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created 2020-01-14 07:04 UTC

elodie.external.pyexiftool.ExifTool.enter() A

↳ Parent: elodie.external.pyexiftool

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# -*- coding: utf-8 -*-
# PyExifTool <http://github.com/smarnach/pyexiftool>
# Copyright 2012 Sven Marnach. Enhancements by Leo Broska

# This file is part of PyExifTool.
#
# PyExifTool is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# PyExifTool is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with PyExifTool.  If not, see <http://www.gnu.org/licenses/>.

"""
PyExifTool is a Python library to communicate with an instance of Phil
Harvey's excellent ExifTool_ command-line application.  The library
provides the class :py:class:`ExifTool` that runs the command-line
tool in batch mode and features methods to send commands to that
program, including methods to extract meta-information from one or
more image files.  Since ``exiftool`` is run in batch mode, only a
single instance needs to be launched and can be reused for many
queries.  This is much more efficient than launching a separate
process for every single query.

.. _ExifTool: http://www.sno.phy.queensu.ca/~phil/exiftool/

The source code can be checked out from the github repository with

::

    git clone git://github.com/smarnach/pyexiftool.git

Alternatively, you can download a tarball_.  There haven't been any
releases yet.

.. _tarball: https://github.com/smarnach/pyexiftool/tarball/master

PyExifTool is licenced under GNU GPL version 3 or later.

Example usage::

    import exiftool

    files = ["a.jpg", "b.png", "c.tif"]
    with exiftool.ExifTool() as et:
        metadata = et.get_metadata_batch(files)
    for d in metadata:
        print("{:20.20} {:20.20}".format(d["SourceFile"],
                                         d["EXIF:DateTimeOriginal"]))
"""

from __future__ import unicode_literals

import sys
import subprocess
import os
import json
import warnings
import logging
import codecs

from future.utils import with_metaclass

try:        # Py3k compatibility
    basestring

except NameError:
    basestring = (bytes, str)

executable = "exiftool"
"""The name of the executable to run.

If the executable is not located in one of the paths listed in the
``PATH`` environment variable, the full path should be given here.
"""

# Sentinel indicating the end of the output of a sequence of commands.
# The standard value should be fine.
sentinel = b"{ready}"

# The block size when reading from exiftool.  The standard value
# should be fine, though other values might give better performance in
# some cases.
block_size = 4096

# constants related to keywords manipulations 
KW_TAGNAME = "IPTC:Keywords"
KW_REPLACE, KW_ADD, KW_REMOVE = range(3)


# This code has been adapted from Lib/os.py in the Python source tree
# (sha1 265e36e277f3)
def _fscodec():
    encoding = sys.getfilesystemencoding()
    errors = "strict"
    if encoding != "mbcs":
        try:
            codecs.lookup_error("surrogateescape")
        except LookupError:
            pass
        else:
            errors = "surrogateescape"

    def fsencode(filename):
        """
        Encode filename to the filesystem encoding with 'surrogateescape' error
        handler, return bytes unchanged. On Windows, use 'strict' error handler if
        the file system encoding is 'mbcs' (which is the default encoding).
        """
        if isinstance(filename, bytes):
            return filename
        else:
            return filename.encode(encoding, errors)

    return fsencode

fsencode = _fscodec()
del _fscodec

#string helper
def strip_nl (s):
    return ' '.join(s.splitlines())


# Error checking function
# Note: They are quite fragile, beacsue teh just parse the output text from exiftool
def check_ok (result):
    """Evaluates the output from a exiftool write operation (e.g. `set_tags`)
    
    The argument is the result from the execute method.
    
    The result is True or False.
    """
    return not result is None and (not "due to errors" in result)

def format_error (result):
    """Evaluates the output from a exiftool write operation (e.g. `set_tags`)
    
    The argument is the result from the execute method.
    
