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author | cinap_lenrek <cinap_lenrek@localhost> | 2011-05-03 11:25:13 +0000 |
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committer | cinap_lenrek <cinap_lenrek@localhost> | 2011-05-03 11:25:13 +0000 |
commit | 458120dd40db6b4df55a4e96b650e16798ef06a0 (patch) | |
tree | 8f82685be24fef97e715c6f5ca4c68d34d5074ee /sys/src/cmd/python/Doc/lib/libarray.tex | |
parent | 3a742c699f6806c1145aea5149bf15de15a0afd7 (diff) |
add hg and python
Diffstat (limited to 'sys/src/cmd/python/Doc/lib/libarray.tex')
-rw-r--r-- | sys/src/cmd/python/Doc/lib/libarray.tex | 241 |
1 files changed, 241 insertions, 0 deletions
diff --git a/sys/src/cmd/python/Doc/lib/libarray.tex b/sys/src/cmd/python/Doc/lib/libarray.tex new file mode 100644 index 000000000..eaf58884e --- /dev/null +++ b/sys/src/cmd/python/Doc/lib/libarray.tex @@ -0,0 +1,241 @@ +\section{\module{array} --- + Efficient arrays of numeric values} + +\declaremodule{builtin}{array} +\modulesynopsis{Efficient arrays of uniformly typed numeric values.} + + +This module defines an object type which can efficiently represent +an array of basic values: characters, integers, floating point +numbers. Arrays\index{arrays} are sequence types and behave very much +like lists, except that the type of objects stored in them is +constrained. The type is specified at object creation time by using a +\dfn{type code}, which is a single character. The following type +codes are defined: + +\begin{tableiv}{c|l|l|c}{code}{Type code}{C Type}{Python Type}{Minimum size in bytes} + \lineiv{'c'}{char} {character} {1} + \lineiv{'b'}{signed char} {int} {1} + \lineiv{'B'}{unsigned char} {int} {1} + \lineiv{'u'}{Py_UNICODE} {Unicode character}{2} + \lineiv{'h'}{signed short} {int} {2} + \lineiv{'H'}{unsigned short}{int} {2} + \lineiv{'i'}{signed int} {int} {2} + \lineiv{'I'}{unsigned int} {long} {2} + \lineiv{'l'}{signed long} {int} {4} + \lineiv{'L'}{unsigned long} {long} {4} + \lineiv{'f'}{float} {float} {4} + \lineiv{'d'}{double} {float} {8} +\end{tableiv} + +The actual representation of values is determined by the machine +architecture (strictly speaking, by the C implementation). The actual +size can be accessed through the \member{itemsize} attribute. The values +stored for \code{'L'} and \code{'I'} items will be represented as +Python long integers when retrieved, because Python's plain integer +type cannot represent the full range of C's unsigned (long) integers. + + +The module defines the following type: + +\begin{funcdesc}{array}{typecode\optional{, initializer}} +Return a new array whose items are restricted by \var{typecode}, +and initialized from the optional \var{initializer} value, which +must be a list, string, or iterable over elements of the +appropriate type. +\versionchanged[Formerly, only lists or strings were accepted]{2.4} +If given a list or string, the initializer is passed to the +new array's \method{fromlist()}, \method{fromstring()}, or +\method{fromunicode()} method (see below) to add initial items to +the array. Otherwise, the iterable initializer is passed to the +\method{extend()} method. +\end{funcdesc} + +\begin{datadesc}{ArrayType} +Obsolete alias for \function{array}. +\end{datadesc} + + +Array objects support the ordinary sequence operations of +indexing, slicing, concatenation, and multiplication. When using +slice assignment, the assigned value must be an array object with the +same type code; in all other cases, \exception{TypeError} is raised. +Array objects also implement the buffer interface, and may be used +wherever buffer objects are supported. + +The following data items and methods are also supported: + +\begin{memberdesc}[array]{typecode} +The typecode character used to create the array. +\end{memberdesc} + +\begin{memberdesc}[array]{itemsize} +The length in bytes of one array item in the internal representation. +\end{memberdesc} + + +\begin{methoddesc}[array]{append}{x} +Append a new item with value \var{x} to the end of the array. +\end{methoddesc} + +\begin{methoddesc}[array]{buffer_info}{} +Return a tuple \code{(\var{address}, \var{length})} giving the current +memory address and the length in elements of the buffer used to hold +array's contents. The size of the memory buffer in bytes can be +computed as \code{\var{array}.buffer_info()[1] * +\var{array}.itemsize}. This is occasionally useful when working with +low-level (and inherently unsafe) I/O interfaces that require memory +addresses, such as certain \cfunction{ioctl()} operations. The +returned numbers are valid as long as the array exists and no +length-changing operations are applied to it. + +\note{When using array objects from code written in C or +\Cpp{} (the only way to effectively make use of this information), it +makes more sense to use the buffer interface supported by array +objects. This method is maintained for backward compatibility and +should be avoided in new code. The buffer interface is documented in +the \citetitle[../api/newTypes.html]{Python/C API Reference Manual}.