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mdates.ConciseDateFormatter() doesn't work with zero_formats parameter #15178

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fifzteen opened this issue Sep 4, 2019 · 5 comments · Fixed by #15181
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mdates.ConciseDateFormatter() doesn't work with zero_formats parameter #15178

fifzteen opened this issue Sep 4, 2019 · 5 comments · Fixed by #15181
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@jklymak
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topic: date handling
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v3.1.2

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@fifzteen
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fifzteen commented Sep 4, 2019

Bug report

Bug summary

mdates.ConciseDateFormatter() raises TypeError when giving zero_formats parameter.

Code for reproduction

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import numpy as np

ny = 2
xmin, xmax = mdates.datestr2num(['2019-09-04 00:00:00', '2019-09-05 00:00:00'])
data = np.random.random((ny, int(xmax-xmin)+1))

fig, ax = plt.subplots()
ax.imshow(data, extent=[xmin, xmax, 0, ny], aspect='auto')
xlocator = mdates.AutoDateLocator()
ax.xaxis.set_major_locator(xlocator)
ax.xaxis.set_major_formatter(mdates.ConciseDateFormatter(xlocator, zero_formats=['', '%Y', '%m', '%m-%d', '%H:%M', '%H:%M']))
plt.show()

Actual outcome

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Users\foobar\AppData\Local\Programs\Python\Python37\lib\site-packages\matplotlib\dates.py", line 842, in __init__
    if len(formats) != 6:
TypeError: object of type 'NoneType' has no len()

Expected

dates.py around line 842 below.

841 if zero_formats:
842    if len(formats) != 6:
843        raise ValueError('zero_formats argument must be a list of '
844                                  '6 format strings (or None)')
845    self.zero_formats = zero_formats

now, formats is None (dafeult value). so, line 842 shuold be

842    if len(zero_formats) != 6:

Matplotlib version

  • Operating system: Windows 10
  • Matplotlib version: 3.1.1
  • Python version: 3.7.4
@jklymak
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jklymak commented Sep 4, 2019

Hah I just copied that code over. I had no idea what zero format is. If you think it’s useful to make work with the formatter we should fix it, or if not, remove it. Feel free to make a PR if you think you understand the issue well enough, otherwise I’ll try to fix in
A few weeks. Thanks for the report

@fifzteen
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fifzteen commented Sep 4, 2019

Thanks for your reply.

I simplify abobe example code to look the problem clearly.
What I want to get is a plot like below.
Figure_1

"zero_formats" is useful to draw date and time only the time is 0:00. like this code.

import matplotlib.pyplot as plt
import matplotlib.dates as mdates
import numpy as np

ny = 2
xmin, xmax = mdates.datestr2num(['2019-09-04 00:00:00', '2019-09-05 00:00:00'])
data = np.random.random((ny, int(xmax-xmin)+1))

fig, ax = plt.subplots()
ax.imshow(data, extent=[xmin, xmax, 0, ny], aspect='auto')
xlocator = mdates.AutoDateLocator()
ax.xaxis.set_major_locator(xlocator)
ax.xaxis.set_major_formatter(mdates.ConciseDateFormatter(xlocator,
                                                         formats=['%Y', '%b', '%d', '%H:%M', '%H:%M', '%S.%f'],
                                                         zero_formats=['', '%Y', '%m', '%m-%d\n%H:%M', '%H:%M', '%H:%M'],
                                                         show_offset=False))
ax.tick_params(axis='x', labelrotation=90.)
plt.show()

(We can prevent this problem by setting formats to default value.)

I don't know how many effects to other codes are exists. so I think it's better that you fix this bug.

@jklymak
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jklymak commented Sep 4, 2019

Yeah but that’s what concisedateformatter is supposed to do automatically so I’m not sure the kwarg makes sense at all?

@jklymak
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jklymak commented Sep 4, 2019

OK, duh, I added zero_formats. Sorry, should have looked at the code. This is a definite bug. I'll fix ASAP.

@jklymak jklymak self-assigned this Sep 4, 2019
@jklymak jklymak mentioned this issue Sep 4, 2019
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@jklymak
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jklymak commented Sep 4, 2019

Thanks for the report, and sorry about my confusion above. This should be fixed in 3.1.2, in the meantime, your workaround is correct.

@QuLogic QuLogic added this to the v3.1.2 milestone Sep 7, 2019
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FIX: proper call to zero_formats jklymak/matplotlib
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