    The result is a human readable one-line string.
    """
    if check_ok (result):
        return 'exiftool finished probably properly. ("%s")' % strip_nl(result)
    else:        
        if result is None:
            return "exiftool operation can't be evaluated: No result given"
        else:
            return 'exiftool finished with error: "%s"' % strip_nl(result) 

class Singleton(type):
    """Metaclass to use the singleton [anti-]pattern"""
    instance = None

    def __call__(cls, *args, **kwargs):
        if cls.instance is None:
            cls.instance = super(Singleton, cls).__call__(*args, **kwargs)
        return cls.instance

class ExifTool(object, with_metaclass(Singleton)):
    """Run the `exiftool` command-line tool and communicate to it.

    You can pass two arguments to the constructor:
    - ``addedargs`` (list of strings): contains additional paramaters for
      the stay-open instance of exiftool
    - ``executable`` (string): file name of the ``exiftool`` executable.
      The default value ``exiftool`` will only work if the executable
      is in your ``PATH``

    Most methods of this class are only available after calling
    :py:meth:`start()`, which will actually launch the subprocess.  To
    avoid leaving the subprocess running, make sure to call
    :py:meth:`terminate()` method when finished using the instance.
    This method will also be implicitly called when the instance is
    garbage collected, but there are circumstance when this won't ever
    happen, so you should not rely on the implicit process
    termination.  Subprocesses won't be automatically terminated if
    the parent process exits, so a leaked subprocess will stay around
    until manually killed.

    A convenient way to make sure that the subprocess is terminated is
    to use the :py:class:`ExifTool` instance as a context manager::

        with ExifTool() as et:
            ...

    .. warning:: Note that there is no error handling.  Nonsensical
       options will be silently ignored by exiftool, so there's not
       much that can be done in that regard.  You should avoid passing
       non-existent files to any of the methods, since this will lead
       to undefied behaviour.

    .. py:attribute:: running

       A Boolean value indicating whether this instance is currently
       associated with a running subprocess.
    """

    def __init__(self, executable_=None, addedargs=None):
        
        if executable_ is None:
            self.executable = executable
        else:
            self.executable = executable_

        if addedargs is None:
            self.addedargs = []
        elif type(addedargs) is list:
            self.addedargs = addedargs
        else:
            raise TypeError("addedargs not a list of strings")
        
        self.running = False

    def start(self):
        """Start an ``exiftool`` process in batch mode for this instance.

        This method will issue a ``UserWarning`` if the subprocess is
        already running.  The process is started with the ``-G`` and
        ``-n`` as common arguments, which are automatically included
        in every command you run with :py:meth:`execute()`.
        """
        if self.running:
            warnings.warn("ExifTool already running; doing nothing.")
            return
        with open(os.devnull, "w") as devnull:
            procargs = [self.executable, "-stay_open", "True",  "-@", "-",
                 "-common_args", "-G", "-n"];
            procargs.extend(self.addedargs)
            logging.debug(procargs) 
            self._process = subprocess.Popen(
                procargs,
                stdin=subprocess.PIPE, stdout=subprocess.PIPE,
                stderr=devnull)
        self.running = True

    def terminate(self):
        """Terminate the ``exiftool`` process of this instance.

        If the subprocess isn't running, this method will do nothing.
        """
        if not self.running:
            return
        self._process.stdin.write(b"-stay_open\nFalse\n")
        self._process.stdin.flush()
        self._process.communicate()
        del self._process
        self.running = False

    def __enter__(self):
        self.start()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.terminate()

    def __del__(self):
        self.terminate()

    def execute(self, *params):
        """Execute the given batch of parameters with ``exiftool``.

        This method accepts any number of parameters and sends them to
        the attached ``exiftool`` process.  The process must be
        running, otherwise ``ValueError`` is raised.  The final
        ``-execute`` necessary to actually run the batch is appended
        automatically; see the documentation of :py:meth:`start()` for
        the common options.  The ``exiftool`` output is read up to the
        end-of-output sentinel and returned as a raw ``bytes`` object,
        excluding the sentinel.

        The parameters must also be raw ``bytes``, in whatever
        encoding exiftool accepts.  For filenames, this should be the
        system's filesystem encoding.

