summaryrefslogtreecommitdiffstats
path: root/Doc/ref/ref3.tex
diff options
context:
space:
mode:
authorGuido van Rossum <guido@python.org>1994-08-01 12:22:53 (GMT)
committerGuido van Rossum <guido@python.org>1994-08-01 12:22:53 (GMT)
commit6938f06047a6d2170523cfc3ab8e797bae0a6c05 (patch)
tree1da91a88f322e85f03c8eedfc191f610209dfb4e /Doc/ref/ref3.tex
parentab3a2504b97d5131779f400717dc491919783dd0 (diff)
downloadcpython-6938f06047a6d2170523cfc3ab8e797bae0a6c05.zip
cpython-6938f06047a6d2170523cfc3ab8e797bae0a6c05.tar.gz
cpython-6938f06047a6d2170523cfc3ab8e797bae0a6c05.tar.bz2
Merge alpha100 branch back to main trunk
Diffstat (limited to 'Doc/ref/ref3.tex')
-rw-r--r--Doc/ref/ref3.tex220
1 files changed, 112 insertions, 108 deletions
diff --git a/Doc/ref/ref3.tex b/Doc/ref/ref3.tex
index 41ce234..5f9a0d8 100644
--- a/Doc/ref/ref3.tex
+++ b/Doc/ref/ref3.tex
@@ -44,7 +44,7 @@ Some objects contain references to ``external'' resources such as open
files or windows. It is understood that these resources are freed
when the object is garbage-collected, but since garbage collection is
not guaranteed to happen, such objects also provide an explicit way to
-release the external resource, usually a \verb\close\ method.
+release the external resource, usually a \verb@close@ method.
Programs are strongly recommended to always explicitly close such
objects.
@@ -69,8 +69,8 @@ objects this is not allowed. E.g. after
a = 1; b = 1; c = []; d = []
\end{verbatim}
-\verb\a\ and \verb\b\ may or may not refer to the same object with the
-value one, depending on the implementation, but \verb\c\ and \verb\d\
+\verb@a@ and \verb@b@ may or may not refer to the same object with the
+value one, depending on the implementation, but \verb@c@ and \verb@d@
are guaranteed to refer to two different, unique, newly created empty
lists.
@@ -90,9 +90,9 @@ Some of the type descriptions below contain a paragraph listing
`special attributes'. These are attributes that provide access to the
implementation and are not intended for general use. Their definition
may change in the future. There are also some `generic' special
-attributes, not listed with the individual objects: \verb\__methods__\
+attributes, not listed with the individual objects: \verb@__methods__@
is a list of the method names of a built-in object, if it has any;
-\verb\__members__\ is a list of the data attribute names of a built-in
+\verb@__members__@ is a list of the data attribute names of a built-in
object, if it has any.
\index{attribute}
\indexii{special}{attribute}
@@ -104,7 +104,7 @@ object, if it has any.
\item[None]
This type has a single value. There is a single object with this value.
-This object is accessed through the built-in name \verb\None\.
+This object is accessed through the built-in name \verb@None@.
It is returned from functions that don't explicitly return an object.
\ttindex{None}
\obindex{None@{\tt None}}
@@ -134,7 +134,7 @@ These represent numbers in the range $-2^{31}$ through $2^{31}-1$.
(The range may be larger on machines with a larger natural word
size, but not smaller.)
When the result of an operation falls outside this range, the
-exception \verb\OverflowError\ is raised.
+exception \verb@OverflowError@ is raised.
For the purpose of shift and mask operations, integers are assumed to
have a binary, 2's complement notation using 32 or more bits, and
hiding no bits from the user (i.e., all $2^{32}$ different bit
@@ -172,17 +172,17 @@ C implementation for the accepted range and handling of overflow.
\item[Sequences]
These represent finite ordered sets indexed by natural numbers.
-The built-in function \verb\len()\ returns the number of elements
+The built-in function \verb@len()@ returns the number of elements
of a sequence. When this number is $n$, the index set contains
-the numbers $0, 1, \ldots, n-1$. Element \verb\i\ of sequence
-\verb\a\ is selected by \verb\a[i]\.
+the numbers $0, 1, \ldots, n-1$. Element \verb@i@ of sequence
+\verb@a@ is selected by \verb@a[i]@.
