diff options
Diffstat (limited to 'Doc/ref')
| -rw-r--r-- | Doc/ref/ref1.tex | 2 | ||||
| -rw-r--r-- | Doc/ref/ref3.tex | 97 | ||||
| -rw-r--r-- | Doc/ref/ref5.tex | 186 | ||||
| -rw-r--r-- | Doc/ref/ref6.tex | 34 | ||||
| -rw-r--r-- | Doc/ref/ref7.tex | 2 |
5 files changed, 237 insertions, 84 deletions
diff --git a/Doc/ref/ref1.tex b/Doc/ref/ref1.tex index 15bcf36..6234716 100644 --- a/Doc/ref/ref1.tex +++ b/Doc/ref/ref1.tex @@ -93,7 +93,7 @@ grammar notation. This uses the following style of definition: \index{syntax} \index{notation} -\begin{productionlist} +\begin{productionlist}[*] \production{name}{\token{lc_letter} (\token{lc_letter} | "_")*} \production{lc_letter}{"a"..."z"} \end{productionlist} diff --git a/Doc/ref/ref3.tex b/Doc/ref/ref3.tex index 40b2ebd..8340e17 100644 --- a/Doc/ref/ref3.tex +++ b/Doc/ref/ref3.tex @@ -218,7 +218,7 @@ when using mixed operands. \indexii{integer}{representation} \item[Floating point numbers] -These represent machine-level double precision floating point numbers. +These represent machine-level double precision floating point numbers. You are at the mercy of the underlying machine architecture (and C or Java implementation) for the accepted range and handling of overflow. Python does not support single-precision floating point numbers; the @@ -470,7 +470,7 @@ parameter list. \obindex{function} \obindex{user-defined function} -Special attributes: +Special attributes: \begin{tableiii}{lll}{member}{Attribute}{Meaning}{} \lineiii{__doc__}{The function's documentation string, or @@ -860,12 +860,12 @@ but they are mentioned here for completeness. \begin{description} \item[Code objects] -Code objects represent \emph{byte-compiled} executable Python code, or +Code objects represent \emph{byte-compiled} executable Python code, or \emph{bytecode}. The difference between a code object and a function object is that the function object contains an explicit reference to the function's globals (the module in which it -was defined), while a code object contains no context; +was defined), while a code object contains no context; also the default argument values are stored in the function object, not in the code object (because they represent values calculated at run-time). Unlike function objects, code objects are immutable and @@ -1069,7 +1069,7 @@ by the built-in \function{classmethod()} constructor. %========================================================================= \section{New-style and classic classes} -Classes and instances come in two flavors: old-style or classic, and new-style. +Classes and instances come in two flavors: old-style or classic, and new-style. Up to Python 2.1, old-style classes were the only flavour available to the user. The concept of (old-style) class is unrelated to the concept of type: if @@ -1244,7 +1244,7 @@ description...}>} should be returned. The return value must be a string object. If a class defines \method{__repr__()} but not \method{__str__()}, then \method{__repr__()} is also used when an ``informal'' string -representation of instances of that class is required. +representation of instances of that class is required. This is typically used for debugging, so it is important that the representation is information-rich and unambiguous. @@ -1280,10 +1280,14 @@ follows: \code{\var{x}!=\var{y}} calls \code{\var{x}.__ne__(\var{y})}, \code{\var{x}>\var{y}} calls \code{\var{x}.__gt__(\var{y})}, and \code{\var{x}>=\var{y}} calls \code{\var{x}.__ge__(\var{y})}. -These methods can return any value, but if the comparison operator is -used in a Boolean context, the return value should be interpretable as -a Boolean value, else a \exception{TypeError} will be raised. -By convention, \code{False} is used for false and \code{True} for true. + +A rich comparison method may return the singleton \code{NotImplemented} if it +does not implement the operation for a given pair of arguments. +By convention, \code{False} and \code{True} are returned for a successful +comparison. However, these methods can return any value, so if the +comparison operator is used in a Boolean context (e.g., in the condition +of an \code{if} statement), Python will call \function{bool()} on the +value to determine if the result is true or false. There are no implied relationships among the comparison operators. The truth of \code{\var{x}==\var{y}} does not imply that \code{\var{x}!