导入HH：MM：SS时间值导致＆＃34;格式字符串无效＆＃34;使用plot_date时

Question

我一直在尝试使用格式为HH：MM：SS的x轴制作一个简单的图，其中的值取自相同格式的文件。我正在使用numpy.loadtxt和转换器来读取时间和值，如下所示：

time, moisture = np.loadtxt(dirlist[0], usecols=(1,2), unpack=True, converters = {1: dates.strpdate2num("%H:%M:%S")})

但是，当我使用date_plot绘图时，收到以下错误：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python27\lib\lib-tk\Tkinter.py", line 1486, in __call__
    return self.func(*args)
  File "C:\Python27\lib\site-packages\matplotlib\backends\backend_tkagg.py", line 276, in resize
    self.show()
  File "C:\Python27\lib\site-packages\matplotlib\backends\backend_tkagg.py", line 348, in draw
    FigureCanvasAgg.draw(self)
  File "C:\Python27\lib\site-packages\matplotlib\backends\backend_agg.py", line 451, in draw
    self.figure.draw(self.renderer)
  File "C:\Python27\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\figure.py", line 1034, in draw
    func(*args)
  File "C:\Python27\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\axes.py", line 2086, in draw
    a.draw(renderer)
  File "C:\Python27\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
    draw(artist, renderer, *args, **kwargs)
  File "C:\Python27\lib\site-packages\matplotlib\axis.py", line 1091, in draw
    ticks_to_draw = self._update_ticks(renderer)
  File "C:\Python27\lib\site-packages\matplotlib\axis.py", line 945, in _update_ticks
    tick_tups = [t for t in self.iter_ticks()]
  File "C:\Python27\lib\site-packages\matplotlib\axis.py", line 893, in iter_ticks
    for i, val in enumerate(majorLocs)]
  File "C:\Python27\lib\site-packages\matplotlib\dates.py", line 524, in __call__
    return self._formatter(x, pos)
  File "C:\Python27\lib\site-packages\matplotlib\dates.py", line 375, in __call__
    return self.strftime(dt, self.fmt)
  File "C:\Python27\lib\site-packages\matplotlib\dates.py", line 413, in strftime
    s1 = time.strftime(fmt, (year,) + timetuple[1:])
ValueError: Invalid format string

在我看来它抱怨失踪的一年时，我决定使用num2date检查解析的日期，并返回1900-01-01 11:10:41+00:00的正确日期，但我不知道为什么会有+00:00。这可能是我困境的根源吗？

即使strpdate2num正确解析，我决定检查是否在文件中的时间开头添加YYYY:MM:DD它是否正常工作并且低并且看到它。不幸的是，我宁愿不在每个时间值的开头添加YYYY:MM:DD，所以最后我的问题是：如何在没有YYYY:MM:DD前缀的情况下阅读时如何使plot_date工作？为什么strpdate2num是不是要照顾这个？

干杯， 戴夫

根据要求，输入文件的片段：

0.465752314814815   11:10:41    9.086096129
0.466226851851852   11:11:22    8.346124754
0.466701388888889   11:12:03    8.179795013
0.467175925925926   11:12:44    8.364891272
0.467662037037037   11:13:26    8.147598262
0.468136574074074   11:14:07    8.35810013
0.468611111111111   11:14:48    8.333816653
0.469085648148148   11:15:29    8.41123069
0.469085648148148   11:15:29    8.130661712
0.469560185185185   11:16:10    3.131862435

这是我的代码：

datefunc = lambda x: dates.date2num(datetime.datetime.strptime(x, '%H:%M:%S'))

times, moisture = np.loadtxt(dirlist[0], delimiter='\t', usecols=(1,2), converters={1: datefunc}, unpack=True) 

times_date=[]

for t in times:
    times_date.append(dates.num2date(t)) #Converting back to a datetime object

plt.plot_date(times_date , moisture, xdate=True)
# plt.gcf().autofmt_xdate()
plt.show()
plt.close()

Answer 1

这似乎是一个奇怪的问题，因为您的原始代码看起来不错。这在Python 2中适用于我（Python 3需要从字节数据转换）。我用你的示例数据尝试了这个：

import matplotlib.pyplot as plt
from matplotlib.dates import strpdate2num
import numpy as np

time, val = np.loadtxt("File.txt", usecols=(1,2), unpack=True, converters = {1: strpdate2num("%H:%M:%S")})

plt.plot_date(time, val)
plt.show()