\obindex{seqence}
\bifuncindex{len}
\index{index operation}
\index{item selection}
\index{subscription}
-Sequences also support slicing: \verb\a[i:j]\ selects all elements
+Sequences also support slicing: \verb@a[i:j]@ selects all elements
with index $k$ such that $i <= k < j$. When used as an expression,
a slice is a sequence of the same type --- this implies that the
index set is renumbered so that it starts at 0 again.
@@ -209,7 +209,7 @@ The following types are immutable sequences:
The elements of a string are characters. There is no separate
character type; a character is represented by a string of one element.
Characters represent (at least) 8-bit bytes. The built-in
-functions \verb\chr()\ and \verb\ord()\ convert between characters
+functions \verb@chr()@ and \verb@ord()@ convert between characters
and nonnegative integers representing the byte values.
Bytes with the values 0-127 represent the corresponding ASCII values.
The string data type is also used to represent arrays of bytes, e.g.
@@ -223,7 +223,7 @@ to hold data read from a file.
(On systems whose native character set is not ASCII, strings may use
EBCDIC in their internal representation, provided the functions
-\verb\chr()\ and \verb\ord()\ implement a mapping between ASCII and
+\verb@chr()@ and \verb@ord()@ implement a mapping between ASCII and
EBCDIC, and string comparison preserves the ASCII order.
Or perhaps someone can propose a better rule?)
\index{ASCII}
@@ -250,7 +250,7 @@ parentheses.
\item[Mutable sequences]
Mutable sequences can be changed after they are created. The
subscription and slicing notations can be used as the target of
-assignment and \verb\del\ (delete) statements.
+assignment and \verb@del@ (delete) statements.
\obindex{mutable sequece}
\obindex{mutable}
\indexii{assignment}{statement}
@@ -276,10 +276,10 @@ or 1.)
\item[Mapping types]
These represent finite sets of objects indexed by arbitrary index sets.
-The subscript notation \verb\a[k]\ selects the element indexed
-by \verb\k\ from the mapping \verb\a\; this can be used in
-expressions and as the target of assignments or \verb\del\ statements.
-The built-in function \verb\len()\ returns the number of elements
+The subscript notation \verb@a[k]@ selects the element indexed
+by \verb@k@ from the mapping \verb@a@; this can be used in
+expressions and as the target of assignments or \verb@del@ statements.
+The built-in function \verb@len()@ returns the number of elements
in a mapping.
\bifuncindex{len}
\index{subscription}
@@ -299,7 +299,7 @@ Numeric types used for keys obey the normal rules for numeric
comparison: if two numbers compare equal (e.g. 1 and 1.0) then they
can be used interchangeably to index the same dictionary entry.
-Dictionaries are mutable; they are created by the \verb\{...}\
+Dictionaries are mutable; they are created by the \verb@{...}@
notation (see section \ref{dict}).
\obindex{dictionary}
\obindex{mutable}
@@ -308,7 +308,7 @@ notation (see section \ref{dict}).
\item[Callable types]
These are the types to which the function call (invocation) operation,
-written as \verb\function(argument, argument, ...)\, can be applied:
+written as \verb@function(argument, argument, ...)@, can be applied:
\indexii{function}{call}
\index{invocation}
\indexii{function}{argument}
@@ -325,8 +325,8 @@ parameter list.
\obindex{function}
\obindex{user-defined function}
-Special read-only attributes: \verb\func_code\ is the code object
-representing the compiled function body, and \verb\func_globals\ is (a
+Special read-only attributes: \verb@func_code@ is the code object
+representing the compiled function body, and \verb@func_globals@ is (a
reference to) the dictionary that holds the function's global
variables --- it implements the global name space of the module in
which the function was defined.
@@ -346,14 +346,14 @@ shifted one to the right.
\indexii{user-defined}{method}
\index{object closure}
-Special read-only attributes: \verb\im_self\ is the class instance
-object, \verb\im_func\ is the function object.
+Special read-only attributes: \verb@im_self@ is the class instance
+object, \verb@im_func@ is the function object.
\ttindex{im_func}
\ttindex{im_self}
\item[Built-in functions]
A built-in function object is a wrapper around a C function. Examples
-of built-in functions are \verb\len\ and \verb\math.sin\. There
+of built-in functions are \verb@len@ and \verb@math.sin@. There
are no special attributes. The number and type of the arguments are
determined by the C function.
