Formatting dates python matplotlib

Question

I would like to format dates in a dates vs value plot

import datetime as datetime
from matplotlib import pyplot as pl

values = [3, 2, 5]
dates = [datetime.datetime(2014, 3, 30, 10, 56, 11, 889521),datetime.datetime(2014, 4, 1, 6, 16, 11, 889521),datetime.datetime(2014, 4, 2, 12, 16, 11, 889521)]
fig=pl.figure()
graph = fig.add_subplot(111)
graph.plot(dates,values,'k-')
pl.gcf().autofmt_xdate()
pl.show()

gives the following :

The dates are formatted '%H:%M:%S'.

How could I easily format it to '%d/%m/%Y - %H:%M:%S' ?

I have read numerous answers using num2dates and so on, but can't find a more direct way.

jmunsch · Accepted Answer · 2014-04-02 15:59:54Z

1

You can use strftime() on a datetime object.

>>> from datetime import datetime
>>> print datetime(2014,2,3,4,5,6).strftime("%d/%m/%y - %H:%M:%S")

Output:

03/02/14 - 04:05:06

answered Apr 2, 2014 at 15:59

jmunsch

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2 Comments

Jimouz Over a year ago

I used this along with xticks() and xticklabels(), the issue is, when a lot of values need to be plotted (which is my case), the x axis gets overcrowded. If I don't specify the xticks, matplotlib automatically displays only a few dates, and keeps the plot clean.

jmunsch Over a year ago

The best advice that I can give for this type of situation since I do not use matplotlib is to read the documentation on the ticker format api for matplotlib: matplotlib.org/api/ticker_api.html

RuthC · Accepted Answer · 2014-04-09 20:59:57Z

0

You could play with the value of nbins in MaxNLocator:

import matplotlib.ticker as mticker
import matplotlib.dates as mdates
fig=pl.figure()
graph = fig.add_subplot(111)
graph.plot(dates,values,'k-')
graph.xaxis.set_major_formatter(mdates.DateFormatter('%d/%m/%Y - %H:%M:%S'))
graph.xaxis.set_major_locator(mticker.MaxNLocator(nbins=5))
pl.show()

answered Apr 9, 2014 at 20:59

RuthC

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