Jupyter Lab中pandas boxplot触发Matplotlib AssertionError问题

更新（2024/09/21） #

已将pd.DataFrame.boxplot替换为pd.DataFrame.plot.box函数并重启Jupyter服务器，目前可正常重复运行，未再出现此前问题。（我认为此处仍存在bug，但无需进一步帮助。）

在Jupyter Lab中执行pandas箱线图绘制命令时出现如下错误：

AssertionError                            Traceback (most recent call last)
Cell In[9], line 1
----> 1 a2_data.boxplot(column=['MinTemp', 'MaxTemp', 'Rainfall', 'Evaporation', 'WindGustSpeed', 'WindSpeed9am', 'WindSpeed3pm', 'Humidity9am', 'Humidity3pm', 'Temp9am','Temp3pm'],rot=90);

File C:\Program Files\Python312\Lib\site-packages\pandas\plotting\_core.py:533, in boxplot_frame(self, column, by, ax, fontsize, rot, grid, figsize, layout, return_type, backend, **kwargs)
    516 @Substitution(data="", backend=_backend_doc)
    517 @Appender(_boxplot_doc)
    518 def boxplot_frame(
   (...)
    530     **kwargs,
    531 ):
    532     plot_backend = _get_plot_backend(backend)
--> 533     return plot_backend.boxplot_frame(
    534         self,
    535         column=column,
    536         by=by,
    537         ax=ax,
    538         fontsize=fontsize,
    539         rot=rot,
    540         grid=grid,
    541         figsize=figsize,
    542         layout=layout,
    543         return_type=return_type,
    544         **kwargs,
    545     )

File C:\Program Files\Python312\Lib\site-packages\pandas\plotting\_matplotlib\boxplot.py:492, in boxplot_frame(self, column, by, ax, fontsize, rot, grid, figsize, layout, return_type, **kwds)
    477 def boxplot_frame(
    478     self,
    479     column=None,
   (...)
    488     **kwds,
    489 ):
    490     import matplotlib.pyplot as plt
--> 492     ax = boxplot(
    493         self,
    494         column=column,
    495         by=by,
    496         ax=ax,
    497         fontsize=fontsize,
    498         grid=grid,
    499         rot=rot,
    500         figsize=figsize,
    501         layout=layout,
    502         return_type=return_type,
    503         **kwds,
    504     )
    505     plt.draw_if_interactive()
    506     return ax

File C:\Program Files\Python312\Lib\site-packages\pandas\plotting\_matplotlib\boxplot.py:471, in boxplot(data, column, by, ax, fontsize, rot, grid, figsize, layout, return_type, **kwds)
    468     else:
    469         data = data[columns]
--> 471     result = plot_group(columns, data.values.T, ax, **kwds)
    472     ax.grid(grid)
    474 return result

File C:\Program Files\Python312\Lib\site-packages\pandas\plotting\_matplotlib\boxplot.py:414, in boxplot.<locals>.plot_group(keys, values, ax, **kwds)
    411     ax.tick_params(axis="both", labelsize=fontsize)
    413 # GH 45465: x/y are flipped when "vert" changes
--> 414 _set_ticklabels(
    415     ax=ax, labels=keys, is_vertical=kwds.get("vert", True), rotation=rot
    416 )
    417 maybe_color_bp(bp, color_tup=colors, **kwds)
    419 # Return axes in multiplot case, maybe revisit later # 985

File C:\Program Files\Python312\Lib\site-packages\pandas\plotting\_matplotlib\boxplot.py:57, in _set_ticklabels(ax, labels, is_vertical, **kwargs)
     55 if len(ticks) != len(labels):
     56     i, remainder = divmod(len(ticks), len(labels))
---> 57     assert remainder == 0, remainder
     58     labels *= i
     59 if is_vertical:

AssertionError: 3

已尝试的操作 #

• 多次重启Jupyter内核、电脑
• 切换Matplotlib后端为qt5agg（无效，已改回inline）

异常表现 #

• 仅绘制单个列时输出空白，执行a2_data.boxplot(column='Pressure9am')仅返回<Axes: >，无图像显示
• 其他pandas功能正常，仅Matplotlib相关的pandas绘图出现问题
• 此前该功能运行正常

执行代码片段 #

import pandas as pd
import numpy as np

a2_data = pd.read_csv("13545429.csv")
a2_data.sample(10)

a2_data.boxplot(column=['MinTemp', 'MaxTemp', 'Rainfall', 'Evaporation', 'WindGustSpeed', 'WindSpeed9am', 'WindSpeed3pm', 'Humidity9am', 'Humidity3pm', 'Temp9am', 'Temp3pm'],rot=90);

环境版本信息 #

INSTALLED VERSIONS
------------------
commit                : d9cdd2ee5a58015ef6f4d15c7226110c9aab8140
python                : 3.12.1.final.0
python-bits           : 64
OS                    : Windows
OS-release            : 11
Version               : 10.0.22631
machine               : AMD64
processor             : AMD64 Family 25 Model 80 Stepping 0, AuthenticAMD
byteorder             : little
LC_ALL                : None
LANG                  : None
LOCALE                : English_Australia.1252

pandas                : 2.2.2
numpy                 : 2.0.1
pytz                  : 2024.1
dateutil              : 2.9.0.post0
setuptools            : 69.0.3
pip                   : 24.2
Cython                : None
pytest                : None
hypothesis            : None
sphinx                : None
blosc                 : None
feather               : None
xlsxwriter            : None
lxml.etree            : None
html5lib              : None
pymysql               : None
psycopg2              : None
jinja2                : 3.1.4
IPython               : 8.26.0
pandas_datareader     : None
adbc-driver-postgresql: None
adbc-driver-sqlite    : None
bs4                   : 4.12.3
bottleneck            : None
dataframe-api-compat  : None
fastparquet           : None
fsspec                : None
gcsfs                 : None
matplotlib            : 3.9.2
numba                 : None
numexpr               : None
odfpy                 : None
openpyxl              : None
pandas_gbq            : None
pyarrow               : None
pyreadstat            : None
python-calamine       : None
pyxlsb                : None
s3fs                  : None
scipy                 : None
sqlalchemy            : None
tables                : None
tabulate              : None
xarray                : None
xlrd                  : 2.0.1
zstandard             : None
tzdata                : 2024.1
qtpy                  : None
pyqt5                 : None

原因与解决方法 #

该错误源于pandas箱线图绘制逻辑中的断言失败：代码假设刻度数量是标签数量的整数倍，但实际计算后余数为3，触发断言。这是pandas 2.2.2与matplotlib 3.9.2、numpy 2.0.1之间的版本兼容性bug。

有效解决方法是使用pandas推荐的新式绘图接口pd.DataFrame.plot.box替代旧的boxplot方法，修改后的代码如下：

a2_data.plot.box(column=['MinTemp', 'MaxTemp', 'Rainfall', 'Evaporation', 'WindGustSpeed', 'WindSpeed9am', 'WindSpeed3pm', 'Humidity9am', 'Humidity3pm', 'Temp9am', 'Temp3pm'], rot=90);

内容的提问来源于stack exchange，提问作者Mike C