        .. note:: This is considered a low-level method, and should
           rarely be needed by application developers.
        """
        if not self.running:
            raise ValueError("ExifTool instance not running.")
        self._process.stdin.write(b"\n".join(params + (b"-execute\n",)))
        self._process.stdin.flush()
        output = b""
        fd = self._process.stdout.fileno()
        while not output[-32:].strip().endswith(sentinel):
            output += os.read(fd, block_size)
        return output.strip()[:-len(sentinel)]

    def execute_json(self, *params):
        """Execute the given batch of parameters and parse the JSON output.

        This method is similar to :py:meth:`execute()`.  It
        automatically adds the parameter ``-j`` to request JSON output
        from ``exiftool`` and parses the output.  The return value is
        a list of dictionaries, mapping tag names to the corresponding
        values.  All keys are Unicode strings with the tag names
        including the ExifTool group name in the format <group>:<tag>.
        The values can have multiple types.  All strings occurring as
        values will be Unicode strings.  Each dictionary contains the
        name of the file it corresponds to in the key ``"SourceFile"``.

        The parameters to this function must be either raw strings
        (type ``str`` in Python 2.x, type ``bytes`` in Python 3.x) or
        Unicode strings (type ``unicode`` in Python 2.x, type ``str``
        in Python 3.x).  Unicode strings will be encoded using
        system's filesystem encoding.  This behaviour means you can
        pass in filenames according to the convention of the
        respective Python version – as raw strings in Python 2.x and
        as Unicode strings in Python 3.x.
        """
        params = map(fsencode, params)
        # Some latin bytes won't decode to utf-8.
        # Try utf-8 and fallback to latin.
        # http://stackoverflow.com/a/5552623/1318758
        # https://github.com/jmathai/elodie/issues/127
        try:
            return json.loads(self.execute(b"-j", *params).decode("utf-8"))
        except UnicodeDecodeError as e:
            return json.loads(self.execute(b"-j", *params).decode("latin-1"))

    def get_metadata_batch(self, filenames):
        """Return all meta-data for the given files.

        The return value will have the format described in the
        documentation of :py:meth:`execute_json()`.
        """
        return self.execute_json(*filenames)

    def get_metadata(self, filename):
        """Return meta-data for a single file.

        The returned dictionary has the format described in the
        documentation of :py:meth:`execute_json()`.
        """
        return self.execute_json(filename)[0]

    def get_tags_batch(self, tags, filenames):
        """Return only specified tags for the given files.

        The first argument is an iterable of tags.  The tag names may
        include group names, as usual in the format <group>:<tag>.

        The second argument is an iterable of file names.

        The format of the return value is the same as for
        :py:meth:`execute_json()`.
        """
        # Explicitly ruling out strings here because passing in a
        # string would lead to strange and hard-to-find errors
        if isinstance(tags, basestring):
            raise TypeError("The argument 'tags' must be "
                            "an iterable of strings")
        if isinstance(filenames, basestring):
            raise TypeError("The argument 'filenames' must be "
                            "an iterable of strings")
        params = ["-" + t for t in tags]
        params.extend(filenames)
        return self.execute_json(*params)

    def get_tags(self, tags, filename):
        """Return only specified tags for a single file.

        The returned dictionary has the format described in the
        documentation of :py:meth:`execute_json()`.
        """
        return self.get_tags_batch(tags, [filename])[0]

    def get_tag_batch(self, tag, filenames):
        """Extract a single tag from the given files.

        The first argument is a single tag name, as usual in the
        format <group>:<tag>.

        The second argument is an iterable of file names.

        The return value is a list of tag values or ``None`` for
        non-existent tags, in the same order as ``filenames``.
        """
        data = self.get_tags_batch([tag], filenames)
        result = []
        for d in data:
            d.pop("SourceFile")
            result.append(next(iter(d.values()), None))
        return result

    def get_tag(self, tag, filename):
        """Extract a single tag from a single file.

        The return value is the value of the specified tag, or
        ``None`` if this tag was not found in the file.
        """
        return self.get_tag_batch(tag, [filename])[0]

    def set_tags_batch(self, tags, filenames):
        """Writes the values of the specified tags for the given files.

