cx_oracle 5.2.1 setup.py如何自动找到其构建依赖项？

Question

I downloaded cx_oracle 5.2.1 and started building :

  python setup.py build

I noticed that it found build dependencies within my system without any specification from me. I would like to better understand how it did that. The contents in setup.py does not indicate any such information.

Answer 1

I don't have the source of cx_Oracle's setup.py in front of me right now, but in the BUILD.txt file included with it, it mentions use of some environment variables:

It is necessary to set environment variables ORACLE_HOME and LD_LIBRARY_PATH inside $HOME/.profile in order for cx_Oracle to import properly after installation and in order to build correctly. Using a text editor add the settings below to $HOME/.profile making sure to change the location of your actual installation path.

 Example ($HOME/.profile): ------------------------- export ORACLE_HOME=[your installation path]/instantclient_11_1 export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$ORACLE_HOME 

This from the section for Linux hints, as I recall I had to set the same things up to build it under Windows.

As for how it finds more standard libraries. I think that's part of the magic of the distutils module. Under unix distutils seems to generally just work so long as the required libraries and headers have been installed through your unix's standard packaging mechanism. This is probably due to the fact that unix has better standardized ways of locating build resources (than for example Windows does).

I know when I'm forced to compile Python packages under Windows, I often have to explicitly tell it where to find header files and libraries. After having had to go out and find said libraries and compile them manually.