[Python-checkins] python/dist/src/Doc/lib libstdtypes.tex,1.97,1.98
holdenweb@users.sourceforge.net
holdenweb@users.sourceforge.net
2002年6月14日 02:16:42 -0700
Update of /cvsroot/python/python/dist/src/Doc/lib
In directory usw-pr-cvs1:/tmp/cvs-serv29235
Modified Files:
libstdtypes.tex
Log Message:
Make a start at describing the results of class/type unification
in the type documentation.
Index: libstdtypes.tex
===================================================================
RCS file: /cvsroot/python/python/dist/src/Doc/lib/libstdtypes.tex,v
retrieving revision 1.97
retrieving revision 1.98
diff -C2 -d -r1.97 -r1.98
*** libstdtypes.tex 14 Jun 2002 00:27:13 -0000 1.97
--- libstdtypes.tex 14 Jun 2002 09:16:40 -0000 1.98
***************
*** 2,7 ****
The following sections describe the standard types that are built into
! the interpreter. These are the numeric types, sequence types, and
! several others, including types themselves.
\indexii{built-in}{types}
--- 2,14 ----
The following sections describe the standard types that are built into
! the interpreter. Historically, Python's built-in types have differed
! from user-defined types because it was not possible to use the built-in
! types as the basis for object-oriented inheritance. With the 2.2
! release this situation has started to change, although the intended
! unification of user-defined and built-in types is as yet far from
! complete.
!
! The principal built-in types are numerics, sequences, mappings, files
! classes, instances and exceptions.
\indexii{built-in}{types}
***************
*** 13,17 ****
! \subsection{Truth Value Testing \label{truth}}
Any object can be tested for truth value, for use in an \keyword{if} or
--- 20,24 ----
! \subsection{Truth Value Testing} \label{truth}
Any object can be tested for truth value, for use in an \keyword{if} or
***************
*** 129,136 ****
\item[(1)]
\code{<>} and \code{!=} are alternate spellings for the same operator.
- (I couldn't choose between \ABC{} and C! :-)
- \index{ABC language@\ABC{} language}
- \index{language!ABC@\ABC}
- \indexii{C}{language}
\code{!=} is the preferred spelling; \code{<>} is obsolescent.
--- 136,139 ----
***************
*** 143,147 ****
degenerate notion of comparison where any two objects of that type are
unequal. Again, such objects are ordered arbitrarily but
! consistently.
\indexii{object}{numeric}
\indexii{objects}{comparing}
--- 146,152 ----
degenerate notion of comparison where any two objects of that type are
unequal. Again, such objects are ordered arbitrarily but
! consistently. The \code{<}, \code{<=}, \code{>} and \code{>=}
! operators will raise a \exception{TypeError} exception when any operand
! is a complex number.
\indexii{object}{numeric}
\indexii{objects}{comparing}
***************
*** 182,186 ****
\indexii{C}{language}
! Complex numbers have a real and imaginary part, which are both
implemented using \ctype{double} in C. To extract these parts from
a complex number \var{z}, use \code{\var{z}.real} and \code{\var{z}.imag}.
--- 187,191 ----
\indexii{C}{language}
! Complex numbers have a real and imaginary part, which are each
implemented using \ctype{double} in C. To extract these parts from
a complex number \var{z}, use \code{\var{z}.real} and \code{\var{z}.imag}.
***************
*** 188,197 ****
Numbers are created by numeric literals or as the result of built-in
functions and operators. Unadorned integer literals (including hex
! and octal numbers) yield plain integers. Integer literals with an
\character{L} or \character{l} suffix yield long integers
(\character{L} is preferred because \samp{1l} looks too much like
eleven!). Numeric literals containing a decimal point or an exponent
sign yield floating point numbers. Appending \character{j} or
! \character{J} to a numeric literal yields a complex number.
