ModuleNotFoundError：No module name '_bz2'

现象

[root@ocr]# python3.6 server.py 
Traceback (most recent call last):
  File "server.py", line 6, in <module>
    from image_preprocessing import *
  File "/home/lp/iocr-kit-core-release-1.5/image_preprocessing.py", line 6, in <module>
    from model_info import model_size
  File "/home/lp/iocr-kit-core-release-1.5/model_info.py", line 2, in <module>
    import pandas as pd
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/__init__.py", line 52, in <module>
    from pandas.core.api import (
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/core/api.py", line 29, in <module>
    from pandas.core.groupby import Grouper, NamedAgg
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/core/groupby/__init__.py", line 1, in <module>
    from pandas.core.groupby.generic import DataFrameGroupBy, NamedAgg, SeriesGroupBy
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/core/groupby/generic.py", line 57, in <module>
    from pandas.core.aggregation import (
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/core/aggregation.py", line 27, in <module>
    from pandas.core.series import FrameOrSeriesUnion, Series
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/core/series.py", line 68, in <module>
    from pandas.core import algorithms, base, generic, nanops, ops
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/core/generic.py", line 102, in <module>
    from pandas.io.formats import format as fmt
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/io/formats/format.py", line 71, in <module>
    from pandas.io.common import stringify_path
  File "/usr/local/python3.6.9/lib/python3.6/site-packages/pandas/io/common.py", line 3, in <module>
    import bz2
  File "/usr/local/python3.6.9/lib/python3.6/bz2.py", line 23, in <module>
    from _bz2 import BZ2Compressor, BZ2Decompressor
ModuleNotFoundError: No module named '_bz2'

解决

报错显示缺少 _bz2 这个 module，其实就是缺少了_bz2.cpython-36m-x86_64-linux-gnu.so 文件。报这个错的原因通常是系统装了多个 Python 环境，然后 bz2 只装到了一个环境下面，所以找不到。

1. 确保安装了对应的库

   # Ubuntu
   sudo apt-get install bzip2-devel 
   # CentOS
   sudo yum install bzip2-devel

2. 首先在本地的linux环境搜索是否存在这个文件，如果没有就到网上下载一个。

   find / -name _bz2.cpython-37m-x86_64-linux-gnu.so  # “-37m”对应的是python3.7版本

3. 把这个文件保存到你的 Python 的安装目录 /you_python_path/lib/python3.6/lib-dynload/ 文件夹下，然后将”-37m”修改为”-36m”即可。

   cd /you_python_path/lib/python3.6/lib-dynload/
   cp /usr/lib/python3.6/lib-dynload/_bz2.cpython-37m-x86_64-linux-gnu.so ./
   sudo mv _bz2.cpython-37m-x86_64-linux-gnu.so _bz2.cpython-36m-x86_64-linux-gnu.so

注：python36和37的可以互换，但是和39的不互通，所以如果缺python39的最好是到网上找一个。