Avoid rendering on highly frequent updates in progressbar

[tilsche]

I am using a progressbar in a loop with short iterations, which negatively affects performance. It would be good to supply a chunk size such that the heavy part of an update is only performed every nth time.

Currently I am using a small wrapper around it:

class ChunkProgressbar:
    def __init__(self, iterator, chunk_size=100, enabled=True, **kwargs):
        self.iterator = iterator
        self.chunk_size = chunk_size
        self.bar = progressbar(iterator, **kwargs)
        self.missed_updates = 0

    def __enter__(self):
        if self.bar is not None:
            self.bar.__enter__()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.bar.update(self.missed_updates)
        self.bar.__exit__(exc_type, exc_val, exc_tb)

    def __iter__(self):
        for index, elem in enumerate(self.iterator):
            yield elem
            self.missed_updates += 1
            if index % self.chunk_size == self.chunk_size - 1:
                self.bar.update(self.missed_updates)
                self.missed_updates = 0

One could also throttle the rendering based on timing information (like the eta calculation), but that might be costly again due to timing calls or mess with heterogeneous iteration times.