84 lines
2.6 KiB
ReStructuredText
84 lines
2.6 KiB
ReStructuredText
Transformations
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===============
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.. warning::
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This is a "future" document, that does not exist, it's only kept here not to lose the data until we organize better
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documentation versioning.
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Output
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------
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Let's see the rules (first to match wins).
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1. A flag, eventually followed by something else, marks a special behaviour. If it supports it, the remaining part of
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the output line will be interpreted using the same rules, and some flags can be combined.
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**NOT_MODIFIED**
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**NOT_MODIFIED** tells bonobo to use the input row unmodified as the output.
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*CANNOT be combined*
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Example:
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.. code-block:: python
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from bonobo import NOT_MODIFIED
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def output_will_be_same_as_input(*args, **kwargs):
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yield NOT_MODIFIED
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2. Once all flags are "consumed", the remaining part is interpreted.
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* If it is a :class:`bonobo.Bag` instance, then it's used directly.
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* If it is a :class:`dict` then a kwargs-only :class:`bonobo.Bag` will be created.
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* If it is a :class:`tuple` then an args-only :class:`bonobo.Bag` will be created, unless its last argument is a
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:class:`dict` in which case a args+kwargs :class:`bonobo.Bag` will be created.
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* If it's something else, it will be used to create a one-arg-only :class:`bonobo.Bag`.
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**APPEND**
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**APPEND** tells bonobo to append this output to the input (positional arguments will equal `input_args + output_args`,
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keyword arguments will equal `{**input_kwargs, **output_kwargs}`).
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*CAN be combined, but not with itself*
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.. code-block:: python
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from bonobo import APPEND
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def output_will_be_appended_to_input(*args, **kwargs):
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yield APPEND, 'foo', 'bar', {'eat_at': 'joe'}
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**LOOPBACK**
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**LOOPBACK** tells bonobo that this output must be looped back into our own input queue, allowing to create the stream
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processing version of recursive algorithms.
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*CAN be combined, but not with itself*
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.. code-block:: python
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from bonobo import LOOPBACK
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def output_will_be_sent_to_self(*args, **kwargs):
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yield LOOPBACK, 'Hello, I am the future "you".'
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**CHANNEL(...)**
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**CHANNEL(...)** tells bonobo that this output does not use the default channel and is routed through another path.
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This is something you should probably not use unless your data flow design is complex, and if you're not certain
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about it, it probably means that it is not the feature you're looking for.
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*CAN be combined, but not with itself*
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.. code-block:: python
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from bonobo import CHANNEL
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def output_will_be_sent_to_self(*args, **kwargs):
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yield CHANNEL("errors"), 'That is not cool.'
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