} keyword is used instead of {}\keyword{return}. Generator functions often contain one or more ! {}\keyword{for} or \keyword{while} loops that \keyword{yield} elements back to ! the caller. The function execution is stopped at the \keyword{yield} keyword ! (returning the result) and is resumed there when the next element is ! requested by calling the \function{next()} method of the returned iterator.} \index{GIL} ! \item[GIL]{See \emph{global interpreter lock}.} \index{global interpreter lock} ! \item[global interpreter lock]{the lock used by Python threads to assure ! that only one thread can be run at a time. This simplifies Python by ! assuring that no two processes can access the same memory at the same time. ! Locking the entire interpreter makes it easier for the interpreter to be multi-threaded, at the expense of some parallelism on multi-processor ! machines. Efforts have been made in the past to create a "free-threaded" ! interpreter (one which locks shared data at a much finer granularity), but ! performance suffered in the common single-processor case.} \index{IDLE} ! \item[IDLE]{an Integrated Development Environment for Python. IDLE is a basic editor and interpreter environment that ships with the standard distribution of Python. Good for beginners, it also serves as clear example code for those wanting to implement a moderately ! sophisticated, multi-platform GUI application.} \index{immutable} ! \item[immutable]{A object with fixed value. Immutable objects are numbers, ! strings or tuples (and more). Such an object cannot be altered. A new object has to be created if a different value has to be stored. They play an ! important role in places where a constant hash value is needed. For example ! as a key in a dictionary.} \index{integer division} ! \item[integer division]{Mathematical division discarding any remainder. For ! example, the expression \code{11 / 4} currently evaluates to \code{2} in ! contrast to the \code{2.75} returned by float division. Also called ! \emph{floor division}. When dividing two integers the outcome will always be ! another integer (having the floor function applied to it). However, if one ! of the operands is another numeric type (such as a \class{float}), the result ! will be coerced (see \emph{coercion}) to a common type. For example, a integer ! divided by a float will result in a float value, possibly with a decimal ! fraction. Integer division can be forced by using the \code{//} operator ! instead of the \code{/} operator. ! See also, \emph{__future__}.} \index{interactive} ! \item[interactive]{Python has an interactive interpreter which means that ! you can try out things and directly see its result. Just launch ! {}\code{python} with no arguments (possibly by selecting it from your ! computer's main menu). It is a very powerful way to test out new ideas or ! inspect modules and packages (remember \code{help(x)}).} \index{interpreted} ! \item[interpreted]{Python is an interpreted language, opposed to a compiled ! one. This means that the source files can be run right away without first ! making an executable which is then run. Interpreted languages typically have a shorter development/debug cycle than compiled ones. See also ! {}\emph{interactive}.} \index{iterable} ! \item[iterable]{A container object capable of returning its members one at a ! time. Examples of iterables include all sequence types (such as\class{list}, {}\class{str}, and \class{tuple}) and some non-sequence types like ! {}\class{dict} and \class{file} and objects of any classes you define with ! an \method{__iter__} or \function{__getitem__} method. Iterables can be ! used in a \keyword{for} loop and in many other places where a sequence is ! needed (\function{zip}, \function{map}, ...). When an iterable object is ! passed as an argument to the builtin function \function{iter()}, it returns ! an iterator for the object. This iterator is good for one pass over the set ! of values. When using iterables, it is usually not necessary to call ! {}\function{iter()} or deal with iterator objects yourself - the \code{for} ! statement does that automatically for you, creating a temporary unnamed ! variable to hold the iterator for the duration of the loop. See also ! \emph{iterator}, \emph{sequence} and \emph{generator}.