} +\end{methoddesc} + +\begin{methoddesc}[array]{byteswap}{} +``Byteswap'' all items of the array. This is only supported for +values which are 1, 2, 4, or 8 bytes in size; for other types of +values, \exception{RuntimeError} is raised. It is useful when reading +data from a file written on a machine with a different byte order. +\end{methoddesc} + +\begin{methoddesc}[array]{count}{x} +Return the number of occurrences of \var{x} in the array. +\end{methoddesc} + +\begin{methoddesc}[array]{extend}{iterable} +Append items from \var{iterable} to the end of the array. If +\var{iterable} is another array, it must have \emph{exactly} the same +type code; if not, \exception{TypeError} will be raised. If +\var{iterable} is not an array, it must be iterable and its +elements must be the right type to be appended to the array. +\versionchanged[Formerly, the argument could only be another array]{2.4} +\end{methoddesc} + +\begin{methoddesc}[array]{fromfile}{f, n} +Read \var{n} items (as machine values) from the file object \var{f} +and append them to the end of the array. If less than \var{n} items +are available, \exception{EOFError} is raised, but the items that were +available are still inserted into the array. \var{f} must be a real +built-in file object; something else with a \method{read()} method won't +do. +\end{methoddesc} + +\begin{methoddesc}[array]{fromlist}{list} +Append items from the list. This is equivalent to +\samp{for x in \var{list}:\ a.append(x)} +except that if there is a type error, the array is unchanged. +\end{methoddesc} + +\begin{methoddesc}[array]{fromstring}{s} +Appends items from the string, interpreting the string as an +array of machine values (as if it had been read from a +file using the \method{fromfile()} method). +\end{methoddesc} + +\begin{methoddesc}[array]{fromunicode}{s} +Extends this array with data from the given unicode string. The array +must be a type \code{'u'} array; otherwise a \exception{ValueError} +is raised. Use \samp{array.fromstring(ustr.decode(enc))} to +append Unicode data to an array of some other type. +\end{methoddesc} + +\begin{methoddesc}[array]{index}{x} +Return the smallest \var{i} such that \var{i} is the index of +the first occurrence of \var{x} in the array. +\end{methoddesc} + +\begin{methoddesc}[array]{insert}{i, x} +Insert a new item with value \var{x} in the array before position +\var{i}. Negative values are treated as being relative to the end +of the array. +\end{methoddesc} + +\begin{methoddesc}[array]{pop}{\optional{i}} +Removes the item with the index \var{i} from the array and returns +it. The optional argument defaults to \code{-1}, so that by default +the last item is removed and returned. +\end{methoddesc} + +\begin{methoddesc}[array]{read}{f, n} +\deprecated {1.5.1} + {Use the \method{fromfile()} method.} +Read \var{n} items (as machine values) from the file object \var{f} +and append them to the end of the array. If less than \var{n} items +are available, \exception{EOFError} is raised, but the items that were +available are still inserted into the array. \var{f} must be a real +built-in file object; something else with a \method{read()} method won't +do. +\end{methoddesc} + +\begin{methoddesc}[array]{remove}{x} +Remove the first occurrence of \var{x} from the array. +\end{methoddesc} + +\begin{methoddesc}[array]{reverse}{} +Reverse the order of the items in the array. +\end{methoddesc} + +\begin{methoddesc}[array]{tofile}{f} +Write all items (as machine values) to the file object \var{f}. +\end{methoddesc} + +\begin{methoddesc}[array]{tolist}{} +Convert the array to an ordinary list with the same items. +\end{methoddesc} + +\begin{methoddesc}[array]{tostring}{} +Convert the array to an array of machine values and return the +string representation (the same sequence of bytes that would +be written to a file by the \method{tofile()} method.) +\end{methoddesc} + +\begin{methoddesc}[array]{tounicode}{} +Convert the array to a unicode string. The array must be +a type \code{'u'} array; otherwise a \exception{ValueError} is raised. +Use \samp{array.tostring().decode(enc)} to obtain a unicode string +from an array of some other type. +\end{methoddesc} + +\begin{methoddesc}[array]{write}{f} +\deprecated {1.5.1} + {Use the \method{tofile()} method.} +Write all items (as machine values) to the file object \var{f}. +\end{methoddesc} + +When an array object is printed or converted to a string, it is +represented as \code{array(\var{typecode}, \var{initializer})}. The +\var{initializer} is omitted if the array is empty, otherwise it is a +string if the \var{typecode} is \code{'c'}, otherwise it is a list of +numbers. The string is guaranteed to be able to be converted back to +an array with the same type and value using reverse quotes +(\code{``}), so long as the \function{array()} function has been +imported using \code{from array import array}. Examples: + +\begin{verbatim} +array('l') +array('c', 'hello world') +array('u', u'hello \textbackslash u2641') +array('l', [1, 2, 3, 4, 5]) +array('d', [1.0, 2.0, 3.14]) +\end{verbatim} + + +\begin{seealso} + \seemodule{struct}{Packing and unpacking of heterogeneous binary data.} + \seemodule{xdrlib}{Packing and unpacking of External Data + Representation (XDR) data as used in some remote + procedure call systems.} + \seetitle[http://numpy.sourceforge.net/numdoc/HTML/numdoc.htm]{The + Numerical Python Manual}{The Numeric Python extension + (NumPy) defines another array type; see + \url{http://numpy.sourceforge.net/} for further information + about Numerical Python. (A PDF version of the NumPy manual + is available at + \url{http://numpy.sourceforge.net/numdoc/numdoc.pdf}).} +\end{seealso} |