Python int 太大而无法转换为 C long - 绘制 Pandas 日期

Question

我已经按照本文接受的答案中显示的方法找到最近的时间戳来合并两个数据集:

pandas.merge: match the nearest time stamp >= the series of timestamps

然而，当我尝试绘制结果时，我遇到了错误:

`<matplotlib.collections.LineCollection at 0x2975a3547b8>Traceback (most recent call last):

File "C:\ProgramData\Anaconda3\lib\site-packages\IPython\core\formatters.py", line 332, in __call__
return printer(obj)

File "C:\ProgramData\Anaconda3\lib\site-packages\IPython\core\pylabtools.py", line 237, in <lambda>
png_formatter.for_type(Figure, lambda fig: print_figure(fig, 'png', **kwargs))

File "C:\ProgramData\Anaconda3\lib\site-packages\IPython\core\pylabtools.py", line 121, in print_figure
fig.canvas.print_figure(bytes_io, **kw)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\backend_bases.py", line 2208, in print_figure
**kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 507, in print_png
FigureCanvasAgg.draw(self)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\backends\backend_agg.py", line 430, in draw
self.figure.draw(self.renderer)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\figure.py", line 1295, in draw
renderer, self, artists, self.suppressComposite)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\image.py", line 138, in _draw_list_compositing_images
a.draw(renderer)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\axes\_base.py", line 2399, in draw
mimage._draw_list_compositing_images(renderer, self, artists)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\image.py", line 138, in _draw_list_compositing_images
a.draw(renderer)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\artist.py", line 55, in draw_wrapper
return draw(artist, renderer, *args, **kwargs)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\axis.py", line 1133, in draw
ticks_to_draw = self._update_ticks(renderer)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\axis.py", line 974, in _update_ticks
tick_tups = list(self.iter_ticks())

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\axis.py", line 917, in iter_ticks
majorLocs = self.major.locator()

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\dates.py", line 1054, in __call__
self.refresh()

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\dates.py", line 1074, in refresh
dmin, dmax = self.viewlim_to_dt()

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\dates.py", line 832, in viewlim_to_dt
return num2date(vmin, self.tz), num2date(vmax, self.tz)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\dates.py", line 441, in num2date
return _from_ordinalf(x, tz)

File "C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\dates.py", line 256, in _from_ordinalf
dt = datetime.datetime.fromordinal(ix).replace(tzinfo=UTC)

OverflowError: Python int too large to convert to C long

`

我从帖子中复制并粘贴了已接受的答案，但我遇到了同样的错误。

我的数据看起来像这样(它已经被合并):

cm_time_4           log_time_1
2017-06-25 10:30:35 2017-06-25 10:30:31
2017-06-25 10:50:35 2017-06-25 10:50:31
2017-06-25 11:10:35 2017-06-25 11:10:31
2017-06-25 11:30:35 2017-06-25 11:30:31
2017-06-25 11:50:35 2017-06-25 11:50:31
2017-06-25 12:10:35 2017-06-25 12:10:31
2017-06-25 12:30:35 2017-06-25 12:30:31
2017-06-25 12:50:35 2017-06-25 12:50:31
2017-06-25 13:10:35 2017-06-25 13:10:31
2017-06-25 13:30:35 2017-06-25 13:30:31
2017-06-25 13:50:35 2017-06-25 13:50:31

我的代码是这样的:

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
import scipy.io.netcdf as netcdf

readcsv = pd.read_csv(filename,parse_dates={'timestamp':['date','time']},index_col=['timestamp'])

# round off times to the nearest second
log_time = readcsv.index.round('1s')

fh = netcdf.netcdf_file(nc, mmap=False)
cm_time = fh.variables['time'][:]
ref_time = pd.datetime(year=2017, month=6, day=25, hour=10, minute=30, second=35) # Reference time
cm_time_2 = [ref_time + pd.Timedelta(minutes=np.float(i)) for i in cm_time] # Add seconds to reference time
cm_time_3 = pd.to_datetime(cm_time_2)

idx = np.searchsorted(log_time, cm_time_3) - 1
mask = idx >= 0
df = pd.DataFrame({"log_time_1":log_time[idx][mask], "cm_time_4":cm_time_3[mask]}) 

# Plot
plt.figure(figsize=(18, 4))
plt.vlines(pd.Series(log_time),0,1,colors="g")
plt.vlines(df.log_time_1, 0.3, 0.7, colors="r", lw=2)
plt.vlines(df.cm_time_4, 0.3, 0.7, colors="b", lw=2)

我在 Windows 10 上使用 python 3.6

如何解决错误？

非常感谢

Answer 1

pandas 日期时间大小为 64 位。这允许分辨率高达纳秒(默认值)的日期时间。但是，matplotlib 使用 python datetime 模块，该模块仅适用于具有毫秒分辨率并存储为 32 位的日期时间。当 matplotlib 尝试处理您的日期时，它会将它们转换为内置的 python 日期时间。此转换无法正常工作并引发异常。

因此，您需要将日期时间转换为 32 位表示形式。修改您的绘图代码:

from datetime import datetime

log_time_py = [datetime.fromtimestamp(dt.timestamp()) for dt in log_time]
log_time_1_py = [datetime.fromtimestamp(dt.timestamp()) for dt in df.log_time_1]
cm_time_4_py = [datetime.fromtimestamp(dt.timestamp()) for dt in df.cm_time_4]

# Plot
plt.figure(figsize=(18, 4))
plt.vlines(log_time_py,0,1,colors="g")
plt.vlines(log_time_1_py, 0.3, 0.7, colors="r", lw=2)
plt.vlines(cm_time_4_py, 0.3, 0.7, colors="b", lw=2)