Matplotlib hangs when plotting

Question

I am trying to plot some datetime objects in Python with Matplotlib, just as I have seen at this question.

But when it gets to the savefig call, it gets stuck. This is my code:

import matplotlib as mpl
mpl.use('Agg')  # Matplotlib backend to use without an X-server
import matplotlib.pyplot as plt
from matplotlib.dates import DateFormatter, MinuteLocator
from datetime import datetime
from datetime import timedelta

def plot_scenario(outages_start, outages_end, prediction_start, prediction_end,
    filepath=None):

    fig = plt.figure()
    ax = fig.add_subplot(111)

    y = [0.3, 0.7]
    timelines(ax, y[0], prediction_start, prediction_end, color='r')
    for xstart, xstop in zip(outages_start, outages_end):
        timelines(ax, y[1], xstart, xstop)

    ax.xaxis_date()
    myFmt = DateFormatter('%d %H:%M')
    ax.xaxis.set_major_formatter(myFmt)
    ax.xaxis.set_major_locator(MinuteLocator(0, interval=15))

    # Delta needed to adjust the xlimits
    delta = (prediction_end - prediction_start) / 10

    #ax.set_yticks(['Prediction', 'Outages'])  #Not working
    ax.set_ylim(0, 1)
    ax.set_xlim(prediction_start - delta, prediction_end + delta)
    ax.set_xlabel('Time')

    if filepath is None:
        fig.show()
    else:
        # Save plot as PNG
        fig.savefig(filepath) # Gets stuck here
        print 'PGN file saved at ' + filepath


# plot timelines at y from xstart to xstop with a given color
def timelines(current_axis, y, xstart, xstop, color='b'):
    current_axis.hlines(y, xstart, xstop, color, lw=4)
    current_axis.vlines(xstart, y+0.03, y-0.03, color, lw=2)
    current_axis.vlines(xstop, y+0.03, y-0.03, color, lw=2)

if __name__ == '__main__':
    prediction_start = datetime(2014, 3, 20) + timedelta(hours=12)
    prediction_end = prediction start + timedelta(hours=10)
    outages_start = []
    outages_end = []
    outages_start.append(datetime(2014, 3, 20) + timedelta(hours=14))
    outages_end.append(datetime(2014, 3, 20) + timedelta(hours=15))
    outages_start.append(datetime(2014, 3, 20) + timedelta(hours=17))
    outages_end.append(datetime(2014, 3, 20) + timedelta(hours=18))

    path = '/home/myuser/test.png'
    plot_scenario(outages_start, outages_end, prediction_start, prediction_end, path)

I'm using Agg since I'm working without X-server into an Ubuntu Server machine, but this can't be the problem because I made a simple range plot and the figure was saved correctly, so I must be making some mistake at the code.

Any help?

Can you try to reduce the amount of code here? Without the ability to reproduce your problem there isn't much anyone can do to help you. — tacaswell, Mar 20 '14 at 16:42
It is currently a small code, just the main is missing, so I don't know what the problem is, or why I'm deserving a downvote. I'll add the main anyway — Roman Rdgz, Mar 20 '14 at 16:55
The problem isn't length, it is that it is not runnable. http://www.sscce.org/ — tacaswell, Mar 20 '14 at 16:57
And you got a down vote because you have enough rep to know better. — tacaswell, Mar 20 '14 at 16:58

score 1 · Accepted Answer · answered Mar 25 '14 at 08:05

1

Looks like the problem is in the line:

ax.xaxis.set_major_locator(MinuteLocator(0, interval=15))

But I don't really know why. Commenting that line, the code works.

answered Mar 25 '14 at 08:05

Roman Rdgz

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Matplotlib hangs when plotting

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