在Jupyter Notebook中用rpy2与R Magic加载R库时遇值错误

问题场景 #

在Jupyter Notebook中使用%%R魔法命令加载多个R包时触发错误，代码如下：

%%R 
# Load libraries from correct lib Paths for my environment - ignore this!
 .libPaths(.libPaths()[c(3,2,1)])

# Load all the R libraries we will be using in the notebook

library(scran)
library(RColorBrewer)
library(slingshot)
library(monocle)
library(gam)
library(BiocParallel)
library(ggplot2)
library(plyr)
library(MAST)

错误信息 #

---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
File /opt/anaconda3/envs/tsc-env/lib/python3.9/site-packages/rpy2/rinterface_lib/conversion.py:179, in _get_cdata(obj)
    178 try:
--> 179     cdata = obj.__sexp__._cdata
    180 except AttributeError:

AttributeError: 'numpy.str_' object has no attribute '__sexp__'

During handling of the above exception, another exception occurred:

ValueError                                Traceback (most recent call last)
Cell In[5], line 1
----> 1 get_ipython().run_cell_magic('R', '', '# Load libraries from correct lib Paths for my environment - ignore this!\n .libPaths(.libPaths()[c(3,2,1)])\n\n# Load all the R libraries we will be using in the notebook\n\nlibrary(scran)\nlibrary(RColorBrewer)\nlibrary(slingshot)\nlibrary(monocle)\nlibrary(gam)\nlibrary(BiocParallel)\nlibrary(ggplot2)\nlibrary(plyr)\nlibrary(MAST)\n#library(Seurat)\n#library(scater)\n#library(scDblFinder)\n#library(sctransform)\n#library(scry)\n#library(clusterExperiment)\n')

File /opt/anaconda3/envs/tsc-env/lib/python3.9/site-packages/IPython/core/interactiveshell.py:2517, in InteractiveShell.run_cell_magic(self, magic_name, line, cell)
   2515 with self.builtin_trap:
   2516     args = (magic_arg_s, cell)
--> 2517     result = fn(*args, **kwargs)
   2519 # The code below prevents the output from being displayed
   2520 # when using magics with decorator @output_can_be_silenced
   2521 # when the last Python token in the expression is a ';'.
   2522 if getattr(fn, magic.MAGIC_OUTPUT_CAN_BE_SILENCED, False):

File /opt/anaconda3/envs/tsc-env/lib/python3.9/site-packages/rpy2/ipython/rmagic.py:935, in RMagics.R(self, line, cell, local_ns)
...
    182                          'to map it to one: %s' % repr(obj))
    183 else:
    184     cdata = cls(obj)

ValueError: Not an rpy2 R object and unable to map it to one: np.str_('value')

解决方案 #

以下是几种可行的修复方法，按优先级尝试：

1. 禁用rpy2的自动类型转换 #

这个错误的核心是rpy2在转换R输出到Python对象时，误处理numpy字符串类型导致的。可以通过两种方式禁用自动转换：

• 方式一：给R魔法命令加-n参数
  修改代码为：

  %%R -n
  .libPaths(.libPaths()[c(3,2,1)])
  library(scran)
  library(RColorBrewer)
  library(slingshot)
  library(monocle)
  library(gam)
  library(BiocParallel)
  library(ggplot2)
  library(plyr)
  library(MAST)
  

  -n参数表示不进行R与Python对象的自动转换，规避类型转换错误。

• 方式二：全局禁用转换
  在运行%%R代码前，先执行以下Python代码：

  import rpy2.robjects as ro
  ro.conversion.set_default_conversion(ro.conversion.get_conversion())
  

2. 调整.libPaths()的使用方式 #

避免动态排序.libPaths的返回值，改为直接指定明确的库路径。先查看当前库路径：

%%R
print(.libPaths())

再将输出的路径按需求手动写入：

%%R
.libPaths(c("/path/to/your/lib3", "/path/to/your/lib2", "/path/to/your/lib1"))
# 后续加载包代码不变

3. 排查冲突的R包 #

逐个加载包，定位触发问题的包：

%%R -n
.libPaths(.libPaths()[c(3,2,1)])
library(scran)  # 运行无错误后再加载下一个包

找到问题包后，可尝试加载时抑制输出：library(package, quietly=TRUE)。

4. 修复版本兼容性 #

该错误常出现在rpy2 3.x与高版本numpy（如1.24+）的组合中，可降级指定兼容版本：

pip install numpy==1.23.5 rpy2==3.5.1

安装完成后重启Jupyter内核。

5. 重置Jupyter环境 #

重启Jupyter Notebook内核，清除环境残留后重新运行加载包代码。

内容的提问来源于stack exchange，提问作者Skim