\indexii{numeric}{literals}
\indexii{integer}{literals}
--- 193,206 ----
Numbers are created by numeric literals or as the result of built-in
functions and operators. Unadorned integer literals (including hex
! and octal numbers) yield plain integers unless the value they denote
! is too large to be represented as a plain integer, in which case
! they yield a long integer. Integer literals with an
\character{L} or \character{l} suffix yield long integers
(\character{L} is preferred because \samp{1l} looks too much like
eleven!). Numeric literals containing a decimal point or an exponent
sign yield floating point numbers. Appending \character{j} or
! \character{J} to a numeric literal yields a complex number with a
! zero real part. A complex numeric literal is the sum of a real and
! an imaginary part.
\indexii{numeric}{literals}
\indexii{integer}{literals}
***************
*** 204,216 ****
Python fully supports mixed arithmetic: when a binary arithmetic
operator has operands of different numeric types, the operand with the
! ``smaller'' type is converted to that of the other, where plain
! integer is smaller than long integer is smaller than floating point is
! smaller than complex.
Comparisons between numbers of mixed type use the same rule.\footnote{
As a consequence, the list \code{[1, 2]} is considered equal
! to \code{[1.0, 2.0]}, and similar for tuples.
! } The functions \function{int()}, \function{long()}, \function{float()},
and \function{complex()} can be used
! to coerce numbers to a specific type.
\index{arithmetic}
\bifuncindex{int}
--- 213,225 ----
Python fully supports mixed arithmetic: when a binary arithmetic
operator has operands of different numeric types, the operand with the
! ``narrower'' type is widened to that of the other, where plain
! integer is narrower than long integer is narrower than floating point is
! narrower than complex.
Comparisons between numbers of mixed type use the same rule.\footnote{
As a consequence, the list \code{[1, 2]} is considered equal
! to \code{[1.0, 2.0]}, and similarly for tuples.
! } The constructors \function{int()}, \function{long()}, \function{float()},
and \function{complex()} can be used
! to produce numbers of a specific type.
\index{arithmetic}
\bifuncindex{int}
***************
*** 219,224 ****
\bifuncindex{complex}
! All numeric types (except complex) support the following operations,
! sorted by ascending priority (operations in the same box have the same
priority; all numeric operations have a higher priority than
comparison operations):
--- 228,233 ----
\bifuncindex{complex}
! All numeric types support the following operations, sorted by
! ascending priority (operations in the same box have the same
priority; all numeric operations have a higher priority than
comparison operations):
***************
*** 230,234 ****
\lineiii{\var{x} * \var{y}}{product of \var{x} and \var{y}}{}
\lineiii{\var{x} / \var{y}}{quotient of \var{x} and \var{y}}{(1)}
! \lineiii{\var{x} \%{} \var{y}}{remainder of \code{\var{x} / \var{y}}}{(4)}
\hline
\lineiii{-\var{x}}{\var{x} negated}{}
--- 239,243 ----
\lineiii{\var{x} * \var{y}}{product of \var{x} and \var{y}}{}
\lineiii{\var{x} / \var{y}}{quotient of \var{x} and \var{y}}{(1)}
! \lineiii{\var{x} \%{} \var{y}}{remainder of \code{\var{x} / \var{y}}}{}
\hline
\lineiii{-\var{x}}{\var{x} negated}{}
***************
*** 241,245 ****
\lineiii{complex(\var{re},\var{im})}{a complex number with real part \var{re}, imaginary part \var{im}. \var{im} defaults to zero.}{}
\lineiii{\var{c}.conjugate()}{conjugate of the complex number \var{c}}{}
! \lineiii{divmod(\var{x}, \var{y})}{the pair \code{(\var{x} / \var{y}, \var{x} \%{} \var{y})}}{(3)(4)}
\lineiii{pow(\var{x}, \var{y})}{\var{x} to the power \var{y}}{}
\lineiii{\var{x} ** \var{y}}{\var{x} to the power \var{y}}{}
--- 250,254 ----
\lineiii{complex(\var{re},\var{im})}{a complex number with real part \var{re}, imaginary part \var{im}. \var{im} defaults to zero.}{}
\lineiii{\var{c}.conjugate()}{conjugate of the complex number \var{c}}{}
! \lineiii{divmod(\var{x}, \var{y})}{the pair \code{(\var{x} / \var{y}, \var{x} \%{} \var{y})}}{(3)}
\lineiii{pow(\var{x}, \var{y})}{\var{x} to the power \var{y}}{}
\lineiii{\var{x} ** \var{y}}{\var{x} to the power \var{y}}{}
***************
*** 274,283 ****
description.