        The first argument is a dictionary of tags and values.  The tag names may
        include group names, as usual in the format <group>:<tag>.

        The second argument is an iterable of file names.

        The format of the return value is the same as for
        :py:meth:`execute()`.
        
        It can be passed into `check_ok()` and `format_error()`.
        """
        # Explicitly ruling out strings here because passing in a
        # string would lead to strange and hard-to-find errors
        if isinstance(tags, basestring):
            raise TypeError("The argument 'tags' must be dictionary "
                            "of strings")
        if isinstance(filenames, basestring):
            raise TypeError("The argument 'filenames' must be "
                            "an iterable of strings")
                
        params = []
        params_utf8 = []
        for tag, value in tags.items():
            params.append(u'-%s=%s' % (tag, value))
            
        params.extend(filenames)
        params_utf8 = [x.encode('utf-8') for x in params]
        return self.execute(*params_utf8)

    def set_tags(self, tags, filename):
        """Writes the values of the specified tags for the given file.

        This is a convenience function derived from `set_tags_batch()`.
        Only difference is that it takes as last arugemnt only one file name
        as a string. 
        """
        return self.set_tags_batch(tags, [filename])
    
    def set_keywords_batch(self, mode, keywords, filenames):
        """Modifies the keywords tag for the given files.

        The first argument is the operation mode:
        KW_REPLACE: Replace (i.e. set) the full keywords tag with `keywords`.
        KW_ADD:     Add `keywords` to the keywords tag. 
                    If a keyword is present, just keep it.
        KW_REMOVE:  Remove `keywords` from the keywords tag. 
                    If a keyword wasn't present, just leave it.

        The second argument is an iterable of key words.    

        The third argument is an iterable of file names.

        The format of the return value is the same as for
        :py:meth:`execute()`.
        
        It can be passed into `check_ok()` and `format_error()`.
        """
        # Explicitly ruling out strings here because passing in a
        # string would lead to strange and hard-to-find errors
        if isinstance(keywords, basestring):
            raise TypeError("The argument 'keywords' must be "
                            "an iterable of strings")
        if isinstance(filenames, basestring):
            raise TypeError("The argument 'filenames' must be "
                            "an iterable of strings")
                
        params = []    
            
        kw_operation = {KW_REPLACE:"-%s=%s",
                        KW_ADD:"-%s+=%s",
                        KW_REMOVE:"-%s-=%s"}[mode]

        kw_params = [ kw_operation % (KW_TAGNAME, w)  for w in keywords ]
        
        params.extend(kw_params)            
        params.extend(filenames)
        logging.debug (params)
        return self.execute(*params)
    
    def set_keywords(self, mode, keywords, filename):
        """Modifies the keywords tag for the given file.

        This is a convenience function derived from `set_keywords_batch()`.
        Only difference is that it takes as last argument only one file name
        as a string. 
        """
        return self.set_keywords_batch(mode, keywords, [filename])


