Plot the difference in days between dates in a list

python_plot_days.py

from datetime import datetime
import matplotlib.pyplot as plt

# TODO: Use plotly instead of matplotlib
# See: https://plot.ly/python/bar-charts/

date_format = '%Y-%m-%d'

dates = []
dates.append('2016-01-01')
dates.append('2016-01-07')
dates.append('2016-01-15')
dates.append('2016-01-20')
dates.append('2016-02-01')

diffs = []

for i in range(len(dates)):
    if i < len(dates) -1:
        d0 = datetime.strptime(dates[i], date_format)
        d1 = datetime.strptime(dates[i+1], date_format)
    else:
        d0 = datetime.strptime(dates[-1], date_format)
        d1 = datetime.now()

    diff = d1 - d0
    print(diff.days)
    diffs.append(int(diff.days))

x = [diff for diff in diffs]
y = [datetime.strptime(dates[date], date_format) for date in range(len(dates))]
print(len(x), len(y))
plt.bar(y, x)
plt.title('My Title')
plt.gcf().autofmt_xdate()
plt.show()