\obindex{built-in function}
@@ -363,18 +363,20 @@ determined by the C function.
\item[Built-in methods]
This is really a different disguise of a built-in function, this time
containing an object passed to the C function as an implicit extra
-argument. An example of a built-in method is \verb\list.append\ if
-\verb\list\ is a list object.
+argument. An example of a built-in method is \verb@list.append@ if
+\verb@list@ is a list object.
\obindex{built-in method}
\obindex{method}
\indexii{built-in}{method}
\item[Classes]
Class objects are described below. When a class object is called as a
-parameterless function, a new class instance (also described below) is
-created and returned. The class's initialization function is not
-called --- this is the responsibility of the caller. It is illegal to
-call a class object with one or more arguments.
+function, a new class instance (also described below) is created and
+returned. This implies a call to the class's \verb@__init__@ method
+if it has one. Any arguments are passed on to the \verb@__init__@
+method -- if there is \verb@__init__@ method, the class must be called
+without arguments.
+\ttindex{__init__}
\obindex{class}
\obindex{class instance}
\obindex{instance}
@@ -383,10 +385,10 @@ call a class object with one or more arguments.
\end{description}
\item[Modules]
-Modules are imported by the \verb\import\ statement (see section
+Modules are imported by the \verb@import@ statement (see section
\ref{import}). A module object is a container for a module's name
space, which is a dictionary (the same dictionary as referenced by the
-\verb\func_globals\ attribute of functions defined in the module).
+\verb@func_globals@ attribute of functions defined in the module).
Module attribute references are translated to lookups in this
dictionary. A module object does not contain the code object used to
initialize the module (since it isn't needed once the initialization
@@ -396,8 +398,8 @@ is done).
Attribute assignment update the module's name space dictionary.
-Special read-only attributes: \verb\__dict__\ yields the module's name
-space as a dictionary object; \verb\__name__\ yields the module's name
+Special read-only attributes: \verb@__dict__@ yields the module's name
+space as a dictionary object; \verb@__name__@ yields the module's name
as a string object.
\ttindex{__dict__}
\ttindex{__name__}
@@ -423,12 +425,12 @@ Class attribute assignments update the class's dictionary, never the
dictionary of a base class.
\indexiii{class}{attribute}{assignment}
-A class can be called as a parameterless function to yield a class
-instance (see above).
+A class can be called as a function to yield a class instance (see
+above).
\indexii{class object}{call}
-Special read-only attributes: \verb\__dict__\ yields the dictionary
-containing the class's name space; \verb\__bases__\ yields a tuple
+Special read-only attributes: \verb@__dict__@ yields the dictionary
+containing the class's name space; \verb@__bases__@ yields a tuple
(possibly empty or a singleton) containing the base classes, in the
order of their occurrence in the base class list.
\ttindex{__dict__}
@@ -436,7 +438,7 @@ order of their occurrence in the base class list.
\item[Class instances]
A class instance is created by calling a class object as a
-parameterless function. A class instance has a dictionary in which
+function. A class instance has a dictionary in which
attribute references are searched. When an attribute is not found
there, and the instance's class has an attribute by that name, and
that class attribute is a user-defined function (and in no other
@@ -457,17 +459,17 @@ section \ref{specialnames}.
\obindex{sequence}
\obindex{mapping}
-Special read-only attributes: \verb\__dict__\ yields the attribute
-dictionary; \verb\__class__\ yields the instance's class.
+Special read-only attributes: \verb@__dict__@ yields the attribute
+dictionary; \verb@__class__@ yields the instance's class.
\ttindex{__dict__}
\ttindex{__class__}
\item[Files]
A file object represents an open file. (It is a wrapper around a C
{\tt stdio} file pointer.) File objects are created by the
-\verb\open()\ built-in function, and also by \verb\posix.popen()\ and
-the \verb\makefile\ method of socket objects. \verb\sys.stdin\,
-\verb\sys.stdout\ and \verb\sys.stderr\ are file objects corresponding
+\verb@open()@ built-in function, and also by \verb@posix.popen()@ and
+the \verb@makefile@ method of socket objects. \verb@sys.stdin@,
+\verb@sys.stdout@ and \verb@sys.stderr@ are file objects corresponding
the the interpreter's standard input, output and error streams.
