`set_major_locator` removes x-ticks (and labels) from previous subplots?

Question

I ran into this strange problem with using set_major_locator() , when using subplots which have different x-axis limits. A minimal example:

import matplotlib.pyplot as pl
import matplotlib.dates as mdates
from datetime import datetime

h24 = mdates.HourLocator(interval=24)
fmt = mdates.DateFormatter('%d-%m %H:%M')

start1 = datetime(year=2016, month=7, day=7, hour=0)
end1   = datetime(year=2016, month=7, day=9, hour=0)

start2 = datetime(year=2016, month=9, day=30, hour=0)
end2   = datetime(year=2016, month=10, day=2, hour=0)

start3 = datetime(year=2016, month=5, day=8,  hour=0)
end3   = datetime(year=2016, month=5, day=10, hour=0)

pl.figure(figsize=(9,3))

ax=pl.subplot(131)
ax.set_xlim(start1, end1)
ax.xaxis.set_major_locator(h24)
ax.xaxis.set_major_formatter(fmt)

ax=pl.subplot(132)
ax.set_xlim(start2, end2)
ax.xaxis.set_major_locator(h24)
ax.xaxis.set_major_formatter(fmt)

ax=pl.subplot(133)
ax.set_xlim(start3, end3)
ax.xaxis.set_major_locator(h24)
ax.xaxis.set_major_formatter(fmt)

pl.tight_layout()

Which results in:

If I set the x-limit of all sub-plots the same (using in this case ax.set_xlim(start1, end1) for all sub-plots) it works as expected:

Also, leaving the different set_xlim() 's and removing the set_major_locator() and set_major_formatter() lines works (although I get unreadable x-labels in this case..):

Am I making a silly mistake somewhere, or are the missing x-ticks and labels in my first example a bug in Matplotlib?

ps Matplotlib 3.0.2, Python 3.7.2

Answer 1

As of current versions of matplotlib you cannot reuse the same ticker and formatter for dates on several axes. So you need one locator and one formatter per axes .

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
from datetime import datetime


def fmt_xaxes(ax):
    h24 = mdates.HourLocator(interval=24)
    fmt = mdates.DateFormatter('%d-%m %H:%M')
    ax.xaxis.set_major_locator(h24)
    ax.xaxis.set_major_formatter(fmt)


start1 = datetime(year=2016, month=7, day=7, hour=0)
end1   = datetime(year=2016, month=7, day=9, hour=0)

start2 = datetime(year=2016, month=9, day=30, hour=0)
end2   = datetime(year=2016, month=10, day=2, hour=0)

start3 = datetime(year=2016, month=5, day=8,  hour=0)
end3   = datetime(year=2016, month=5, day=10, hour=0)


fig, (ax1, ax2, ax3) = plt.subplots(ncols=3, figsize=(9,3))


ax1.set_xlim(start1, end1)
fmt_xaxes(ax1)

ax2.set_xlim(start2, end2)
fmt_xaxes(ax2)

ax3.set_xlim(start3, end3)
fmt_xaxes(ax3)

plt.tight_layout()
plt.show()