- \item[(4)]
- Complex floor division operator, modulo operator, and \function{divmod()}.
-
- \deprecated{2.3}{Instead convert to float using \function{abs()}
- if appropriate.}
-
\end{description}
% XXXJH exceptions: overflow (when? what operations?) zerodivision
--- 283,286 ----
***************
*** 381,385 ****
tuples, buffers, and xrange objects.
! Strings literals are written in single or double quotes:
\code{'xyzzy'}, \code{"frobozz"}. See chapter 2 of the
\citetitle[../ref/strings.html]{Python Reference Manual} for more about
--- 384,388 ----
tuples, buffers, and xrange objects.
! String literals are written in single or double quotes:
\code{'xyzzy'}, \code{"frobozz"}. See chapter 2 of the
\citetitle[../ref/strings.html]{Python Reference Manual} for more about
***************
*** 400,414 ****
Buffer objects are not directly supported by Python syntax, but can be
created by calling the builtin function
! \function{buffer()}.\bifuncindex{buffer} They support concatenation
! and repetition, but the result is a new string object rather than a
! new buffer object.
\obindex{buffer}
Xrange objects are similar to buffers in that there is no specific
! syntax to create them, but they are created using the
! \function{xrange()} function.\bifuncindex{xrange} They don't support
! slicing, concatenation, or repetition, and using \keyword{in},
! \keyword{not} \keyword{in}, \function{min()} or \function{max()} on
! them is inefficient.
\obindex{xrange}
--- 403,415 ----
Buffer objects are not directly supported by Python syntax, but can be
created by calling the builtin function
! \function{buffer()}.\bifuncindex{buffer}. They don't support
! concatenation or repetition.
\obindex{buffer}
Xrange objects are similar to buffers in that there is no specific
! syntax to create them, but they are created using the \function{xrange()}
! function.\bifuncindex{xrange} They don't support slicing,
! concatenation or repetition, and using \code{in}, \code{not in},
! \function{min()} or \function{max()} on them is inefficient.
\obindex{xrange}
***************
*** 434,438 ****
\lineiii{\var{s}[\var{i}]}{\var{i}'th item of \var{s}, origin 0}{(2)}
\lineiii{\var{s}[\var{i}:\var{j}]}{slice of \var{s} from \var{i} to \var{j}}{(2), (3)}
- \lineiii{\var{s}[\var{i}:\var{j}:\var{k}]}{slice of \var{s} from \var{i} to \var{j} with step \var{k}}{(2), (4)}
\hline
\lineiii{len(\var{s})}{length of \var{s}}{}
--- 435,438 ----
***************
*** 448,452 ****
\indexii{subscript}{operation}
\indexii{slice}{operation}
- \indexii{extended slice}{operation}
\opindex{in}
\opindex{not in}
--- 448,451 ----
***************
*** 495,507 ****
use \code{0}. If \var{j} is omitted, use \code{len(\var{s})}. If
\var{i} is greater than or equal to \var{j}, the slice is empty.
-
- \item[(4)] The slice of \var{s} from \var{i} to \var{j} with step \var{k}
- is defined as the sequence of items with index \code{\var{x} =
- \var{i} + \var{n}*\var{k}} such that \var{n} \code{>=} \code{0} and
- \code{\var{i} <= \var{x} < \var{j}}. If \var{i} or \var{j} is
- greater than \code{len(\var{s})}, use \code{len(\var{s})}. If
- \var{i} or \var{j} are ommitted then they become ``end'' values
- (which end depends on the sign of \var{k}).
