Calling Python from Codon is possible in two ways:

-   `from python import` allows importing and calling Python functions
    from existing Python modules.
-   `@python` allows writing Python code directly in Codon.

In order to use these features, the `CODON_PYTHON` environment variable
must be set to the appropriate Python shared library:

``` bash
export CODON_PYTHON=/path/to/libpython.X.Y.so
```

For example, with a `brew`-installed Python 3.9 on macOS, this might be

``` bash
/usr/local/opt/python@3.9/Frameworks/Python.framework/Versions/3.9/lib/libpython3.9.dylib
```

Note that only Python versions 3.6 and later are supported.

# `from python import`

Let\'s say we have a Python function defined in *mymodule.py*:

``` python
def multiply(a, b):
    return a * b
```

We can call this function in Codon using `from python import` and
indicating the appropriate call and return types:

``` python
from python import mymodule.multiply(int, int) -> int
print(multiply(3, 4))  # 12
```

(Be sure the `PYTHONPATH` environment variable includes the path of
*mymodule.py*!)

# `@python`

Codon programs can contain functions that will be executed by Python via
`pydef`:

``` python
@python
def multiply(a: int, b: int) -> int:
    return a * b

print(multiply(3, 4))  # 12
```

This makes calling Python modules like NumPy very easy:

``` python
@python
def myrange(n: int) -> List[int]:
    from numpy import arange
    return list(arange(n))

print(myrange(5))  # [0, 1, 2, 3, 4]
```