See the Python Library Reference for methods of file objects and other
details.
@@ -500,12 +502,12 @@ was defined) which a code object contains no context. There is no way
to execute a bare code object.
\obindex{code}
-Special read-only attributes: \verb\co_code\ is a string representing
-the sequence of instructions; \verb\co_consts\ is a list of literals
-used by the code; \verb\co_names\ is a list of names (strings) used by
-the code; \verb\co_filename\ is the filename from which the code was
+Special read-only attributes: \verb@co_code@ is a string representing
+the sequence of instructions; \verb@co_consts@ is a list of literals
+used by the code; \verb@co_names@ is a list of names (strings) used by
+the code; \verb@co_filename@ is the filename from which the code was
compiled. (To find out the line numbers, you would have to decode the
-instructions; the standard library module \verb\dis\ contains an
+instructions; the standard library module \verb@dis@ contains an
example of how to do this.)
\ttindex{co_code}
\ttindex{co_consts}
@@ -517,12 +519,12 @@ Frame objects represent execution frames. They may occur in traceback
objects (see below).
\obindex{frame}
-Special read-only attributes: \verb\f_back\ is to the previous
-stack frame (towards the caller), or \verb\None\ if this is the bottom
-stack frame; \verb\f_code\ is the code object being executed in this
-frame; \verb\f_globals\ is the dictionary used to look up global
-variables; \verb\f_locals\ is used for local variables;
-\verb\f_lineno\ gives the line number and \verb\f_lasti\ gives the
+Special read-only attributes: \verb@f_back@ is to the previous
+stack frame (towards the caller), or \verb@None@ if this is the bottom
+stack frame; \verb@f_code@ is the code object being executed in this
+frame; \verb@f_globals@ is the dictionary used to look up global
+variables; \verb@f_locals@ is used for local variables;
+\verb@f_lineno@ gives the line number and \verb@f_lasti@ gives the
precise instruction (this is an index into the instruction string of
the code object).
\ttindex{f_back}
@@ -539,11 +541,11 @@ for an exception handler unwinds the execution stack, at each unwound
level a traceback object is inserted in front of the current
traceback. When an exception handler is entered
(see also section \ref{try}), the stack trace is
-made available to the program as \verb\sys.exc_traceback\. When the
+made available to the program as \verb@sys.exc_traceback@. When the
program contains no suitable handler, the stack trace is written
(nicely formatted) to the standard error stream; if the interpreter is
interactive, it is also made available to the user as
-\verb\sys.last_traceback\.
+\verb@sys.last_traceback@.
\obindex{traceback}
\indexii{stack}{trace}
\indexii{exception}{handler}
@@ -553,15 +555,15 @@ interactive, it is also made available to the user as
\ttindex{sys.exc_traceback}
\ttindex{sys.last_traceback}
-Special read-only attributes: \verb\tb_next\ is the next level in the
+Special read-only attributes: \verb@tb_next@ is the next level in the
stack trace (towards the frame where the exception occurred), or
-\verb\None\ if there is no next level; \verb\tb_frame\ points to the
-execution frame of the current level; \verb\tb_lineno\ gives the line
-number where the exception occurred; \verb\tb_lasti\ indicates the
+\verb@None@ if there is no next level; \verb@tb_frame@ points to the
+execution frame of the current level; \verb@tb_lineno@ gives the line
+number where the exception occurred; \verb@tb_lasti@ indicates the
precise instruction. The line number and last instruction in the
traceback may differ from the line number of its frame object if the
-exception occurred in a \verb\try\ statement with no matching
-\verb\except\ clause or with a \verb\finally\ clause.
+exception occurred in a \verb@try@ statement with no matching
+\verb@except@ clause or with a \verb@finally@ clause.
\ttindex{tb_next}
\ttindex{tb_frame}
\ttindex{tb_lineno}
@@ -578,17 +580,19 @@ exception occurred in a \verb\try\ statement with no matching
A class can implement certain operations that are invoked by special
syntax (such as subscription or arithmetic operations) by defining
methods with special names. For instance, if a class defines a
-method named \verb\__getitem__\, and \verb\x\ is an instance of this
-class, then \verb\x[i]\ is equivalent to \verb\x.__getitem__(i)\.
