taurus.core.util.codecs

This module contains a list of codecs for the DEV_ENCODED attribute type. All codecs are based on the pair format, data. The format is a string containing the codec signature and data is a sequence of bytes (string) containing the encoded data.

This module contains a list of codecs capable of decoding several codings like bz2, zip and json.

The CodecFactory class allows you to get a codec object for a given format and also to register new codecs. The CodecPipeline is a special codec that is able to code/decode a sequence of codecs. This way you can have codecs ‘inside’ codecs.

Example:

>>> from taurus.core.util.codecs import CodecFactory
>>> cf = CodecFactory()
>>> json_codec = cf.getCodec('json')
>>> bz2_json_codec = cf.getCodec('bz2_json')
>>> data = range(100000)
>>> f1, enc_d1 = json_codec.encode(('', data))
>>> f2, enc_d2 = bz2_json_codec.encode(('', data))
>>> print(len(enc_d1), len(enc_d2))
688890 123511
>>>
>>> f1, dec_d1 = json_codec.decode((f1, enc_d1))
>>> f2, dec_d2 = bz2_json_codec.decode((f2, enc_d2))

A Taurus related example:

>>> # automatically get the data from a DEV_ENCODED attribute
>>> import taurus
>>> from taurus.core.util.codecs import CodecFactory
>>> cf = CodecFactory()
>>> devenc_attr = taurus.Attribute('a/b/c/devenc_attr')
>>> v = devenc_attr.read()
>>> codec = CodecFactory().getCodec(v.format)
>>> f, d = codec.decode((v.format, v.value))

Classes

class BZ2Codec

A codec able to encode/decode to/from BZ2 format. It uses the bz2 module

Example:

>>> from taurus.core.util.codecs import CodecFactory

>>> # first encode something
>>> data = 100 * "Hello world\n"
>>> cf = CodecFactory()
>>> codec = cf.getCodec('bz2')
>>> format, encoded_data = codec.encode(("", data))
>>> print(len(data), len(encoded_data))
1200, 68
>>> format, decoded_data = codec.decode((format, encoded_data))
>>> print(decoded_data[20])
'Hello world\nHello wo'

(more info)

class Codec

The base class for all codecs

(more info)

class CodecFactory(*p, **k)

The singleton CodecFactory class.

To get the singleton object do:

from taurus.core.util.codecs import CodecFactory
f = CodecFactory()

The CodecFactory class allows you to get a codec object for a given format and also to register new codecs.

The CodecPipeline is a special codec that is able to code/decode a sequence of codecs. This way you can have codecs ‘inside’ codecs.

Example:

>>> from taurus.core.util.codecs import CodecFactory
>>> cf = CodecFactory()
>>> json_codec = cf.getCodec('json')
>>> bz2_json_codec = cf.getCodec('bz2_json')
>>> data = range(100000)
>>> f1, enc_d1 = json_codec.encode(('', data))
>>> f2, enc_d2 = bz2_json_codec.encode(('', data))
>>> print(len(enc_d1), len(enc_d2))
688890 123511
>>>
>>> f1, dec_d1 = json_codec.decode((f1, enc_d1))
>>> f2, dec_d2 = bz2_json_codec.decode((f2, enc_d2))

A Taurus related example:

>>> # automatically get the data from a DEV_ENCODED attribute
>>> import taurus
>>> from taurus.core.util.codecs import CodecFactory
>>> cf = CodecFactory()
>>> devenc_attr = taurus.Attribute('a/b/c/devenc_attr')
>>> v = devenc_attr.read()
>>> codec = CodecFactory().getCodec(v.format)
>>> f, d = codec.decode((v.format, v.value))

(more info)

class CodecPipeline(format)

The codec class used when encoding/decoding data with multiple encoders

Example usage:

>>> from taurus.core.util.codecs import CodecPipeline

>>> data = range(100000)
>>> codec = CodecPipeline('bz2_json')
>>> format, encoded_data = codec.encode(("", data))

# decode it
format, decoded_data = codec.decode((format, encoded_data))
print(decoded_data)

(more info)

class FunctionCodec(func_name)

A generic function codec

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class JSONCodec

A codec able to encode/decode to/from json format. It uses the json module.

Example:

>>> from taurus.core.util.codecs import CodecFactory

>>> cf = CodecFactory()
>>> codec = cf.getCodec('json')
>>>
>>> # first encode something
>>> data = { 'hello' : 'world', 'goodbye' : 1000 }
>>> format, encoded_data = codec.encode(("", data))
>>> print(encoded_data)
'{"hello": "world", "goodbye": 1000}'
>>>
>>> # now decode it
>>> format, decoded_data = codec.decode((format, encoded_data))
>>> print(decoded_data)
{'hello': 'world', 'goodbye': 1000}

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class NullCodec

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class PlotCodec

A specialization of the FunctionCodec for plot function

(more info)

class Utf8Codec

A codec able to encode/decode utf8 strings to/from bytes. Useful to adapt i/o encodings in a codec pipe.

Example:

>>> from taurus.core.util.codecs import CodecFactory

>>> cf = CodecFactory()
>>> codec = cf.getCodec('zip_utf8_json')
>>>
>>> # first encode something
>>> data = { 'hello' : 'world', 'goodbye' : 1000 }
>>> format, encoded_data = codec.encode(("", data))
>>>
>>> # now decode it
>>> _, decoded_data = codec.decode((format, encoded_data))
>>> print(decoded_data)

(more info)

class ZIPCodec

A codec able to encode/decode to/from gzip format. It uses the zlib module

Example:

>>> from taurus.core.util.codecs import CodecFactory

>>> # first encode something
>>> data = 100 * "Hello world\n"
>>> cf = CodecFactory()
>>> codec = cf.getCodec('zip')
>>> format, encoded_data = codec.encode(("", data))
>>> print(len(data), len(encoded_data))
1200, 31
>>> format, decoded_data = codec.decode((format, encoded_data))
>>> print(decoded_data[20])
'Hello world\nHello wo'

(more info)