Create a histograms with time on the x-axis using arrow and matplotlib

histo_timestamps.py

#!/usr/bin/env python

import argparse
import arrow
from matplotlib import pyplot as plt
from matplotlib import dates as mdates


def get_args():
    description=('Make an histogram from a list of timestamps')
    parser = argparse.ArgumentParser(description=description)
    parser.add_argument('file', metavar='<timestamps_file>',
                        help='A file with the timestamps of ')

    args = parser.parse_args()
    return args


def convert_time(atime):
    # Convert datetime objects to Matplotlib dates.
    # https://matplotlib.org/api/dates_api.html
    return mdates.date2num(atime.datetime)


def main():
    args = get_args()

    with open(args.file) as infile:
        timestamps = [arrow.get(line.strip())
                      for line in infile.readlines()]

    start = min(timestamps).replace(hours=-1).span('hour')[0]
    end = max(timestamps).replace(hours=+1).span('hour')[1]

    # fixed bin size
    bins = [convert_time(abin)
            for abin in arrow.Arrow.range('minute', start, end)][1::30]

    fig, ax = plt.subplots()
    y, x, _ = ax.hist([convert_time(atime) for atime in timestamps],
                       bins=bins)
    
    # ax.set_xlim(convert_time(start), convert_time(end))

    # obtain the max y-value of a histogram
    # https://stackoverflow.com/questions/15558136
    print('(x_max, y_max): ({},{})'.format(x.max(), y.max()))

    # Choose your xtick format string
    years_fmt = mdates.DateFormatter('%Y-%m-%d %H:00')
    # format the ticks
    ax.xaxis.set_major_formatter(years_fmt)

    xticks = [convert_time(abin)
              for abin in arrow.Arrow.range('hour', start, end)][1::6]
    ax.set_xticks(xticks)

    ax.set_title('Submission times (fixed bin size)')
    ax.set_xlabel('Timestamp (bin size = 1h)')
    ax.set_ylabel('Count')

    # auto-rotate date labels on the x-axis
    fig.autofmt_xdate()
    plt.show()


if __name__ == '__main__':
    main()