-(The reverse is not true --- if \verb\x\ is a list object,
-\verb\x.__getitem__(i)\ is not equivalent to \verb\x[i]\.)
+method named \verb@__getitem__@, and \verb@x@ is an instance of this
+class, then \verb@x[i]@ is equivalent to \verb@x.__getitem__(i)@.
+(The reverse is not true --- if \verb@x@ is a list object,
+\verb@x.__getitem__(i)@ is not equivalent to \verb@x[i]@.)
-Except for \verb\__repr__\, \verb\__str__\ and \verb\__cmp__\,
+Except for \verb@__repr__@, \verb@__str__@ and \verb@__cmp__@,
attempts to execute an
operation raise an exception when no appropriate method is defined.
-For \verb\__repr__\ and \verb\__cmp__\, the traditional
-interpretations are used in this case.
-For \verb\__str__\, the \verb\__repr__\ method is used.
+For \verb@__repr__@, the default is to return a string describing the
+object's class and address.
+For \verb@__cmp__@, the default is to compare instances based on their
+address.
+For \verb@__str__@, the default is to use \verb@__repr__@.
\subsection{Special methods for any type}
@@ -614,17 +618,17 @@ reference is deleted. Also note that it is not guaranteed that
the interpreter exits.
\item[\tt __repr__(self)]
-Called by the \verb\repr()\ built-in function and by conversions
+Called by the \verb@repr()@ built-in function and by conversions
(reverse quotes) to compute the string representation of an object.
\item[\tt __str__(self)]
-Called by the \verb\str()\ built-in function and by the \verb\print\
+Called by the \verb@str()@ built-in function and by the \verb@print@
statement compute the string representation of an object.
\item[\tt __cmp__(self, other)]
Called by all comparison operations. Should return -1 if
-\verb\self < other\, 0 if \verb\self == other\, +1 if
-\verb\self > other\. If no \code{__cmp__} operation is defined, class
+\verb@self < other@, 0 if \verb@self == other@, +1 if
+\verb@self > other@. If no \code{__cmp__} operation is defined, class
instances are compared by object identity (``address'').
(Implementation note: due to limitations in the interpreter,
exceptions raised by comparisons are ignored, and the objects will be
@@ -654,23 +658,23 @@ key's hash value is a constant.
\begin{description}
\item[\tt __len__(self)]
-Called to implement the built-in function \verb\len()\. Should return
-the length of the object, an integer \verb\>=\ 0. Also, an object
-whose \verb\__len__()\ method returns 0 is considered to be false in a
+Called to implement the built-in function \verb@len()@. Should return
+the length of the object, an integer \verb@>=@ 0. Also, an object
+whose \verb@__len__()@ method returns 0 is considered to be false in a
Boolean context.
\item[\tt __getitem__(self, key)]
-Called to implement evaluation of \verb\self[key]\. Note that the
+Called to implement evaluation of \verb@self[key]@. Note that the
special interpretation of negative keys (if the class wishes to
-emulate a sequence type) is up to the \verb\__getitem__\ method.
+emulate a sequence type) is up to the \verb@__getitem__@ method.
\item[\tt __setitem__(self, key, value)]
-Called to implement assignment to \verb\self[key]\. Same note as for
-\verb\__getitem__\.
+Called to implement assignment to \verb@self[key]@. Same note as for
+\verb@__getitem__@.
\item[\tt __delitem__(self, key)]
-Called to implement deletion of \verb\self[key]\. Same note as for
-\verb\__getitem__\.
+Called to implement deletion of \verb@self[key]@. Same note as for
+\verb@__getitem__@.
\end{description}
@@ -680,19 +684,19 @@ Called to implement deletion of \verb\self[key]\. Same note as for
\begin{description}
\item[\tt __getslice__(self, i, j)]
-Called to implement evaluation of \verb\self[i:j]\. Note that missing
-\verb\i\ or \verb\j\ are replaced by 0 or \verb\len(self)\,
-respectively, and \verb\len(self)\ has been added (once) to originally
-negative \verb\i\ or \verb\j\ by the time this function is called
-(unlike for \verb\__getitem__\).