-
\end{description}
--- 494,497 ----
***************
*** 548,553 ****
\begin{methoddesc}[string]{endswith}{suffix\optional{, start\optional{, end}}}
! Return \code{True} if the string ends with the specified \var{suffix},
! otherwise return \code{False}. With optional \var{start}, test beginning at
that position. With optional \var{end}, stop comparing at that position.
\end{methoddesc}
--- 538,543 ----
\begin{methoddesc}[string]{endswith}{suffix\optional{, start\optional{, end}}}
! Return true if the string ends with the specified \var{suffix},
! otherwise return false. With optional \var{start}, test beginning at
that position. With optional \var{end}, stop comparing at that position.
\end{methoddesc}
***************
*** 679,684 ****
\begin{methoddesc}[string]{startswith}{prefix\optional{,
start\optional{, end}}}
! Return \code{True} if string starts with the \var{prefix}, otherwise
! return \code{False}. With optional \var{start}, test string beginning at
that position. With optional \var{end}, stop comparing string at that
position.
--- 669,674 ----
\begin{methoddesc}[string]{startswith}{prefix\optional{,
start\optional{, end}}}
! Return true if string starts with the \var{prefix}, otherwise
! return false. With optional \var{start}, test string beginning at
that position. With optional \var{end}, stop comparing string at that
position.
***************
*** 741,749 ****
\var{format} is a Unicode object, or if any of the objects being
converted using the \code{\%s} conversion are Unicode objects, the
! result will be a Unicode object as well.
If \var{format} requires a single argument, \var{values} may be a
! single non-tuple object. \footnote{A tuple object in this case should
! be a singleton.} Otherwise, \var{values} must be a tuple with
exactly the number of items specified by the format string, or a
single mapping object (for example, a dictionary).
--- 731,740 ----
\var{format} is a Unicode object, or if any of the objects being
converted using the \code{\%s} conversion are Unicode objects, the
! result will also be a Unicode object.
If \var{format} requires a single argument, \var{values} may be a
! single non-tuple object. \footnote{To format only a tuple you
! should therefore provide a singleton tuple whose only element
! is the tuple to be formatted.} Otherwise, \var{values} must be a tuple with
exactly the number of items specified by the format string, or a
single mapping object (for example, a dictionary).
***************
*** 755,760 ****
\item The \character{\%} character, which marks the start of the
specifier.
! \item Mapping key value (optional), consisting of an identifier in
! parentheses (for example, \code{(somename)}).
\item Conversion flags (optional), which affect the result of some
conversion types.
--- 746,751 ----
\item The \character{\%} character, which marks the start of the
specifier.
! \item Mapping key (optional), consisting of a parenthesised sequence
! of characters (for example, \code{(somename)}).
\item Conversion flags (optional), which affect the result of some
conversion types.
***************
*** 773,786 ****
\end{enumerate}
! If the right argument is a dictionary (or any kind of mapping), then
! the formats in the string \emph{must} have a parenthesized key into
that dictionary inserted immediately after the \character{\%}
! character, and each format formats the corresponding entry from the
mapping. For example:
\begin{verbatim}
! >>> count = 2
! >>> language = 'Python'
! >>> print '%(language)s has %(count)03d quote types.' % vars()
Python has 002 quote types.
\end{verbatim}
--- 764,776 ----
\end{enumerate}
! When the right argument is a dictionary (or other mapping type), then
! the formats in the string \emph{must} include a parenthesised mapping key into
that dictionary inserted immediately after the \character{\%}
! character. The mapping key selects the value to be formatted from the
mapping. For example:
\begin{verbatim}
! >>> print '%(language)s has %(#)03d quote types.' % \
! {'language': "Python", "#": 2}
Python has 002 quote types.
\end{verbatim}
***************
*** 871,877 ****
List objects support additional operations that allow in-place
modification of the object.
