First Steps

When writing CSP code there will be runtime components in the form of csp.node methods, as well as graph-building components in the form of csp.graph components.

It is important to understand that csp.graph components will only be executed once at application startup in order to construct the graph. Once the graph is constructed, csp.graph code is no longer needed. Once the graph is run, only inputs, csp.nodes and outputs will be active as data flows through the graph, driven by input ticks.

For example, this is a simple bit of graph code:

import csp
from csp import ts
from datetime import datetime


@csp.node
def spread(bid: ts[float], ask: ts[float]) -> ts[float]:
    if csp.valid(bid, ask):
        return ask - bid


@csp.graph
def my_graph():
    bid = csp.const(1.0)
    ask = csp.const(2.0)
    bid = csp.multiply(bid, csp.const(4))
    ask = csp.multiply(ask, csp.const(3))
    s = spread(bid, ask)

    csp.print('spread', s)
    csp.print('bid', bid)
    csp.print('ask', ask)


if __name__ == '__main__':
    csp.run(my_graph, starttime=datetime.utcnow())

In order to help visualize this graph, you can call csp.show_graph:

The result of this would be:

2020-04-02 15:33:38.256724 bid:4.0
2020-04-02 15:33:38.256724 ask:6.0
2020-04-02 15:33:38.256724 spread:2.0