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Introduction

This document offers a brief overview of a high-level interface to the psana analysis framework for user applications written in the Python programming language. The interface is informally known as "interactive psana*. The tool's use is not solely limited to the interactive analysis scenarios. It also allows its users to benefit from a rich set of services of the core framework while retaining a full control over an iteration in data sets (runs, files, etc.). This combination makes it possible for the interactive exploration and (if needed) visualization of the experimental data. Note that by the later we always mean data files in the XTC or HDF5 formats produced at the LCLS DAQ or Data Management system. We also suggest visiting the Glossary of Terms which is found in the end of the document.

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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.

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Data exchange between external psana modules and 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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