Python cx_Oracle 安装小记

SQLAlchemy 是 Python 中用来操作数据库的一个利器,支持 MySQL、Oracle、PostgreSQL、SQLite。使用 SQLAlchemy 来管理 Oracle 的数据需要安装依赖 cx_Oracle。在这过程中遇到不少问题,记录如下。

现在已经可以通过 pip install cx_Oracle 来安装

Windows

Oracle 客户端环境

因为 Oracle 需要客户端才能使用,推荐下载绿色版的 instantclient,请到 Oracle 官网下载,如果是10g或者11g,可以选择 instantclient_11_2

安装 cx_Oracle

安装 cx_Oracle 正确版本,需要区分数据库为 10g 还是 11g。然后可以从 pypi 上下载对应版本的 exe 来安装。

可能遇到的问题

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ImportError: DLL load failed: 找不到指定的模块。

将 instantclient_11_2 所在的目录添加到环境变量,但是环境变量有时没有立即生效
,可以复制 oci.dll(版本也要正确)到 \Python27\Lib\site-packages 目录下

这时又出现问题

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Unable to acquire Oracle environment handle

复制 oci.dll 依赖的 dll,oraociei11.dll,ocijdbc11.dll 到 \Python27\Lib\site-packages 目录下。如果不清楚就将 instantclient_11_2 目录下的 dll 都复制到 \Python27\Lib\site-packages 目录下

详细信息还可以参考这里

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# UNIX
libclnstsh.so.10.1
libnnz10.so
libociei.so
# Windows
oci.dll
oraociei10.dll
orannzsbb10.dll

Linux

Oracle 客户端环境

先安装 rpm

yum install rpm

下载 oracle-instantclient-basic-10.2.0.3-1.x86_64.rpm,请到 Oracle 官网下载

安装 Oracle 客户端

rpm -ivh oracle-instantclient-basic-10.2.0.3-1.x86_64.rpm

安装 cx_Oracle

先从 pypi 上下载好指定版本的 cx_Oracle,然后安装

rpm -ivh cx_Oracle-5.1.2-10g-py27-1.x86_64.rpm 

验证是否安装成功

# 有这个文件表示安装成功,根据 python 的位置,也可能在其他地方
ls /usr/lib/python2.7/site-packages/cx_Oracle.so 

可能的问题 1

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import cx_Oracle
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
ImportError: libclntsh.so.10.1: cannot open shared object file: No such file or directory

The problem is that the just installed libraries of the Oracle Instant Client aren’t part of the default library path of your CentOS installation. Either you have to extend the LD_LIBRARY_PATH Bash variable of your current user or you have to add the lib directory of the Instant Client installation to the system-wide library path if all users should be allowed to use the Oracle Instant Client. To do so you have to create a new file, e.g. oracle.conf, in the /etc/ld.so.conf.d directory with the following content:

vim /etc/ld.so.conf.d/oracle.conf

添加

/usr/lib/oracle/10.2.0.3/client64/lib/

This tells ldconfig to also look for libraries in the lib folder of the Instant Client installation. To update the library cache just call ldconfig without any parameter. This will take a while since ldconfig will re-read every configured library folder and add its content to the library cache. The new oracle.conf file has to be owned by the root user as well as ldconfig has to be called as the root user. Afterwards so should be able to use the cx_Oracle module in your Python shell:

这样做之后,有时仍然出现问题。参照这里的方法,需要设置环境变量

方法1:
export PATH
在/etc/profile文件中添加变量,该变量将会对Linux下所有用户有效,并且是“永久的”。

vi /etc/profile

在文件末尾添加

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LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/lib/oracle/10.2.0.3/client64/lib
export LD_LIBRARY_PATH

要是刚才的修改马上生效,需要执行以下代码

source /etc/profile

这时再查看系统环境变量,就能看见刚才加的东西已经生效了

echo $LD_LIBRARY_PATH

方法2: 直接运行export命令定义变量,只对当前shell(BASH)有效(临时的)

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export LD_LIBRARY_PATH=${LD_LIBRARY_PATH}:/usr/lib/oracle/10.2.0.3/client64/lib

可能的问题 2

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import cx_Oracle
ImportError: No module named cx_Oracle

如果安装的 python 64 位,需要把cx_Oracle文件复制到 /usr/lib64/python2.7/site-packages/ 目录下

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cd /usr/lib/python2.7/site-packages/
cp cx_Oracle.so /usr/lib64/python2.7/site-packages/cx_Oracle.so
cp cx_Oracle-5.1.2-py2.7.egg-info /usr/lib64/python2.7/site-packages/cx_Oracle-5.1.2-py2.7.egg-info

如果是 Ubuntu 系统则需要注意

For Debian and derivatives, this sys.path is augmented with directories for packages distributed within the distribution. Local addons go into /usr/local/lib/python/dist-packages, Debian addons install into /usr/{lib,share}/python/dist-packages. /usr/lib/python/site-packages is not used.

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cd /usr/lib/python2.7
sudo mv site-packages/cx_Oracle* dist-packages/
sudo rmdir site-packages/
sudo ln -s dist-packages site-packages
sudo ldconfig
# Thanks to http://bayo.opadeyi.net/2011/07/setting-up-cxoracle-on-ubuntu-1104.html

SQLAlchemy Oracle 的中文问题

你需要设置 NLS_LANG 环境变量,否则你读取出来的中文可能是乱码,或者当 insert 的数据有中文时会导致 Unicode 编码错误。

你可以在 Python 代码中这么设置环境变量

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# 设置编码,否则:
# 1. Oracle 查询出来的中文是乱码
# 2. 插入数据时有中文,会导致
# UnicodeEncodeError: 'ascii' codec can't encode characters in position 1-7: ordinal not in range(128)
os.environ['NLS_LANG'] = 'SIMPLIFIED CHINESE_CHINA.UTF8'