Trace specific functions in Python to capture high-level execution flow

Question

Python offers tracing through its trace module. There are also custom solutions like this. But these approaches capture most low-level executions, inside-and-out of most/every library you use. Other than deep-dive debugging this isn't very useful.

It would be nice to have something that captures only the highest-level functions laid out in your pipeline. For example, if I had:

def funct1():
    res = funct2()
    print(res)

def funct2():
    factor = 3
    res = funct3(factor)
    return(res)

def funct3(factor):
    res = 1 + 100*factor
    return(res)

...and called:

funct1()

...it would be nice to capture:

function order:
    - funct1
    - funct2
    - funct3

I have looked at:

I am happy to manually mark the functions inside the scripts, like we do with Docstrings. Is there a way to add "hooks" to functions, then track them as they get called?

James · Accepted Answer · 2020-10-17 22:06:54Z

You can always use a decorator to track which functions are called. Here is an example that allows you to keep track of what nesting level the function is called at:

class Tracker:
    level = 0

    def __init__(self, indent=2):
        self.indent = indent

    def __call__(self, fn):
        def wrapper(*args, **kwargs):
            print(' '*(self.indent * self.level) + '-' + fn.__name__)
            self.level += 1
            out = fn(*args, **kwargs)
            self.level -= 1
            return out
        return wrapper


track = Tracker()

@track
def funct1():
    res = funct2()
    print(res)

@track
def funct2():
    factor = 3
    res = funct3(factor)
    return(res)

@track
def funct3(factor):
    res = 1 + 100*factor
    return(res)

It uses the class variable level to keep track of how many functions have been called and simply prints out the the function name with a space indent. So calling funct1 gives:

funct1()
# prints:
-funct1
  -funct2
    -funct3
# returns:
301

Depending on how you want to save the output, you can use the logging module for the output

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