1			# -- coding: utf-8 --
2			# PyExifTool <http://github.com/smarnach/pyexiftool>
3			# Copyright 2012 Sven Marnach. Enhancements by Leo Broska
4
5			# This file is part of PyExifTool.
6			#
7			# PyExifTool is free software: you can redistribute it and/or modify
8			# it under the terms of the GNU General Public License as published by
9			# the Free Software Foundation, either version 3 of the License, or
10			# (at your option) any later version.
11			#
12			# PyExifTool is distributed in the hope that it will be useful,
13			# but WITHOUT ANY WARRANTY; without even the implied warranty of
14			# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15			# GNU General Public License for more details.
16			#
17			# You should have received a copy of the GNU General Public License
18			# along with PyExifTool. If not, see <http://www.gnu.org/licenses/>.
19
20			"""
21			PyExifTool is a Python library to communicate with an instance of Phil
22			Harvey's excellent ExifTool_ command-line application. The library
23			provides the class :py:class:`ExifTool` that runs the command-line
24			tool in batch mode and features methods to send commands to that
25			program, including methods to extract meta-information from one or
26			more image files. Since ``exiftool`` is run in batch mode, only a
27			single instance needs to be launched and can be reused for many
28			queries. This is much more efficient than launching a separate
29			process for every single query.
30
31			.. _ExifTool: http://www.sno.phy.queensu.ca/~phil/exiftool/
32
33			The source code can be checked out from the github repository with
34
35			::
36
37			git clone git://github.com/smarnach/pyexiftool.git
38
39			Alternatively, you can download a tarball_. There haven't been any
40			releases yet.
41
42			.. _tarball: https://github.com/smarnach/pyexiftool/tarball/master
43
44			PyExifTool is licenced under GNU GPL version 3 or later.
45
46			Example usage::
47
48			import exiftool
49
50			files = ["a.jpg", "b.png", "c.tif"]
51			with exiftool.ExifTool() as et:
52			metadata = et.get_metadata_batch(files)
53			for d in metadata:
54			print("{:20.20} {:20.20}".format(d["SourceFile"],
55			d["EXIF:DateTimeOriginal"]))
56			"""
57
58			from __future__ import unicode_literals
59
60			import sys
61			import subprocess
62			import os
63			import json
64			import warnings
65			import logging
66			import codecs
67
68			from future.utils import with_metaclass
69
70			try: # Py3k compatibility
71			basestring
			0 ignored issues – show Comprehensibility Best Practice introduced 2019-01-24 14:20 UTC by Report Bug Copy Issue Report The variable `basestring` does not seem to be defined. Loading history...
72			except NameError:
73			basestring = (bytes, str)
74
75			executable = "exiftool"
76			"""The name of the executable to run.
77
78			If the executable is not located in one of the paths listed in the
79			``PATH`` environment variable, the full path should be given here.
80			"""
81
82			# Sentinel indicating the end of the output of a sequence of commands.
83			# The standard value should be fine.
84			sentinel = b"{ready}"
85
86			# The block size when reading from exiftool. The standard value
87			# should be fine, though other values might give better performance in
88			# some cases.
89			block_size = 4096
90
91			# constants related to keywords manipulations
92			KW_TAGNAME = "IPTC:Keywords"
93			KW_REPLACE, KW_ADD, KW_REMOVE = range(3)
94
95
96			# This code has been adapted from Lib/os.py in the Python source tree
97			# (sha1 265e36e277f3)
98			def _fscodec():
99			encoding = sys.getfilesystemencoding()
100			errors = "strict"
101			if encoding != "mbcs":
102			try:
103			codecs.lookup_error("surrogateescape")
104			except LookupError:
105			pass
106			else:
107			errors = "surrogateescape"
108
109			def fsencode(filename):
110			"""
111			Encode filename to the filesystem encoding with 'surrogateescape' error
112			handler, return bytes unchanged. On Windows, use 'strict' error handler if
113			the file system encoding is 'mbcs' (which is the default encoding).
114			"""
115			if isinstance(filename, bytes):
116			return filename
117			else:
118			return filename.encode(encoding, errors)
119
120			return fsencode
121
122			fsencode = _fscodec()
123			del _fscodec
124
125			#string helper
126			def strip_nl (s):
127			return ' '.join(s.splitlines())
128
129
130			# Error checking function
131			# Note: They are quite fragile, beacsue teh just parse the output text from exiftool
