Despite being a Lisp, Hy aims to be fully compatible with Python. That means every Python module or package can be imported in Hy code, and vice versa.
Mangling allows variable names to be spelled differently in
Hy and Python. For example, Python’s
str.format_map can be written
str.format-map in Hy, and a Hy function named
valid? would be called
is_valid in Python. You can call
hy.unmangle from either language.
Using Python from Hy¶
To use a Python module from Hy, just
import it. No additional
ceremony is required.
Using Hy from Python¶
To use a Hy module from Python, you can just
import it, provided
hy has already been imported first, whether in the current module or
in some earlier module executed by the current Python process. The
import is necessary to create the hooks that allow importing Hy modules. Note
that you can always have a wrapper Python file (such as a package’s
__init__.py) do the
import hy for the user; this is a smart thing to do
for a published package.
No way to import macros or reader macros into a Python module is implemented, since there’s no way to call them in Python anyway.
To execute Hy code from a string, use
hy.read() to convert it to
models and then
hy.eval() to evaluate it. There is no Hy
hy.eval() works even when the input
isn’t equivalent to a single Python expression.
You can use
hy.REPL.run() to launch the Hy REPL from Python, as in
hy.REPL(locals = locals()).run().
Libraries that expect Python¶
There are various means by which Hy may interact poorly with a Python library
because the library doesn’t account for the possibility of Hy. For example,
when you run hy,
sys.executable will be set to
this program rather than the original Python binary. This is helpful more often
than not, but will lead to trouble if e.g. the library tries to call
sys.executable with the
-c option. In this case, you can try
sys.executable back to
hy.sys-executable, which is a
saved copy of the original value. More generally, you can use hy2py, or you
can put a simple Python wrapper script like
import hy, my_hy_program in
front of your code.