Doc/lib/libmimetypes.tex

   1 \section{\module{mimetypes} ---
   2          Map filenames to MIME types}
   3
   4 \declaremodule{standard}{mimetypes}
   5 \modulesynopsis{Mapping of filename extensions to MIME types.}
   6 \sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}
   7
   8
   9 \indexii{MIME}{content type}
  10
  11 The \module{mimetypes} module converts between a filename or URL and
  12 the MIME type associated with the filename extension.  Conversions are
  13 provided from filename to MIME type and from MIME type to filename
  14 extension; encodings are not supported for the latter conversion.
  15
  16 The module provides one class and a number of convenience functions.
  17 The functions are the normal interface to this module, but some
  18 applications may be interested in the class as well.
  19
  20 The functions described below provide the primary interface for this
  21 module.  If the module has not been initialized, they will call
  22 \function{init()} if they rely on the information \function{init()}
  23 sets up.
  24
  25
  26 \begin{funcdesc}{guess_type}{filename\optional{, strict}}
  27 Guess the type of a file based on its filename or URL, given by
  28 \var{filename}.  The return value is a tuple \code{(\var{type},
  29 \var{encoding})} where \var{type} is \code{None} if the type can't be
  30 guessed (missing or unknown suffix) or a string of the form
  31 \code{'\var{type}/\var{subtype}'}, usable for a MIME
  32 \mailheader{content-type} header\indexii{MIME}{headers}.
  33
  34 \var{encoding} is \code{None} for no encoding or the name of the
  35 program used to encode (e.g. \program{compress} or \program{gzip}).
  36 The encoding is suitable for use as a \mailheader{Content-Encoding}
  37 header, \emph{not} as a \mailheader{Content-Transfer-Encoding} header.
  38 The mappings are table driven.  Encoding suffixes are case sensitive;
  39 type suffixes are first tried case sensitively, then case
  40 insensitively.
  41
  42 Optional \var{strict} is a flag specifying whether the list of known
  43 MIME types is limited to only the official types \ulink{registered
  44 with IANA}{http://www.isi.edu/in-notes/iana/assignments/media-types}
  45 are recognized.  When \var{strict} is true (the default), only the
  46 IANA types are supported; when \var{strict} is false, some additional
  47 non-standard but commonly used MIME types are also recognized.
  48 \end{funcdesc}
  49
  50 \begin{funcdesc}{guess_all_extensions}{type\optional{, strict}}
  51 Guess the extensions for a file based on its MIME type, given by
  52 \var{type}.
  53 The return value is a list of strings giving all possible filename extensions,
  54 including the leading dot (\character{.}).  The extensions are not guaranteed
  55 to have been associated with any particular data stream, but would be mapped
  56 to the MIME type \var{type} by \function{guess_type()}.  If no extension can
  57 be guessed for \var{type}, \code{None} is returned.
  58
  59 Optional \var{strict} has the same meaning as with the
  60 \function{guess_type()} function.
  61 \end{funcdesc}
  62
  63
  64 \begin{funcdesc}{guess_extension}{type\optional{, strict}}
  65 Guess the extension for a file based on its MIME type, given by
  66 \var{type}.
  67 The return value is a string giving a filename extension, including the
  68 leading dot (\character{.}).  The extension is not guaranteed to have been
  69 associated with any particular data stream, but would be mapped to the
  70 MIME type \var{type} by \function{guess_type()}.  If no extension can
  71 be guessed for \var{type}, \code{None} is returned.
  72
  73 Optional \var{strict} has the same meaning as with the
  74 \function{guess_type()} function.
  75 \end{funcdesc}
  76
  77
  78 Some additional functions and data items are available for controlling
  79 the behavior of the module.
  80
  81
  82 \begin{funcdesc}{init}{\optional{files}}
  83 Initialize the internal data structures.  If given, \var{files} must
  84 be a sequence of file names which should be used to augment the
  85 default type map.  If omitted, the file names to use are taken from
  86 \constant{knownfiles}.  Each file named in \var{files} or
  87 \constant{knownfiles} takes precedence over those named before it.
  88 Calling \function{init()} repeatedly is allowed.
  89 \end{funcdesc}
  90
  91 \begin{funcdesc}{read_mime_types}{filename}
  92 Load the type map given in the file \var{filename}, if it exists.  The
  93 type map is returned as a dictionary mapping filename extensions,
  94 including the leading dot (\character{.}), to strings of the form
  95 \code{'\var{type}/\var{subtype}'}.  If the file \var{filename} does
  96 not exist or cannot be read, \code{None} is returned.
