Calling Python from Seq

Calling Python from Seq 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 Seq.

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

export SEQ_PYTHON=/path/to/libpython.X.Y.so

For example, with a brew-installed Python 3.8 on macOS, this might be /usr/local/Cellar/python@3.8/3.8.8_1/Frameworks/Python.framework/Versions/3.8/lib/libpython3.8.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:

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

We can call this function in Seq using from python import:

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

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

Be sure to pass () to from python import regardless of the number of arguments the Python function takes; Seq will pass all arguments at invocation time (e.g. multiply(1, 2)). This is useful if the number of arguments to a given Python functions is variable.

@python

Seq programs can contains functions that will be executed by Python via pydef:

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

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