} \index{iterator} ! \item[iterator]{An object representing a stream of data. Repeated calls to ! the iterator's \function{next()} method return successive items in the stream. When no more data is available a \exception{StopIteration} ! exception is raised instead. At this point, the iterator object is exhausted ! and any further calls to its \function{next()} method just raise ! {}\exception{StopIteration} again. Iterators are required to have an ! {}\function{__iter__()} method that returns the iterator object itself so ! every iterator is also iterable and may be used in most places where other ! iterables are accepted. One notable exception is code that attempts ! multiple iteration passes. A container object (such as a \class{list}) ! produces a fresh new iterator each time you pass it to the \function{iter()} ! function or use it in a \function{for} loop. Attempting this with an iterator ! will just return the same exhausted iterator object from the second iteration ! pass, making it appear like an empty container.} \index{list comprehension} ! \item[list comprehension]{A compact way to process all or a subset of elements ! in a sequence and return a list with the results. \code{result = ["0x\%02x" \% x for x in range(256) if x \% 2 == 0]} generates a list of strings containing hex numbers (0x..) that are even and in the range from 0 to 255. The \keyword{if} clause is optional. If omitted, all elements in ! {}\code{range(256)} are processed in that case.} \index{mapping} ! \item[mapping]{A container object (such as \class{dict}) that supports ! arbitrary key lookups using the special method \function{__getitem__()}.} \index{metaclass} ! \item[metaclass]{The class of a class. Class definitions create a class ! name, a class dictionary, and a list of base classes. The metaclass is ! responsible for taking those three arguments and creating the class. Most ! object oriented programming languages provide a default implementation. ! What makes Python special is that it is possible to create custom ! metaclasses. Most users never need this tool, but when the need arises, ! metaclasses can provide powerful, elegant solutions. They have been used ! for logging attribute access, adding thread-safety, tracking object ! creation, implementing singletons, and many other tasks.} \index{LBYL} ! \item[LBYL]{Look before you leap. This coding style explicitly tests for ! pre-conditions before making calls or lookups. This style contrasts with ! the \emph{EAFP} approach and is characterized the presence of many ! {}\keyword{if} statements.} \index{mutable} ! \item[mutable]{Mutable objects can change their value but keep their ! \function{id()}. See also immutable.} \index{namespace} ! \item[namespace]{The place where a variable is stored. Namespaces are ! implemented as dictionary. There is the local, global and builtins ! namespace and the nested namespaces in objects (in methods). Namespaces ! support modularity by preventing naming conflicts. For instance, the ! functions \function{__builtins__.open()} and \function{os.open()} are ! distinguished by their namespaces. Namespaces also aid readability and ! maintainability by making it clear which modules implement a function. For ! instance, writing \function{random.seed()} or \function{itertools.izip()} ! makes it clear that those functions are implemented by the \module{random} ! and \module{itertools} modules respectively.} \index{nested scope} ! \item[nested scope]{The ability to refer to a variable in an enclosing ! definition. For instance, a function defined inside another function can ! refer to variables in the outer function. Note that nested scopes work only for reference and not for assignment which will always write to the ! innermost scope. In contrast, local variables both read and write in the ! innermost scope. Likewise, global variables read and write to the global ! namespace.} \index{new-style class} ! \item[new-style class]{Any class that inherits from \class{object}. This ! includes all built-in types like \class{list} and \class{dict}. Only ! new-style classes can use Python's newer, versatile features like ! {}\var{__slots__}, descriptors, properties, \var{__getattribute__}, class ! methods, and static methods.} \index{Python3000} ! \item[Python3000]{A mythical python release, allowed not to be backward ! compatible, with telepathic interface.} \index{sequence} ! \item[sequence]{An \emph{iterable} which supports efficient element access using ! integer indices via the \function{__getitem__} and \function{__len()__} ! special methods. Some builtin sequence types are \class{list}, \class{str}, ! {}\class{tuple}, and \class{unicode}. Note that \class{dict} also supports ! {}\function{__getitem__} and \function{__len__}, but is considered a mapping ! rather than a sequence because the lookups use arbitrary \emph{immutable} keys ! rather than integers.} \index{Zen of Python} ! \item[Zen of Python]{listing of Python design principles and philosophies ! that are helpful in understanding and using the language. The listing can ! be found by typing \code{import this} at the interactive prompt.