! These operations would be supported by other mutable sequence types
! (when added to the language) as well.
! Strings and tuples are immutable sequence types and such objects cannot
be modified once created.
The following operations are defined on mutable sequence types (where
--- 861,867 ----
List objects support additional operations that allow in-place
modification of the object.
! Other mutable sequence types (when added to the language) should
! also support these operations.
! Strings and tuples are immutable sequence types: such objects cannot
be modified once created.
The following operations are defined on mutable sequence types (where
***************
*** 887,913 ****
\lineiii{del \var{s}[\var{i}:\var{j}]}
{same as \code{\var{s}[\var{i}:\var{j}] = []}}{}
- \lineiii{\var{s}[\var{i}:\var{j}:\var{k}] = \var{t}}
- {the elements of \code{\var{s}[\var{i}:\var{j}:\var{k}]} are replaced by those of \var{t}}{(1)}
- \lineiii{del \var{s}[\var{i}:\var{j}:\var{k}]}
- {removes the elements of \code{\var{s}[\var{i}:\var{j}:\var{k}]} from the list}{}
\lineiii{\var{s}.append(\var{x})}
! {same as \code{\var{s}[len(\var{s}):len(\var{s})] = [\var{x}]}}{(2)}
\lineiii{\var{s}.extend(\var{x})}
! {same as \code{\var{s}[len(\var{s}):len(\var{s})] = \var{x}}}{(3)}
\lineiii{\var{s}.count(\var{x})}
{return number of \var{i}'s for which \code{\var{s}[\var{i}] == \var{x}}}{}
\lineiii{\var{s}.index(\var{x})}
! {return smallest \var{i} such that \code{\var{s}[\var{i}] == \var{x}}}{(4)}
\lineiii{\var{s}.insert(\var{i}, \var{x})}
{same as \code{\var{s}[\var{i}:\var{i}] = [\var{x}]}
! if \code{\var{i} >= 0}}{(5)}
\lineiii{\var{s}.pop(\optional{\var{i}})}
! {same as \code{\var{x} = \var{s}[\var{i}]; del \var{s}[\var{i}]; return \var{x}}}{(6)}
\lineiii{\var{s}.remove(\var{x})}
! {same as \code{del \var{s}[\var{s}.index(\var{x})]}}{(4)}
\lineiii{\var{s}.reverse()}
! {reverses the items of \var{s} in place}{(7)}
\lineiii{\var{s}.sort(\optional{\var{cmpfunc}})}
! {sort the items of \var{s} in place}{(7), (8)}
\end{tableiii}
\indexiv{operations on}{mutable}{sequence}{types}
--- 877,899 ----
\lineiii{del \var{s}[\var{i}:\var{j}]}
{same as \code{\var{s}[\var{i}:\var{j}] = []}}{}
\lineiii{\var{s}.append(\var{x})}
! {same as \code{\var{s}[len(\var{s}):len(\var{s})] = [\var{x}]}}{(1)}
\lineiii{\var{s}.extend(\var{x})}
! {same as \code{\var{s}[len(\var{s}):len(\var{s})] = \var{x}}}{(2)}
\lineiii{\var{s}.count(\var{x})}
{return number of \var{i}'s for which \code{\var{s}[\var{i}] == \var{x}}}{}
\lineiii{\var{s}.index(\var{x})}
! {return smallest \var{i} such that \code{\var{s}[\var{i}] == \var{x}}}{(3)}
\lineiii{\var{s}.insert(\var{i}, \var{x})}
{same as \code{\var{s}[\var{i}:\var{i}] = [\var{x}]}
! if \code{\var{i} >= 0}}{(4)}
\lineiii{\var{s}.pop(\optional{\var{i}})}
! {same as \code{\var{x} = \var{s}[\var{i}]; del \var{s}[\var{i}]; return \var{x}}}{(5)}
\lineiii{\var{s}.remove(\var{x})}
! {same as \code{del \var{s}[\var{s}.index(\var{x})]}}{(3)}
\lineiii{\var{s}.reverse()}
! {reverses the items of \var{s} in place}{(6)}
\lineiii{\var{s}.sort(\optional{\var{cmpfunc}})}
! {sort the items of \var{s} in place}{(6), (7)}
\end{tableiii}
\indexiv{operations on}{mutable}{sequence}{types}
***************
*** 916,920 ****
\indexii{subscript}{assignment}
\indexii{slice}{assignment}
- \indexii{extended slice}{assignment}
\stindex{del}
\withsubitem{(list method)}{
--- 902,905 ----
***************
*** 925,957 ****
Notes:
\begin{description}
! \item[(1)] \var{t} must have the same length as the slice it is
! replacing.
