Compile time preprocessor

At compile time, similar to C/C++, we have the C-preprocessor to make some decisions on what gets compiled mostly from conditionals, defines, and a mixture of both. In Cython, we can replicate some of this behavior using IF, ELIF, ELSE, and DEF. This is demonstrated as an example in the following code line:

DEF myConstant = "hello cython"

We also have access to os.uname as predefined constants from the Cython compiler:

• UNAME_SYSNAME

• UNAME_NODENAME

• UNAME_RELEASE

• UNAME_VERSION

• UNAME_MACHINE

We can also run conditional expressions against these as follows:

IF UNAME_SYSNAME == "Windows":
    include "windows.pyx"
ELSE:
    include "unix.pyx"

You also have ELIF to use in conditional expressions. If you compare something as this against some of your headers in C programs, you will see how you can replicate basic C-preprocessor behavior in Cython. This gives you a quick idea of how you can replicate C-preprocessor usage in your headers.