} \end{description} --- 106,309 ---- \index{generator} ! \item[generator] ! A function that returns an iterator. It looks like a normal function ! except that the \keyword{yield} keyword is used instead of {}\keyword{return}. Generator functions often contain one or more ! {}\keyword{for} or \keyword{while} loops that \keyword{yield} elements ! back to the caller. The function execution is stopped at the ! {}\keyword{yield} keyword (returning the result) and is resumed there ! when the next element is requested by calling the \method{next()} ! method of the returned iterator. \index{GIL} ! \item[GIL] ! See \emph{global interpreter lock}. \index{global interpreter lock} ! \item[global interpreter lock] ! The lock used by Python threads to assure that only one thread can be ! run at a time. This simplifies Python by assuring that no two ! processes can access the same memory at the same time. Locking the ! entire interpreter makes it easier for the interpreter to be multi-threaded, at the expense of some parallelism on multi-processor ! machines. Efforts have been made in the past to create a ! "free-threaded" interpreter (one which locks shared data at a much ! finer granularity), but performance suffered in the common ! single-processor case. \index{IDLE} ! \item[IDLE] ! An Integrated Development Environment for Python. IDLE is a basic editor and interpreter environment that ships with the standard distribution of Python. Good for beginners, it also serves as clear example code for those wanting to implement a moderately ! sophisticated, multi-platform GUI application. \index{immutable} ! \item[immutable] ! A object with fixed value. Immutable objects are numbers, strings or ! tuples (and more). Such an object cannot be altered. A new object has to be created if a different value has to be stored. They play an ! important role in places where a constant hash value is needed. For ! example as a key in a dictionary. \index{integer division} ! \item[integer division] ! Mathematical division discarding any remainder. For example, the ! expression \code{11 / 4} currently evaluates to \code{2} in contrast ! to the \code{2.75} returned by float division. Also called ! {}\emph{floor division}. When dividing two integers the outcome will ! always be another integer (having the floor function applied to it). ! However, if one of the operands is another numeric type (such as a ! {}\class{float}), the result will be coerced (see \emph{coercion}) to ! a common type. For example, a integer divided by a float will result ! in a float value, possibly with a decimal fraction. Integer division ! can be forced by using the \code{//} operator instead of the \code{/} ! operator. See also \emph{__future__}. \index{interactive} ! \item[interactive] ! Python has an interactive interpreter which means that you can try out ! things and directly see its result. Just launch \code{python} with no ! arguments (possibly by selecting it from your computer's main menu). ! It is a very powerful way to test out new ideas or inspect modules and ! packages (remember \code{help(x)}). \index{interpreted} ! \item[interpreted] ! Python is an interpreted language, opposed to a compiled one. This ! means that the source files can be run right away without first making ! an executable which is then run. Interpreted languages typically have a shorter development/debug cycle than compiled ones. See also ! {}\emph{interactive}. \index{iterable} ! \item[iterable] ! A container object capable of returning its members one at a time. ! Examples of iterables include all sequence types (such as\class{list}, {}\class{str}, and \class{tuple}) and some non-sequence types like ! {}\class{dict} and \class{file} and objects of any classes you define ! with an \method{__iter__()} or \method{__getitem__()} method. Iterables ! can be used in a \keyword{for} loop and in many other places where a ! sequence is needed (\function{zip()}, \function{map()}, ...). When an ! iterable object is passed as an argument to the builtin function ! {}\function{iter()}, it returns an iterator for the object. This ! iterator is good for one pass over the set of values. When using ! iterables, it is usually not necessary to call \function{iter()} or ! deal with iterator objects yourself---the \code{for} statement does ! that automatically for you, creating a temporary unnamed variable to ! hold the iterator for the duration of the loop. See also ! {}\emph{iterator}, \emph{sequence}, and \emph{generator}. \index{iterator} ! \item[iterator] ! An object representing a stream of data. Repeated calls to the ! iterator's \method{next()} method return successive items in the stream. When no more data is available a \exception{StopIteration} ! exception is raised instead. At this point, the iterator object is ! exhausted and any further calls to its \method{next()} method just ! raise \exception{StopIteration} again. Iterators are required to have ! an \method{__iter__()} method that returns the iterator object ! itself so every iterator is also iterable and may be used in most ! places where other iterables are accepted. One notable exception is ! code that attempts multiple iteration passes. A container object ! (such as a \class{list}) produces a fresh new iterator each time you ! pass it to the \function{iter()} function or use it in a ! {}\keyword{for} loop. Attempting this with an iterator will just ! return the same exhausted iterator object from the second iteration ! pass, making it appear like an empty container. \index{list comprehension} ! \item[list comprehension] ! A compact way to process all or a subset of elements in a sequence and ! return a list with the results. \code{result = ["0x\%02x" \% x for x in range(256) if x \% 2 == 0]} generates a list of strings containing hex numbers (0x..) that are even and in the range from 0 to 255. The \keyword{if} clause is optional. If omitted, all elements in ! {}\code{range(256)} are processed in that case. \index{mapping} ! \item[mapping] ! A container object (such as \class{dict}) that supports arbitrary key ! lookups using the special method \method{__getitem__()}. \index{metaclass} ! \item[metaclass] ! The class of a class. Class definitions create a class name, a class ! dictionary, and a list of base classes. The metaclass is responsible ! for taking those three arguments and creating the class. Most object ! oriented programming languages provide a default implementation. What ! makes Python special is that it is possible to create custom ! metaclasses. Most users never need this tool, but when the need ! arises, metaclasses can provide powerful, elegant solutions. They ! have been used for logging attribute access, adding thread-safety, ! tracking object creation, implementing singletons, and many other ! tasks. \index{LBYL} ! \item[LBYL] ! Look before you leap. This coding style explicitly tests for ! pre-conditions before making calls or lookups. This style contrasts ! with the \emph{EAFP} approach and is characterized the presence of ! many \keyword{if} statements. \index{mutable} ! \item[mutable] ! Mutable objects can change their value but keep their \function{id()}. ! See also \emph{immutable}. \index{namespace} ! \item[namespace] ! The place where a variable is stored. Namespaces are implemented as ! dictionary. There is the local, global and builtins namespace and the ! nested namespaces in objects (in methods). Namespaces support ! modularity by preventing naming conflicts. For instance, the ! functions \function{__builtin__.open()} and \function{os.open()} are ! distinguished by their namespaces. Namespaces also aid readability ! and maintainability by making it clear which modules implement a ! function. For instance, writing \function{random.seed()} or ! {}\function{itertools.izip()} makes it clear that those functions are ! implemented by the \refmodule{random} and \refmodule{itertools} ! modules respectively. \index{nested scope} ! \item[nested scope] ! The ability to refer to a variable in an enclosing definition. For ! instance, a function defined inside another function can refer to ! variables in the outer function. Note that nested scopes work only for reference and not for assignment which will always write to the ! innermost scope. In contrast, local variables both read and write in ! the innermost scope. Likewise, global variables read and write to the ! global namespace. \index{new-style class} ! \item[new-style class] ! Any class that inherits from \class{object}. This includes all ! built-in types like \class{list} and \class{dict}. Only new-style ! classes can use Python's newer, versatile features like ! {}\var{__slots__}, descriptors, properties, ! \method{__getattribute__()}, class methods, and static methods. \index{Python3000} ! \item[Python3000] ! A mythical python release, allowed not to be backward compatible, with ! telepathic interface. \index{sequence} ! \item[sequence] ! An \emph{iterable} which supports efficient element access using ! integer indices via the \method{__getitem__()} and ! {}\method{__len__()} special methods. Some built-in sequence types ! are \class{list}, \class{str}, \class{tuple}, and \class{unicode}. ! Note that \class{dict} also supports \method{__getitem__()} and ! {}\method{__len__()}, but is considered a mapping rather than a ! sequence because the lookups use arbitrary \emph{immutable} keys ! rather than integers. \index{Zen of Python} ! \item[Zen of Python] ! Listing of Python design principles and philosophies that are helpful ! in understanding and using the language. The listing can be found by ! typing \code{import this} at the interactive prompt. \end{description}