!
! \item[(2)] The C implementation of Python has historically accepted
! multiple parameters and implicitly joined them into a tuple; this
! no longer works in Python 2.0. Use of this misfeature has been
! deprecated since Python 1.4.
! \item[(3)] Raises an exception when \var{x} is not a list object. The
\method{extend()} method is experimental and not supported by
mutable sequence types other than lists.
! \item[(4)] Raises \exception{ValueError} when \var{x} is not found in
\var{s}.
! \item[(5)] When a negative index is passed as the first parameter to
the \method{insert()} method, the new element is prepended to the
sequence.
! \item[(6)] The \method{pop()} method is only supported by the list and
array types. The optional argument \var{i} defaults to \code{-1},
so that by default the last item is removed and returned.
! \item[(7)] The \method{sort()} and \method{reverse()} methods modify the
list in place for economy of space when sorting or reversing a large
list. To remind you that they operate by side effect, they don't return
the sorted or reversed list.
! \item[(8)] The \method{sort()} method takes an optional argument
specifying a comparison function of two arguments (list items) which
should return a negative, zero or positive number depending on whether
--- 910,939 ----
Notes:
\begin{description}
! \item[(1)] The C implementation of Python historically accepted
! multiple parameters and implicitly joined them into a tuple;
! Use of this misfeature has been deprecated since Python 1.4,
! and became an error with the introduction of Python 2.0.
! \item[(2)] Raises an exception when \var{x} is not a list object. The
\method{extend()} method is experimental and not supported by
mutable sequence types other than lists.
! \item[(3)] Raises \exception{ValueError} when \var{x} is not found in
\var{s}.
! \item[(4)] When a negative index is passed as the first parameter to
the \method{insert()} method, the new element is prepended to the
sequence.
! \item[(5)] The \method{pop()} method is only supported by the list and
array types. The optional argument \var{i} defaults to \code{-1},
so that by default the last item is removed and returned.
! \item[(6)] The \method{sort()} and \method{reverse()} methods modify the
list in place for economy of space when sorting or reversing a large
list. To remind you that they operate by side effect, they don't return
the sorted or reversed list.
! \item[(7)] The \method{sort()} method takes an optional argument
specifying a comparison function of two arguments (list items) which
should return a negative, zero or positive number depending on whether
***************
*** 970,979 ****
\obindex{dictionary}
! A \dfn{mapping} object maps values of one type (the key type) to
arbitrary objects. Mappings are mutable objects. There is currently
only one standard mapping type, the \dfn{dictionary}. A dictionary's keys are
! almost arbitrary values. The only types of values not acceptable as
! keys are values containing lists or dictionaries or other mutable
! types that are compared by value rather than by object identity.
Numeric types used for keys obey the normal rules for numeric
comparison: if two numbers compare equal (e.g. \code{1} and
--- 952,961 ----
\obindex{dictionary}
! A \dfn{mapping} object maps immutable values to
arbitrary objects. Mappings are mutable objects. There is currently
only one standard mapping type, the \dfn{dictionary}. A dictionary's keys are
! almost arbitrary values. Only values containing lists, dictionaries
! or other mutable types (that are compared by value rather than by
! object identity) may not be used as keys.
