Introduction ============ Orca is a Python library specifically designed for backtesting **statistical arbitrage** strategies(*"alpha"* henceforth) on China A-Shares market. This library is integrated with a delibrately structured **MongoDB** as its data source. It depends heavily on the high-performance Python library `Pandas `_, thus it is recommended to get familiar with its basic data structures(Series, DataFrame, Panel). To experiment with Orca, it is advised that one creates a virtual Python environment with :program:`virtualenv`:: $virtualenv /your/local/directory and install the following dependency libraries properly: * `Pandas `_ * `PyMongo `_ * `PyTables `_ * `TA-Lib `_ Orca has 9 main components: * MongoDB interface * Data cache * Alphas * Operations * Performance * Universes * Utilities * Updaters * Alpha DB interface For backtesting purpose, one only have to focus on the first 7 components which are explained in detail in this documentation.