with probability block

probability.py

import random
import sys


class probability:
    """Based on https://stackoverflow.com/questions/12594148/skipping-execution-of-with-block"""
    def __init__(self, probability):
        assert probability >= 0 and probability <= 1
        self.probability = probability

    def __enter__(self):
        if random.random() > self.probability:
            sys.settrace(lambda *args, **keys: None)
            frame = sys._getframe(1)
            frame.f_trace = self.trace

    def trace(self, frame, event, arg):
        raise SkipWithBlock()

    def __exit__(self, type, value, traceback):
        if type is None:
            return  # No exception
        if issubclass(type, SkipWithBlock):
            return True  # Suppress special SkipWithBlock exception


class SkipWithBlock(Exception):
    pass


# Example
if __name__ == "__main__":
    for i in range(10):
        with probability(0.5):
            print(f"{i}. hello")