=\var{y}} @@ -1297,9 +1301,7 @@ the right argument does); rather, \method{__lt__()} and \method{__ge__()} are each other's reflection, and \method{__eq__()} and \method{__ne__()} are their own reflection. -Arguments to rich comparison methods are never coerced. A rich -comparison method may return \code{NotImplemented} if it does not -implement the operation for a given pair of arguments. +Arguments to rich comparison methods are never coerced. \end{methoddesc} \begin{methoddesc}[object]{__cmp__}{self, other} @@ -1399,7 +1401,7 @@ instead of the normal mechanism (i.e.\ store the value in the instance dictionary). \var{name} is the attribute name, \var{value} is the value to be assigned to it. -If \method{__setattr__()} wants to assign to an instance attribute, it +If \method{__setattr__()} wants to assign to an instance attribute, it should not simply execute \samp{self.\var{name} = value} --- this would cause a recursive call to itself. Instead, it should insert the value in the dictionary of instance attributes, e.g., @@ -1422,8 +1424,8 @@ The following methods only apply to new-style classes. \begin{methoddesc}[object]{__getattribute__}{self, name} Called unconditionally to implement attribute accesses for instances -of the class. If the class also defines \method{__getattr__()}, the latter -will not be called unless \method{__getattribute__()} either calls it +of the class. If the class also defines \method{__getattr__()}, the latter +will not be called unless \method{__getattribute__()} either calls it explicitly or raises an \exception{AttributeError}. This method should return the (computed) attribute value or raise an \exception{AttributeError} exception. @@ -1475,7 +1477,7 @@ descriptor. The default behavior for attribute access is to get, set, or delete the attribute from an object's dictionary. For instance, \code{a.x} has a lookup chain starting with \code{a.__dict__['x']}, then -\code{type(a).__dict__['x']}, and continuing +\code{type(a).__dict__['x']}, and continuing through the base classes of \code{type(a)} excluding metaclasses. However, if the looked-up value is an object defining one of the descriptor @@ -1489,14 +1491,14 @@ The starting point for descriptor invocation is a binding, \code{a.x}. How the arguments are assembled depends on \code{a}: \begin{itemize} - + \item[Direct Call] The simplest and least common call is when user code directly invokes a descriptor method: \code{x.__get__(a)}. \item[Instance Binding] If binding to a new-style object instance, \code{a.x} is transformed into the call: \code{type(a).__dict__['x'].__get__(a, type(a))}. - + \item[Class Binding] If binding to a new-style class, \code{A.x} is transformed into the call: \code{A.__dict__['x'].__get__(None, A)}. @@ -1505,7 +1507,7 @@ How the arguments are assembled depends on \code{a}: \code{obj.__class__.__mro__} for the base class \code{A} immediately preceding \code{B} and then invokes the descriptor with the call: \code{A.__dict__['m'].__get__(obj, A)}. - + \end{itemize} For instance bindings, the precedence of descriptor invocation depends @@ -1518,7 +1520,7 @@ descriptors can be overridden by instances. Python methods (including \function{staticmethod()} and \function{classmethod()}) are implemented as non-data descriptors. Accordingly, instances can redefine and override methods. This allows individual instances to acquire -behaviors that differ from other instances of the same class. +behaviors that differ from other instances of the same class. The \function{property()} function is implemented as a data descriptor. Accordingly, instances cannot override the behavior of a property. @@ -1536,14 +1538,14 @@ definition. The \var{__slots__} declaration takes a sequence of instance variables and reserves just enough space in each instance to hold a value for each variable. Space is saved because \var{__dict__} is not created for each instance. - + \begin{datadesc}{__slots__} This class variable can be assigned a string, iterable, or sequence of strings with variable names used by instances. If defined in a new-style class, \var{__slots__} reserves space for the declared variables and prevents the automatic creation of \var{__dict__} and \var{__weakref__} for each instance. -\versionadded{2.2} +\versionadded{2.2} \end{datadesc} \noindent @@ -1555,23 +1557,23 @@ Notes on using \var{__slots__} variables not listed in the \var{__slots__} definition. Attempts to assign to an unlisted variable name raises \exception{AttributeError}. If dynamic assignment of new variables is desired, then add \code{'__dict__'} to the -sequence of strings in the \var{__slots__} declaration. +sequence of strings in the \var{__slots__} declaration. \versionchanged[Previously, adding \code{'__dict__'} to the \var{__slots__} declaration would not enable the assignment of new attributes not -specifically listed in the sequence of instance variable names]{2.3} +specifically listed in the sequence of instance variable names]{2.3} \item Without a \var{__weakref__} variable for each instance, classes defining \var{__slots__} do not support weak references to its instances. If weak reference support is needed, then add \code{'__weakref__'} to the -sequence of strings in the \var{__slots__} declaration. +sequence of strings in the \var{__slots__} declaration. \versionchanged[Previously, adding \code{'__weakref__'} to the \var{__slots__} -declaration would not enable support for weak references]{2.3} +declaration would not enable support for weak references]{2.3} \item \var{__slots__} are implemented at the class level by creating descriptors (\ref{descriptors}) for each variable name. As a result, class attributes cannot be used to set default values for instance variables defined by \var{__slots__}; otherwise, the class attribute would -overwrite the descriptor assignment. +overwrite the descriptor assignment. \item If a class defines a slot also defined in a base class, the instance variable defined by the base class slot is inaccessible (except by retrieving @@ -1580,14 +1582,19 @@ program undefined. In the future, a check may be added to prevent this. \item The action of a \var{__slots__} declaration is limited to the class where it is defined. As a result, subclasses will have a \var{__dict__} -unless they also define \var{__slots__}. +unless they also define \var{__slots__}. \item \var{__slots__} do not work for classes derived from ``variable-length'' -built-in types such as \class{long}, \class{str} and \class{tuple}. +built-in types such as \class{long}, \class{str} and \class{tuple}. \item Any non-string iterable may be assigned to \var{__slots__}. Mappings may also be used; however, in the future, special meaning may -be assigned to the values corresponding to each key. +be assigned to the values corresponding to each key. + +\item \var{__class__} assignment works only if both classes have the +same \var{__slots__}. +\versionchanged[Previously, \var{__class__} assignment raised an error +if either new or old class had \var{__slots__}]{2.6} \end{itemize} @@ -1613,7 +1620,7 @@ the role of a factory function. This variable can be any callable accepting arguments for \code{name}, \code{bases}, and \code{dict}. Upon class creation, the callable is used instead of the built-in \function{type()}. -\versionadded{2.2} +\versionadded{2.2} \end{datadesc} The appropriate metaclass is determined by the following precedence rules: @@ -1630,7 +1637,7 @@ type). \item Otherwise, the old-style, classic metaclass (types.ClassType) is used. -\end{itemize} +\end{itemize} The potential uses for metaclasses are boundless. Some ideas that have been explored including logging, interface checking, automatic delegation, @@ -1663,15 +1670,15 @@ defined to handle simple, but not extended slices.) It is also recommended that mappings provide the methods \method{keys()}, \method{values()}, \method{items()}, \method{has_key()}, \method{get()}, \method{clear()}, \method{setdefault()}, \method{iterkeys()}, \method{itervalues()}, -\method{iteritems()}, \method{pop()}, \method{popitem()}, +\method{iteritems()}, \method{pop()}, \method{popitem()}, \method{copy()}, and \method{update()} behaving similar to those for Python's standard dictionary objects. The \module{UserDict} module provides a \class{DictMixin} class to help create those methods from a base set of \method{__getitem__()}, \method{__setitem__()}, -\method{__delitem__()}, and \method{keys()}. +\method{__delitem__()}, and \method{keys()}. Mutable sequences should provide methods \method{append()}, \method{count()}, \method{index()}, -\method{extend()}, +\method{extend()}, \method{insert()}, \method{pop()}, \method{remove()}, \method{reverse()} and \method{sort()}, like Python standard list objects. Finally, sequence types should implement addition (meaning concatenation) and @@ -1694,12 +1701,12 @@ through the values. \ttindex{items()} \ttindex{iterkeys()} \ttindex{itervalues()} - \ttindex{iteritems()} + \ttindex{iteritems()} \ttindex{has_key()} \ttindex{get()} \ttindex{setdefault()} - \ttindex{pop()} - \ttindex{popitem()} + \ttindex{pop()} + \ttindex{popitem()} \ttindex{clear()} \ttindex{copy()} \ttindex{update()} @@ -1707,7 +1714,7 @@ through the values. \withsubitem{(sequence object method)}{ \ttindex{append()} \ttindex{count()} - \ttindex{extend()} + \ttindex{extend()} \ttindex{index()} \ttindex{insert()} \ttindex{pop()} @@ -1721,7 +1728,7 @@ through the values. \ttindex{__rmul__()} \ttindex{__imul__()} \ttindex{__contains__()} - \ttindex{__iter__()}} + \ttindex{__iter__()}} \withsubitem{(numeric object method)} \begin{methoddesc}[container object]{__len__}{self} @@ -1744,7 +1751,7 @@ raised; if of a value outside the set of indexes for the sequence (after any special interpretation of negative values), \exception{IndexError} should be raised. For mapping types, if \var{key} is missing (not in the container), -\exception{KeyError} should be raised. +\exception{KeyError} should be raised. \note{\keyword{for} loops expect that an \exception{IndexError} will be raised for illegal indexes to allow proper detection of the end of the sequence.} @@ -1943,7 +1950,7 @@ the alternate context; \exception{TypeError} will be raised instead. \methodline[numeric object]{__rmul__}{self, other} \methodline[numeric object]{__rdiv__}{self, other} \methodline[numeric object]{__rtruediv__}{self, other} -\methodline[numeric object]{__rfloordiv__}{self, other} +\methodline[numeric object]{__rfloordiv__}{self, other} \methodline[numeric object]{__rmod__}{self, other} \methodline[numeric object]{__rdivmod__}{self, other} \methodline[numeric object]{__rpow__}{self, other} @@ -1964,7 +1971,7 @@ operands are of different types.\footnote{ For operands of the same type, it is assumed that if the non-reflected method (such as \method{__add__()}) fails the operation is not supported, which is why the reflected method - is not called.} + is not called.} For instance, to evaluate the expression \var{x}\code{-}\var{y}, where \var{y} is an instance of a class that has an \method{__rsub__()} method, \code{\var{y}.__rsub__(\var{x})} @@ -1989,7 +1996,7 @@ complicated). \methodline[numeric object]{__idiv__}{self, other} \methodline[numeric object]{__itruediv__}{self, other} \methodline[numeric object]{__ifloordiv__}{self, other} -\methodline[numeric object]{__imod__}{self, other} +\methodline[numeric object]{__imod__}{self, other} \methodline[numeric object]{__ipow__}{self, other\optional{, modulo}} \methodline[numeric object]{__ilshift__}{self, other} \methodline[numeric object]{__irshift__}{self, other} diff --git a/Doc/ref/ref5.tex b/Doc/ref/ref5.tex index 0b4e978..9a4fe3a 100644 --- a/Doc/ref/ref5.tex +++ b/Doc/ref/ref5.tex @@ -56,7 +56,7 @@ categorized syntactically as atoms. The syntax for atoms is: \production{enclosure} {\token{parenth_form} | \token{list_display}} \productioncont{| \token{generator_expression} | \token{dict_display}} - \productioncont{| \token{string_conversion}} + \productioncont{| \token{string_conversion} | \token{yield_atom}} \end{productionlist} @@ -65,6 +65,7 @@ categorized syntactically as atoms. The syntax for atoms is: \index{identifier} An identifier occurring as an atom is a name. See +section \ref{identifiers} for lexical definition and section~\ref{naming} for documentation of naming and binding. When the name is bound to an object, evaluation of the atom yields @@ -154,22 +155,20 @@ A list display is a possibly empty series of expressions enclosed in square brackets: \begin{productionlist} - \production{test} - {\token{or_test} | \token{lambda_form}} - \production{testlist} - {\token{test} ( "," \token{test} )* [ "," ]} \production{list_display} - {"[" [\token{listmaker}] "]"} - \production{listmaker} - {\token{expression} ( \token{list_for} - | ( "," \token{expression} )* [","] )} - \production{list_iter} - {\token{list_for} | \token{list_if}} + {"[" [\token{expression_list} | \token{list_comprehension}] "]"} + \production{list_comprehension} + {\token{expression} \token{list_for}} \production{list_for} - {"for" \token{expression_list} "in" \token{testlist} + {"for" \token{target_list} "in" \token{old_expression_list} [\token{list_iter}]} + \production{old_expression_list} + {\token{old_expression} + [("," \token{old_expression})+ [","]]} + \production{list_iter} + {\token{list_for} | \token{list_if}} \production{list_if} - {"if" \token{test} [\token{list_iter}]} + {"if" \token{old_expression} [\token{list_iter}]} \end{productionlist} A list display yields a new list object. Its contents are specified @@ -200,19 +199,18 @@ A generator expression is a compact generator notation in parentheses: \begin{productionlist} \production{generator_expression} - {"(" \token{test} \token{genexpr_for} ")"} + {"(" \token{expression} \token{genexpr_for} ")"} \production{genexpr_for} - {"for" \token{expression_list} "in" \token{test} + {"for" \token{target_list} "in" \token{or_test} [\token{genexpr_iter}]} \production{genexpr_iter} {\token{genexpr_for} | \token{genexpr_if}} \production{genexpr_if} - {"if" \token{test} [\token{genexpr_iter}]} + {"if" \token{old_expression} [\token{genexpr_iter}]} \end{productionlist} A generator expression yields a new generator object. \obindex{generator} -\obindex{generator expression} It consists of a single expression followed by at least one \keyword{for} clause and zero or more \keyword{for} or \keyword{if} clauses. The iterating values of the new generator are those that @@ -268,6 +266,142 @@ stored for a given key value prevails. \indexii{immutable}{object} +\subsection{Yield expressions\label{yieldexpr}} +\kwindex{yield} +\indexii{yield}{expression} +\indexii{generator}{function} + +\begin{productionlist} + \production{yield_atom} + {"(" \token{yield_expression} ")"} + \production{yield_expression} + {"yield" [\token{expression_list}]} +\end{productionlist} + +\versionadded{2.5} + +The \keyword{yield} expression is only used when defining a generator +function, and can only be used in the body of a function definition. +Using a \keyword{yield} expression in a function definition is +sufficient to cause that definition to create a generator function +instead of a normal function. + +When a generator function is called, it returns an iterator known as a +generator. That generator then controls the execution of a generator +function. The execution starts when one of the generator's methods is +called. At that time, the execution proceeds to the first +\keyword{yield} expression, where it is suspended again, returning the +value of \grammartoken{expression_list} to generator's caller. By +suspended we mean that all local state is retained, including the +current bindings of local variables, the instruction pointer, and the +internal evaluation stack. When the execution is resumed by calling +one of the generator's methods, the function can proceed exactly as +if the \keyword{yield} expression was just another external call. +The value of the \keyword{yield} expression after resuming depends on +the method which resumed the execution. + +\index{coroutine} + +All of this makes generator functions quite similar to coroutines; they +yield multiple times, they have more than one entry point and their +execution can be suspended. The only difference is that a generator +function cannot control where should the execution continue after it +yields; the control is always transfered to the generator's caller. + +\obindex{generator} + +The following generator's methods can be used to control the execution +of a generator function: + +\exindex{StopIteration} + +\begin{methoddesc}[generator]{next}{} + Starts the execution of a generator function or resumes it at the + last executed \keyword{yield} expression. When a generator function + is resumed with a \method{next()} method, the current \keyword{yield} + expression always evaluates to \constant{None}. The execution then + continues to the next \keyword{yield} expression, where the generator + is suspended again, and the value of the + \grammartoken{expression_list} is returned to \method{next()}'s + caller. If the generator exits without yielding another value, a + \exception{StopIteration} exception is raised. +\end{methoddesc} + +\begin{methoddesc}[generator]{send}{value} + Resumes the execution and ``sends'' a value into the generator + function. The \code{value} argument becomes the result of the + current \keyword{yield} expression. The \method{send()} method + returns the next value yielded by the generator, or raises + \exception{StopIteration} if the generator exits without yielding + another value. + When \method{send()} is called to start the generator, it must be + called with \constant{None} as the argument, because there is no + \keyword{yield} expression that could receieve the value. +\end{methoddesc} + +\begin{methoddesc}[generator]{throw} + {type\optional{, value\optional{, traceback}}} + Raises an exception of type \code{type} at the point where generator + was paused, and returns the next value yielded by the generator + function. If the generator exits without yielding another value, a + \exception{StopIteration} exception is raised. If the generator + function does not catch the passed-in exception, or raises a + different exception, then that exception propagates to the caller. +\end{methoddesc} + +\exindex{GeneratorExit} + +\begin{methoddesc}[generator]{close}{} + Raises a \exception{GeneratorExit} at the point where the generator + function was paused. If the generator function then raises + \exception{StopIteration} (by exiting normally, or due to already + being closed) or \exception{GeneratorExit} (by not catching the + exception), close returns to its caller. If the generator yields a + value, a \exception{RuntimeError} is raised. If the generator raises + any other exception, it is propagated to the caller. \method{close} + does nothing if the generator has already exited due to an exception + or normal exit. +\end{methoddesc} + +Here is a simple example that demonstrates the behavior of generators +and generator functions: + +\begin{verbatim} +>>> def echo(value=None): +... print "Execution starts when 'next()' is called for the first time." +... try: +... while True: +... try: +... value = (yield value) +... except GeneratorExit: +... # never catch GeneratorExit +... raise +... except Exception, e: +... value = e +... finally: +... print "Don't forget to clean up when 'close()' is called." +... +>>> generator = echo(1) +>>> print generator.next() +Execution starts when 'next()' is called for the first time. +1 +>>> print generator.next() +None +>>> print generator.send(2) +2 +>>> generator.throw(TypeError, "spam") +TypeError('spam',) +>>> generator.close() +Don't forget to clean up when 'close()' is called. +\end{verbatim} + +\begin{seealso} + \seepep{0342}{Coroutines via Enhanced Generators} + {The proposal to enhance the API and syntax of generators, + making them usable as simple coroutines.} +\end{seealso} + + \section{Primaries\label{primaries}} \index{primary} @@ -430,9 +564,8 @@ series of arguments: \begin{productionlist} \production{call} - {\token{primary} "(" [\token{argument_list} [","]] ")"} - {\token{primary} "(" [\token{argument_list} [","] | - \token{test} \token{genexpr_for} ] ")"} + {\token{primary} "(" [\token{argument_list} [","]} + \productioncont{ | \token{expression} \token{genexpr_for}] ")"} \production{argument_list} {\token{positional_arguments} ["," \token{keyword_arguments}]} \productioncont{ ["," "*" \token{expression}]} @@ -765,10 +898,9 @@ The shifting operations have lower priority than the arithmetic operations: \begin{productionlist} - % The empty groups below prevent conversion to guillemets. \production{shift_expr} {\token{a_expr} - | \token{shift_expr} ( "<{}<" | ">{}>" ) \token{a_expr}} + | \token{shift_expr} ( "<<" | ">>" ) \token{a_expr}} \end{productionlist} These operators accept plain or long integers as arguments. The @@ -966,14 +1098,18 @@ truth value. \section{Boolean operations\label{Booleans}} +\indexii{Conditional}{expression} \indexii{Boolean}{operation} Boolean operations have the lowest priority of all Python operations: \begin{productionlist} \production{expression} - {\token{or_test} [\token{if} \token{or_test} \token{else} - \token{test}] | \token{lambda_form}} + {\token{conditional_expression} | \token{lambda_form}} + \production{old_expression} + {\token{or_test} | \token{old_lambda_form}} + \production{conditional_expression} + {\token{or_test} ["if" \token{or_test} "else" \token{expression}]} \production{or_test} {\token{and_test} | \token{or_test} "or" \token{and_test}} \production{and_test} @@ -1025,6 +1161,8 @@ not \code{''}.) \begin{productionlist} \production{lambda_form} {"lambda" [\token{parameter_list}]: \token{expression}} + \production{old_lambda_form} + {"lambda" [\token{parameter_list}]: \token{old_expression}} \end{productionlist} Lambda forms (lambda expressions) have the same syntactic position as diff --git a/Doc/ref/ref6.tex b/Doc/ref/ref6.tex index e92a63d..60e7b02 100644 --- a/Doc/ref/ref6.tex +++ b/Doc/ref/ref6.tex @@ -106,7 +106,8 @@ objects: \begin{productionlist} \production{assignment_stmt} - {(\token{target_list} "=")+ \token{expression_list}} + {(\token{target_list} "=")+ + (\token{expression_list} | \token{yield_expression})} \production{target_list} {\token{target} ("," \token{target})* [","]} \production{target} @@ -271,11 +272,11 @@ operation and an assignment statement: \begin{productionlist} \production{augmented_assignment_stmt} - {\token{target} \token{augop} \token{expression_list}} + {\token{target} \token{augop} + (\token{expression_list} | \token{yield_expression})} \production{augop} {"+=" | "-=" | "*=" | "/=" | "\%=" | "**="} - % The empty groups below prevent conversion to guillemets. - \productioncont{| ">{}>=" | "<{}<=" | "\&=" | "\textasciicircum=" | "|="} + \productioncont{| ">>=" | "<<=" | "\&=" | "\textasciicircum=" | "|="} \end{productionlist} (See section~\ref{primaries} for the syntax definitions for the last @@ -404,7 +405,7 @@ to include an \grammartoken{expression_list}. In that context, a bare \begin{productionlist} \production{yield_stmt} - {"yield" \token{expression_list}} + {\token{yield_expression}} \end{productionlist} \index{generator!function} @@ -573,15 +574,19 @@ It continues with the next cycle of the nearest enclosing loop. \production{import_stmt} {"import" \token{module} ["as" \token{name}] ( "," \token{module} ["as" \token{name}] )*} - \productioncont{| "from" \token{module} "import" \token{identifier} + \productioncont{| "from" \token{relative_module} "import" \token{identifier} ["as" \token{name}]} \productioncont{ ( "," \token{identifier} ["as" \token{name}] )*} - \productioncont{| "from" \token{module} "import" "(" \token{identifier} - ["as" \token{name}]} + \productioncont{| "from" \token{relative_module} "import" "(" + \token{identifier} ["as" \token{name}]} \productioncont{ ( "," \token{identifier} ["as" \token{name}] )* [","] ")"} \productioncont{| "from" \token{module} "import" "*"} \production{module} {(\token{identifier} ".")* \token{identifier}} + \production{relative_module} + {"."* \token{module} | "."+} + \production{name} + {\token{identifier}} \end{productionlist} Import statements are executed in two steps: (1) find a module, and @@ -700,8 +705,10 @@ before the release in which the feature becomes standard. \begin{productionlist}[*] \production{future_statement} - {"from" "__future__" "import" feature ["as" name] ("," feature ["as" name])*} - \productioncont{| "from" "__future__" "import" "(" feature ["as" name] ("," feature ["as" name])* [","] ")"} + {"from" "__future__" "import" feature ["as" name]} + \productioncont{ ("," feature ["as" name])*} + \productioncont{| "from" "__future__" "import" "(" feature ["as" name]} + \productioncont{ ("," feature ["as" name])* [","] ")"} \production{feature}{identifier} \production{name}{identifier} \end{productionlist} @@ -718,9 +725,10 @@ lines that can appear before a future statement are: \end{itemize} -The features recognized by Python 2.3 are \samp{generators}, -\samp{division} and \samp{nested_scopes}. \samp{generators} and -\samp{nested_scopes} are redundant in 2.3 because they are always +The features recognized by Python 2.5 are \samp{absolute_import}, +\samp{division}, \samp{generators}, \samp{nested_scopes} and +\samp{with_statement}. \samp{generators} and \samp{nested_scopes} +are redundant in Python version 2.3 and above because they are always enabled. A future statement is recognized and treated specially at compile diff --git a/Doc/ref/ref7.tex b/Doc/ref/ref7.tex index 6bc0b08..02f96a4 100644 --- a/Doc/ref/ref7.tex +++ b/Doc/ref/ref7.tex @@ -313,7 +313,7 @@ be encapsulated for convenient reuse. \begin{productionlist} \production{with_stmt} - {"with" \token{expression} ["as" target] ":" \token{suite}} + {"with" \token{expression} ["as" \token{target}] ":" \token{suite}} \end{productionlist} The execution of the \keyword{with} statement proceeds as follows: |