path : a tensorboard file OR a directory, where we will find all TB files
           of the form events.*

def read_tb(path):
    """
    path : a tensorboard file OR a directory, where we will find all TB files
           of the form events.*
    """
    import pandas
    import numpy as np
    from glob import glob
    from collections import defaultdict
    import tensorflow as tf
    if osp.isdir(path):
        fnames = glob(osp.join(path, "events.*"))
    elif osp.basename(path).startswith("events."):
        fnames = [path]
    else:
        raise NotImplementedError("Expected tensorboard file or directory containing them. Got %s"%path)
    tag2pairs = defaultdict(list)
    maxstep = 0
    for fname in fnames:
        for summary in tf.train.summary_iterator(fname):
            if summary.step > 0:
                for v in summary.summary.value:
                    pair = (summary.step, v.simple_value)
                    tag2pairs[v.tag].append(pair)
                maxstep = max(summary.step, maxstep)
    data = np.empty((maxstep, len(tag2pairs)))
    data[:] = np.nan
    tags = sorted(tag2pairs.keys())
    for (colidx,tag) in enumerate(tags):
        pairs = tag2pairs[tag]
        for (step, value) in pairs:
            data[step-1, colidx] = value
    return pandas.DataFrame(data, columns=tags)