Global Tracer Object

Some features in VizTracer require a VizTracer object so it’s helpful to make the tracer object accessible globally.

When you are using command line entry viztracer your_script.py, you don’t need to worry about it. The tracer will be automatically registered and you can access it from any file.

When you instantiate the VizTracer object like tracer = VizTracer() in your script, it will be automatically registered globally. It is not recommended to have multiple tracer objects in a single script. However, you can turn off the global register by tracer = VizTracer(register_global=False)

To access the tracer, do

from viztracer import get_tracer
# get_tracer() will return None if no tracer is registered
tracer = get_tracer()

When you use VizLoggingHandler or VizCounter or VizObject, setting their tracer to None will make the logging a NOP. This will enable you to leave the instrumentation code as it is and run your program both regularly and with viztracer

You can do things like:

from viztracer import get_tracer
from viztracer.vizlogging import VizLoggingHandler

handler = VizLoggingHandler()

handler.setTracer(get_tracer())

from viztracer import get_tracer
from viztracer.vizobject import VizObject

obj = VizObject(get_tracer(), "my variable")