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There are two steps which need to be performed in order to get access to ipsana. The first step is to this API:

1. obtain and properly configure your UNIX account at PCDS. Specific instructions can be found in the Account Setup section of the Analysis Workbook.

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1. select the latest analysis release by running the following command before launching the Python interpreter:

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   % sit_setup ana-current

The later command should be done just once per an interactive session. It will initialize all relevant environment variables which are needed to run ipsana, including PATH, LD_LIBRARY_PATH, PYTHONPATH and some others. This will also give you an access to an appropriate version of the Python interpreter and the corresponding Python modules. We recommend using ipython. The following example shows illustrates how to launch the interpreter and test if the interactive psana module is available in the session environment. When everything is set up correctly one should see:

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The first application

Here is the ipsana psana version of the traditional "Hello World!" program:

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• the DAQ system may produce more than one object for a particular detector, each of which would needed to be unambiguously identified in the event container
• the external psana modules or the ipsana user's interactive Python code may add more versions for the same detector object as a result of data processing (calibration, etc.)

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• the last component (the one which has type=None) reported by the keys() method should be ignored. This is an artifact of the current implementation of ipsanathis API. It may go away in some future release of the software. We mention it here just to address possible confusion which users may have when seeing this output.
• note the variations in the syntax of the components' addresses.

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Any form of direct access would require to have an index for all objects recorded within a run. The index would complement the (purely) sequential structure of the XTC files. This feature is presently under design. It may appear in some later release of the software. And this will happen the API will be extended with additional methods allowing to address and fetch (with very little overhead) a particular event without needed to iterate over prior events.

Exchanging generic objects (of any types) between external psana modules and

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Python code

Some of our readers may not even recognize that such problem exists, and what it means. In order to illustrate it, consider the following scenario:

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