132			def check_ok (result):
133			"""Evaluates the output from a exiftool write operation (e.g. `set_tags`)
134
135			The argument is the result from the execute method.
136
137			The result is True or False.
138			"""
139			return not result is None and (not "due to errors" in result)
140
141			def format_error (result):
142			"""Evaluates the output from a exiftool write operation (e.g. `set_tags`)
143
144			The argument is the result from the execute method.
145
146			The result is a human readable one-line string.
147			"""
148			if check_ok (result):
149			return 'exiftool finished probably properly. ("%s")' % strip_nl(result)
150			else:
151			if result is None:
152			return "exiftool operation can't be evaluated: No result given"
153			else:
154			return 'exiftool finished with error: "%s"' % strip_nl(result)
155
156			class Singleton(type):
157			"""Metaclass to use the singleton [anti-]pattern"""
158			instance = None
159
160			def __call__(cls, args, *kwargs):
161			if cls.instance is None:
162			cls.instance = super(Singleton, cls).__call__(args, *kwargs)
163			return cls.instance
164
165			class ExifTool(object, with_metaclass(Singleton)):
166			"""Run the `exiftool` command-line tool and communicate to it.
167
168			You can pass two arguments to the constructor:
169			- ``addedargs`` (list of strings): contains additional paramaters for
170			the stay-open instance of exiftool
171			- ``executable`` (string): file name of the ``exiftool`` executable.
172			The default value ``exiftool`` will only work if the executable
173			is in your ``PATH``
174
175			Most methods of this class are only available after calling
176			:py:meth:`start()`, which will actually launch the subprocess. To
177			avoid leaving the subprocess running, make sure to call
178			:py:meth:`terminate()` method when finished using the instance.
179			This method will also be implicitly called when the instance is
180			garbage collected, but there are circumstance when this won't ever
181			happen, so you should not rely on the implicit process
182			termination. Subprocesses won't be automatically terminated if
183			the parent process exits, so a leaked subprocess will stay around
184			until manually killed.
185
186			A convenient way to make sure that the subprocess is terminated is
187			to use the :py:class:`ExifTool` instance as a context manager::
188
189			with ExifTool() as et:
190			...
191
192			.. warning:: Note that there is no error handling. Nonsensical
193			options will be silently ignored by exiftool, so there's not
194			much that can be done in that regard. You should avoid passing
195			non-existent files to any of the methods, since this will lead
196			to undefied behaviour.
197
198			.. py:attribute:: running
199
200			A Boolean value indicating whether this instance is currently
201			associated with a running subprocess.
202			"""
203
204			def __init__(self, executable_=None, addedargs=None):
205
206			if executable_ is None:
207			self.executable = executable
208			else:
209			self.executable = executable_
210
211			if addedargs is None:
212			self.addedargs = []
213			elif type(addedargs) is list:
214			self.addedargs = addedargs
215			else:
216			raise TypeError("addedargs not a list of strings")
217
218			self.running = False
219
220			def start(self):
221			"""Start an ``exiftool`` process in batch mode for this instance.
222
223			This method will issue a ``UserWarning`` if the subprocess is
224			already running. The process is started with the ``-G`` and
225			``-n`` as common arguments, which are automatically included
226			in every command you run with :py:meth:`execute()`.
227			"""
228			if self.running:
229			warnings.warn("ExifTool already running; doing nothing.")
230			return
231			with open(os.devnull, "w") as devnull:
232			procargs = [self.executable, "-stay_open", "True", "-@", "-",
233			"-common_args", "-G", "-n"];
234			procargs.extend(self.addedargs)
235			logging.debug(procargs)
236			self._process = subprocess.Popen(
237			procargs,
238			stdin=subprocess.PIPE, stdout=subprocess.PIPE,
239			stderr=devnull)
240			self.running = True
241
242			def terminate(self):
243			"""Terminate the ``exiftool`` process of this instance.
244
245			If the subprocess isn't running, this method will do nothing.
246			"""
247			if not self.running:
248			return
249			self._process.stdin.write(b"-stay_open\nFalse\n")
250			self._process.stdin.flush()
251			self._process.communicate()
252			del self._process
253			self.running = False