  97 \end{funcdesc}
  98
  99
 100 \begin{funcdesc}{add_type}{type, ext\optional{, strict}}
 101 Add a mapping from the mimetype \var{type} to the extension \var{ext}.
 102 When the extension is already known, the new type will replace the old
 103 one. When the type is already known the extension will be added
 104 to the list of known extensions.
 105
 106 When \var{strict} is the mapping will added to the official
 107 MIME types, otherwise to the non-standard ones.
 108 \end{funcdesc}
 109
 110
 111 \begin{datadesc}{inited}
 112 Flag indicating whether or not the global data structures have been
 113 initialized.  This is set to true by \function{init()}.
 114 \end{datadesc}
 115
 116 \begin{datadesc}{knownfiles}
 117 List of type map file names commonly installed.  These files are
 118 typically named \file{mime.types} and are installed in different
 119 locations by different packages.\index{file!mime.types}
 120 \end{datadesc}
 121
 122 \begin{datadesc}{suffix_map}
 123 Dictionary mapping suffixes to suffixes.  This is used to allow
 124 recognition of encoded files for which the encoding and the type are
 125 indicated by the same extension.  For example, the \file{.tgz}
 126 extension is mapped to \file{.tar.gz} to allow the encoding and type
 127 to be recognized separately.
 128 \end{datadesc}
 129
 130 \begin{datadesc}{encodings_map}
 131 Dictionary mapping filename extensions to encoding types.
 132 \end{datadesc}
 133
 134 \begin{datadesc}{types_map}
 135 Dictionary mapping filename extensions to MIME types.
 136 \end{datadesc}
 137
 138 \begin{datadesc}{common_types}
 139 Dictionary mapping filename extensions to non-standard, but commonly
 140 found MIME types.
 141 \end{datadesc}
 142
 143
 144 The \class{MimeTypes} class may be useful for applications which may
 145 want more than one MIME-type database:
 146
 147 \begin{classdesc}{MimeTypes}{\optional{filenames}}
 148   This class represents a MIME-types database.  By default, it
 149   provides access to the same database as the rest of this module.
 150   The initial database is a copy of that provided by the module, and
 151   may be extended by loading additional \file{mime.types}-style files
 152   into the database using the \method{read()} or \method{readfp()}
 153   methods.  The mapping dictionaries may also be cleared before
 154   loading additional data if the default data is not desired.
 155
 156   The optional \var{filenames} parameter can be used to cause
 157   additional files to be loaded ``on top'' of the default database.
 158
 159   \versionadded{2.2}
 160 \end{classdesc}
 161
 162
 163 \subsection{MimeTypes Objects \label{mimetypes-objects}}
 164
 165 \class{MimeTypes} instances provide an interface which is very like
 166 that of the \refmodule{mimetypes} module.
 167
 168 \begin{datadesc}{suffix_map}
 169   Dictionary mapping suffixes to suffixes.  This is used to allow
 170   recognition of encoded files for which the encoding and the type are
 171   indicated by the same extension.  For example, the \file{.tgz}
 172   extension is mapped to \file{.tar.gz} to allow the encoding and type
 173   to be recognized separately.  This is initially a copy of the global
 174   \code{suffix_map} defined in the module.
 175 \end{datadesc}
 176
 177 \begin{datadesc}{encodings_map}
 178   Dictionary mapping filename extensions to encoding types.  This is
 179   initially a copy of the global \code{encodings_map} defined in the
 180   module.
 181 \end{datadesc}
 182
 183 \begin{datadesc}{types_map}
 184   Dictionary mapping filename extensions to MIME types.  This is
 185   initially a copy of the global \code{types_map} defined in the
 186   module.
 187 \end{datadesc}
 188
 189 \begin{datadesc}{common_types}
 190   Dictionary mapping filename extensions to non-standard, but commonly
 191   found MIME types.  This is initially a copy of the global
 192   \code{common_types} defined in the module.
 193 \end{datadesc}
 194
 195 \begin{methoddesc}{guess_extension}{type\optional{, strict}}
 196   Similar to the \function{guess_extension()} function, using the
 197   tables stored as part of the object.
 198 \end{methoddesc}
 199
 200 \begin{methoddesc}{guess_type}{url\optional{, strict}}
 201   Similar to the \function{guess_type()} function, using the tables
 202   stored as part of the object.
 203 \end{methoddesc}
 204
 205 \begin{methoddesc}{read}{path}
 206   Load MIME information from a file named \var{path}.  This uses
 207   \method{readfp()} to parse the file.
 208 \end{methoddesc}
 209
 210 \begin{methoddesc}{readfp}{file}
 211   Load MIME type information from an open file.  The file must have
 212   the format of the standard \file{mime.types} files.
 213 \end{methoddesc}