otp.Source.dump#

Source.dump(label=None, where=None, columns=None, callback=None)#

Dumps the columns from ticks into std::out in runtime if they fit the where condition. Every dump has a corresponding header that always includes the TIMESTAMP field. Other fields could be configured using the columns parameter. A header could be augmented with a label parameter; this label is an addition column that helps to distinguish ticks from multiple dumps with the same schema, because ticks from different dumps could be mixed. It might happen because of the OneTick multithreading, and there is the operating system buffer between the OneTick and the actual output.

This method is helpful for debugging.

Parameters

label (str) – A label for a dump. It adds a special column _OUT_LABEL_ for all ticks and set to the specified value. It helps to distinguish ticks from multiple dumps, because actual output could contain mixed ticks due the concurrency. None means no label.
where (Operation) – A condition that allows to filter ticks to dump. None means no filtering.
columns (str, tupel or list) – List of columns that should be in the output. None means dump all columns.
callback (callable) – Callable, which preprocess source before printing.

Examples

>>> data.dump(label='Debug point', where=data['PRICE'] > 99.3, columns=['PRICE', 'QTY'])    
>>> data.dump(columns="X", callback=lambda x: x.first(), label="first")     