64 lines
2.9 KiB
ReStructuredText
64 lines
2.9 KiB
ReStructuredText
Working with files
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==================
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Bonobo would not be of any use if the aim was to uppercase small lists of strings. In fact, Bonobo should not be used
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if you don't expect any gain from parallelization/distribution of tasks.
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Let's take the following graph as an example:
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.. graphviz::
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digraph {
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rankdir = LR;
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BEGIN [shape="point"];
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BEGIN -> "A" -> "B" -> "C";
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}
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The execution strategy does a bit of under the scene work, wrapping every component in a thread (assuming you're using
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the :class:`bonobo.ThreadPoolExecutorStrategy`), which allows to start running `B` as soon as `A` yielded the first line
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of data, and `C` as soon as `B` yielded the first line of data, even if `A` or `B` still have data to yield.
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The great thing is that you generally don't have to think about it. Just be aware that your components will be run in
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parallel (with the default strategy), and don't worry too much about blocking components, as they won't block their
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siblings when run in bonobo.
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That being said, let's try to write a more real-world like transformation.
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Reading a file
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::::::::::::::
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There are a few component builders available in **Bonobo** that let you read files. You should at least know about the
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following:
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* :class:`bonobo.io.FileReader`
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* :class:`bonobo.io.JsonReader`
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* :class:`bonobo.io.CsvReader`
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Reading a file is as simple as using one of those, and for the example, we'll use a text file that was generated using
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Bonobo from the "liste-des-cafes-a-un-euro" dataset made available by Mairie de Paris under the Open Database
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License (ODbL). You can `explore the original dataset <https://opendata.paris.fr/explore/dataset/liste-des-cafes-a-un-euro/information/>`_.
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You'll need the example dataset, available in **Bonobo**'s repository.
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.. literalinclude:: ../../examples/tut02_01_read.py
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:language: python
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Until then, we ran the file directly using our python interpreter, but there is other options, one of them being
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`bonobo run`. This command allows to run a graph defined by a python file, and is replacing the :func:`bonobo.run`
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helper. It's the exact reason why we call :func:`bonobo.run` in the `if __name__ == '__main__'` block, to only
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instanciate it if it is run directly.
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Using bonobo command line has a few advantages. It will look for one and only one :class:`bonobo.Graph` instance defined
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in the file given as argument, configure an execution strategy, eventually plugins, and execute it. It has the benefit
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of allowing to tune the "artifacts" surrounding the transformation graph on command line (verbosity, plugins ...), and
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it will also ease the transition to run transformation graphs in containers, as the syntax will be the same. Of course,
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it is not required, and the containerization capabilities are provided by an optional and separate python package.
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.. code-block:: shell-session
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$ bonobo run examples/tut02_01_read.py
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