254
255			def __enter__(self):
256			self.start()
257			return self
258
259			def __exit__(self, exc_type, exc_val, exc_tb):
260			self.terminate()
261
262			def __del__(self):
263			self.terminate()
264
265			def execute(self, *params):
266			"""Execute the given batch of parameters with ``exiftool``.
267
268			This method accepts any number of parameters and sends them to
269			the attached ``exiftool`` process. The process must be
270			running, otherwise ``ValueError`` is raised. The final
271			``-execute`` necessary to actually run the batch is appended
272			automatically; see the documentation of :py:meth:`start()` for
273			the common options. The ``exiftool`` output is read up to the
274			end-of-output sentinel and returned as a raw ``bytes`` object,
275			excluding the sentinel.
276
277			The parameters must also be raw ``bytes``, in whatever
278			encoding exiftool accepts. For filenames, this should be the
279			system's filesystem encoding.
280
281			.. note:: This is considered a low-level method, and should
282			rarely be needed by application developers.
283			"""
284			if not self.running:
285			raise ValueError("ExifTool instance not running.")
286			self._process.stdin.write(b"\n".join(params + (b"-execute\n",)))
287			self._process.stdin.flush()
288			output = b""
289			fd = self._process.stdout.fileno()
290			while not output[-32:].strip().endswith(sentinel):
291			output += os.read(fd, block_size)
292			return output.strip()[:-len(sentinel)]
293
294			def execute_json(self, *params):
295			"""Execute the given batch of parameters and parse the JSON output.
296
297			This method is similar to :py:meth:`execute()`. It
298			automatically adds the parameter ``-j`` to request JSON output
299			from ``exiftool`` and parses the output. The return value is
300			a list of dictionaries, mapping tag names to the corresponding
301			values. All keys are Unicode strings with the tag names
302			including the ExifTool group name in the format <group>:<tag>.
303			The values can have multiple types. All strings occurring as
304			values will be Unicode strings. Each dictionary contains the
305			name of the file it corresponds to in the key ``"SourceFile"``.
306
307			The parameters to this function must be either raw strings
308			(type ``str`` in Python 2.x, type ``bytes`` in Python 3.x) or
309			Unicode strings (type ``unicode`` in Python 2.x, type ``str``
310			in Python 3.x). Unicode strings will be encoded using
311			system's filesystem encoding. This behaviour means you can
312			pass in filenames according to the convention of the
313			respective Python version – as raw strings in Python 2.x and
314			as Unicode strings in Python 3.x.
315			"""
316			params = map(fsencode, params)
317			# Some latin bytes won't decode to utf-8.
318			# Try utf-8 and fallback to latin.
319			# http://stackoverflow.com/a/5552623/1318758
320			# https://github.com/jmathai/elodie/issues/127
321			try:
322			return json.loads(self.execute(b"-j", *params).decode("utf-8"))
323			except UnicodeDecodeError as e:
324			return json.loads(self.execute(b"-j", *params).decode("latin-1"))
325
326			def get_metadata_batch(self, filenames):
327			"""Return all meta-data for the given files.
328
329			The return value will have the format described in the
330			documentation of :py:meth:`execute_json()`.
331			"""
332			return self.execute_json(*filenames)
333
334			def get_metadata(self, filename):
335			"""Return meta-data for a single file.
336
337			The returned dictionary has the format described in the
338			documentation of :py:meth:`execute_json()`.
339			"""
340			return self.execute_json(filename)[0]
341
342			def get_tags_batch(self, tags, filenames):
343			"""Return only specified tags for the given files.
344
345			The first argument is an iterable of tags. The tag names may
346			include group names, as usual in the format <group>:<tag>.
347
348			The second argument is an iterable of file names.
349
350			The format of the return value is the same as for
351			:py:meth:`execute_json()`.
352			"""
353			# Explicitly ruling out strings here because passing in a
354			# string would lead to strange and hard-to-find errors
355			if isinstance(tags, basestring):
356			raise TypeError("The argument 'tags' must be "
357			"an iterable of strings")
358			if isinstance(filenames, basestring):
359			raise TypeError("The argument 'filenames' must be "
360			"an iterable of strings")
361			params = ["-" + t for t in tags]
362			params.extend(filenames)