+Called to implement evaluation of \verb@self[i:j]@. Note that missing
+\verb@i@ or \verb@j@ are replaced by 0 or \verb@len(self)@,
+respectively, and \verb@len(self)@ has been added (once) to originally
+negative \verb@i@ or \verb@j@ by the time this function is called
+(unlike for \verb@__getitem__@).
\item[\tt __setslice__(self, i, j, sequence)]
-Called to implement assignment to \verb\self[i:j]\. Same notes as for
-\verb\__getslice__\.
+Called to implement assignment to \verb@self[i:j]@. Same notes as for
+\verb@__getslice__@.
\item[\tt __delslice__(self, i, j)]
-Called to implement deletion of \verb\self[i:j]\. Same notes as for
-\verb\__getslice__\.
+Called to implement deletion of \verb@self[i:j]@. Same notes as for
+\verb@__getslice__@.
\end{description}
@@ -713,20 +717,20 @@ Called to implement deletion of \verb\self[i:j]\. Same notes as for
\item[\tt __and__(self, other)]\itemjoin
\item[\tt __xor__(self, other)]\itemjoin
\item[\tt __or__(self, other)]\itembreak
-Called to implement the binary arithmetic operations (\verb\+\,
-\verb\-\, \verb\*\, \verb\/\, \verb\%\, \verb\divmod()\, \verb\pow()\,
-\verb\<<\, \verb\>>\, \verb\&\, \verb\^\, \verb\|\).
+Called to implement the binary arithmetic operations (\verb@+@,
+\verb@-@, \verb@*@, \verb@/@, \verb@%@, \verb@divmod()@, \verb@pow()@,
+\verb@<<@, \verb@>>@, \verb@&@, \verb@^@, \verb@|@).
\item[\tt __neg__(self)]\itemjoin
\item[\tt __pos__(self)]\itemjoin
\item[\tt __abs__(self)]\itemjoin
\item[\tt __invert__(self)]\itembreak
-Called to implement the unary arithmetic operations (\verb\-\, \verb\+\,
-\verb\abs()\ and \verb\~\).
+Called to implement the unary arithmetic operations (\verb@-@, \verb@+@,
+\verb@abs()@ and \verb@~@).
\item[\tt __nonzero__(self)]
Called to implement boolean testing; should return 0 or 1. An
-alternative name for this method is \verb\__len__\.
+alternative name for this method is \verb@__len__@.
\item[\tt __coerce__(self, other)]
Called to implement ``mixed-mode'' numeric arithmetic. Should either
@@ -737,11 +741,11 @@ interpreter will also ask the other object to attempt a coercion (but
sometimes, if the implementation of the other type cannot be changed,
it is useful to do the conversion to the other type here).
-Note that this method is not called to coerce the arguments to \verb\+\
-and \verb\*\, because these are also used to implement sequence
+Note that this method is not called to coerce the arguments to \verb@+@
+and \verb@*@, because these are also used to implement sequence
concatenation and repetition, respectively. Also note that, for the
-same reason, in \verb\n*x\, where \verb\n\ is a built-in number and
-\verb\x\ is an instance, a call to \verb\x.__mul__(n)\ is made.%
+same reason, in \verb@n*x@, where \verb@n@ is a built-in number and
+\verb@x@ is an instance, a call to \verb@x.__mul__(n)@ is made.%
\footnote{The interpreter should really distinguish between
user-defined classes implementing sequences, mappings or numbers, but
currently it doesn't --- hence this strange exception.}
@@ -749,12 +753,12 @@ currently it doesn't --- hence this strange exception.}
\item[\tt __int__(self)]\itemjoin
\item[\tt __long__(self)]\itemjoin
\item[\tt __float__(self)]\itembreak
-Called to implement the built-in functions \verb\int()\, \verb\long()\
-and \verb\float()\. Should return a value of the appropriate type.
+Called to implement the built-in functions \verb@int()@, \verb@long()@
+and \verb@float()@. Should return a value of the appropriate type.
\item[\tt __oct__(self)]\itemjoin
\item[\tt __hex__(self)]\itembreak
-Called to implement the built-in functions \verb\oct()\ and
-\verb\hex()\. Should return a string value.
+Called to implement the built-in functions \verb@oct()@ and
+\verb@hex()@. Should return a string value.
\end{description}