Numeric types used for keys obey the normal rules for numeric
comparison: if two numbers compare equal (e.g. \code{1} and
***************
*** 1001,1011 ****
\ttindex{update()}
\ttindex{values()}
! \ttindex{get()}
! \ttindex{setdefault()}
! \ttindex{pop()}
! \ttindex{popitem()}
! \ttindex{iteritems()}
! \ttindex{iterkeys)}
! \ttindex{itervalues()}}
\begin{tableiii}{c|l|c}{code}{Operation}{Result}{Notes}
--- 983,987 ----
\ttindex{update()}
\ttindex{values()}
! \ttindex{get()}}
\begin{tableiii}{c|l|c}{code}{Operation}{Result}{Notes}
***************
*** 1099,1103 ****
is new in Python 2.2. The older built-in \function{open()} is an
alias for \function{file()}.}
! They are also returned
by some other built-in functions and methods, such as
\function{os.popen()} and \function{os.fdopen()} and the
--- 1075,1079 ----
is new in Python 2.2. The older built-in \function{open()} is an
alias for \function{file()}.}
! File objects are also returned
by some other built-in functions and methods, such as
\function{os.popen()} and \function{os.fdopen()} and the
***************
*** 1115,1119 ****
\begin{methoddesc}[file]{close}{}
! Close the file. A closed file cannot be read or written anymore.
Any operation which requires that the file be open will raise a
\exception{ValueError} after the file has been closed. Calling
--- 1091,1095 ----
\begin{methoddesc}[file]{close}{}
! Close the file. A closed file cannot be read or written any more.
Any operation which requires that the file be open will raise a
\exception{ValueError} after the file has been closed. Calling
***************
*** 1161,1169 ****
Read one entire line from the file. A trailing newline character is
kept in the string\footnote{
! The advantage of leaving the newline on is that an empty string
! can be returned to mean \EOF{} without being ambiguous. Another
! advantage is that (in cases where it might matter, for example. if you
want to make an exact copy of a file while scanning its lines)
! you can tell whether the last line of a file ended in a newline
or not (yes this happens!).
} (but may be absent when a file ends with an
--- 1137,1146 ----
Read one entire line from the file. A trailing newline character is
kept in the string\footnote{
! The advantage of leaving the newline on is that
! returning an empty string is then an unambiguous \EOF{}
! indication. It is also possible (in cases where it might
! matter, for example, if you
want to make an exact copy of a file while scanning its lines)
! to tell whether the last line of a file ended in a newline
or not (yes this happens!).
} (but may be absent when a file ends with an
***************
*** 1171,1175 ****
non-negative, it is a maximum byte count (including the trailing
newline) and an incomplete line may be returned.
! An empty string is returned when \EOF{} is hit
immediately. \note{Unlike \code{stdio}'s \cfunction{fgets()}, the
returned string contains null characters (\code{'\e 0'}) if they
--- 1148,1152 ----
non-negative, it is a maximum byte count (including the trailing
newline) and an incomplete line may be returned.
! An empty string is returned \emph{only} when \EOF{} is encountered
immediately. \note{Unlike \code{stdio}'s \cfunction{fgets()}, the
returned string contains null characters (\code{'\e 0'}) if they
***************
*** 1266,1281 ****
file object, of the form \samp{<\mbox{\ldots}>}. This is a read-only
attribute and may not be present on all file-like objects.
- \end{memberdesc}
-
- \begin{memberdesc}[file]{newlines}
- If Python was built with the \code{--with-universal-newlines} option
- (the default) this read-only attribute exists, and for files opened in
- universal newline read mode it keeps track of the types of newlines
- encountered while reading the file. The values it can take are
- \code{'\e r'}, \code{'\e n'}, \code{'\e r\e n'}, \code{None} (unknown,
- no newlines read yet) or a tuple containing all the newline
- types seen, to indicate that multiple
- newline conventions were encountered. For files not opened in universal
- newline read mode the value of this attribute will be \code{None}.
\end{memberdesc}
--- 1243,1246 ----