363			return self.execute_json(*params)
364
365			def get_tags(self, tags, filename):
366			"""Return only specified tags for a single file.
367
368			The returned dictionary has the format described in the
369			documentation of :py:meth:`execute_json()`.
370			"""
371			return self.get_tags_batch(tags, [filename])[0]
372
373			def get_tag_batch(self, tag, filenames):
374			"""Extract a single tag from the given files.
375
376			The first argument is a single tag name, as usual in the
377			format <group>:<tag>.
378
379			The second argument is an iterable of file names.
380
381			The return value is a list of tag values or ``None`` for
382			non-existent tags, in the same order as ``filenames``.
383			"""
384			data = self.get_tags_batch([tag], filenames)
385			result = []
386			for d in data:
387			d.pop("SourceFile")
388			result.append(next(iter(d.values()), None))
389			return result
390
391			def get_tag(self, tag, filename):
392			"""Extract a single tag from a single file.
393
394			The return value is the value of the specified tag, or
395			``None`` if this tag was not found in the file.
396			"""
397			return self.get_tag_batch(tag, [filename])[0]
398
399			def set_tags_batch(self, tags, filenames):
400			"""Writes the values of the specified tags for the given files.
401
402			The first argument is a dictionary of tags and values. The tag names may
403			include group names, as usual in the format <group>:<tag>.
404
405			The second argument is an iterable of file names.
406
407			The format of the return value is the same as for
408			:py:meth:`execute()`.
409
410			It can be passed into `check_ok()` and `format_error()`.
411			"""
412			# Explicitly ruling out strings here because passing in a
413			# string would lead to strange and hard-to-find errors
414			if isinstance(tags, basestring):
415			raise TypeError("The argument 'tags' must be dictionary "
416			"of strings")
417			if isinstance(filenames, basestring):
418			raise TypeError("The argument 'filenames' must be "
419			"an iterable of strings")
420
421			params = []
422			params_utf8 = []
423			for tag, value in tags.items():
424			params.append(u'-%s=%s' % (tag, value))
425
426			params.extend(filenames)
427			params_utf8 = [x.encode('utf-8') for x in params]
428			return self.execute(*params_utf8)
429
430			def set_tags(self, tags, filename):
431			"""Writes the values of the specified tags for the given file.
432
433			This is a convenience function derived from `set_tags_batch()`.
434			Only difference is that it takes as last arugemnt only one file name
435			as a string.
436			"""
437			return self.set_tags_batch(tags, [filename])
438
439			def set_keywords_batch(self, mode, keywords, filenames):
440			"""Modifies the keywords tag for the given files.
441
442			The first argument is the operation mode:
443			KW_REPLACE: Replace (i.e. set) the full keywords tag with `keywords`.
444			KW_ADD: Add `keywords` to the keywords tag.
445			If a keyword is present, just keep it.
446			KW_REMOVE: Remove `keywords` from the keywords tag.
447			If a keyword wasn't present, just leave it.
448
449			The second argument is an iterable of key words.
450
451			The third argument is an iterable of file names.
452
453			The format of the return value is the same as for
454			:py:meth:`execute()`.
455
456			It can be passed into `check_ok()` and `format_error()`.
457			"""
458			# Explicitly ruling out strings here because passing in a
459			# string would lead to strange and hard-to-find errors
460			if isinstance(keywords, basestring):
461			raise TypeError("The argument 'keywords' must be "
462			"an iterable of strings")
463			if isinstance(filenames, basestring):
464			raise TypeError("The argument 'filenames' must be "
465			"an iterable of strings")
466
467			params = []
468
469			kw_operation = {KW_REPLACE:"-%s=%s",
470			KW_ADD:"-%s+=%s",
471			KW_REMOVE:"-%s-=%s"}[mode]
472
473			kw_params = [ kw_operation % (KW_TAGNAME, w) for w in keywords ]
474
475			params.extend(kw_params)
476			params.extend(filenames)
477			logging.debug (params)
478			return self.execute(*params)
479
480			def set_keywords(self, mode, keywords, filename):
481			"""Modifies the keywords tag for the given file.
482
483			This is a convenience function derived from `set_keywords_batch()`.
484			Only difference is that it takes as last argument only one file name
485			as a string.
486			"""
487			return self.set_keywords_batch(mode, keywords, [filename])
488

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