Makefile

.PHONY: run

export JULIA_PROJECT = $(PWD)
JULIA = julia
JULIAC_PATH = $(shell $(JULIA) --startup-file=no -E 'normpath(Base.find_package("PackageCompiler"), "..", "..", "juliac.jl")')
RUN_JULIAC = $(JULIA) $(JULIAC_PATH)

run: builddir/test.so
	python test.py

builddir/test.so: test.jl
	$(JULIA) --color=yes -e "using Pkg; Pkg.instantiate()"
	$(RUN_JULIAC) -vas $<

Manifest.toml

[[ArgParse]]
deps = ["Compat", "Test", "TextWrap"]
git-tree-sha1 = "37159c768f28ae52ef9af1e70669d25a68ba7d61"
uuid = "c7e460c6-2fb9-53a9-8c5b-16f535851c63"
version = "0.6.1"

[[Base64]]
uuid = "2a0f44e3-6c83-55bd-87e4-b1978d98bd5f"

[[BinDeps]]
deps = ["Compat", "Libdl", "SHA", "URIParser"]
git-tree-sha1 = "12093ca6cdd0ee547c39b1870e0c9c3f154d9ca9"
uuid = "9e28174c-4ba2-5203-b857-d8d62c4213ee"
version = "0.8.10"

[[BinaryProvider]]
deps = ["Libdl", "Pkg", "SHA", "Test"]
git-tree-sha1 = "9930c1a6cd49d9fcd7218df6be417e6ae4f1468a"
uuid = "b99e7846-7c00-51b0-8f62-c81ae34c0232"
version = "0.5.2"

[[BufferedStreams]]
deps = ["Compat", "Test"]
git-tree-sha1 = "5d55b9486590fdda5905c275bb21ce1f0754020f"
uuid = "e1450e63-4bb3-523b-b2a4-4ffa8c0fd77d"
version = "1.0.0"

[[Compat]]
deps = ["Base64", "Dates", "DelimitedFiles", "Distributed", "InteractiveUtils", "LibGit2", "Libdl", "LinearAlgebra", "Markdown", "Mmap", "Pkg", "Printf", "REPL", "Random", "Serialization", "SharedArrays", "Sockets", "SparseArrays", "Statistics", "Test", "UUIDs", "Unicode"]
git-tree-sha1 = "2d9e14d19bad3f9ad5cc5e4cffabc3cfa59de825"
uuid = "34da2185-b29b-5c13-b0c7-acf172513d20"
version = "1.3.0"

[[Dates]]
deps = ["Printf"]
uuid = "ade2ca70-3891-5945-98fb-dc099432e06a"

[[DelimitedFiles]]
deps = ["Mmap"]
uuid = "8bb1440f-4735-579b-a4ab-409b98df4dab"

[[Distributed]]
deps = ["LinearAlgebra", "Random", "Serialization", "Sockets"]
uuid = "8ba89e20-285c-5b6f-9357-94700520ee1b"

[[HTTPClient]]
deps = ["Compat", "LibCURL"]
git-tree-sha1 = "161d5776ae8e585ac0b8c20fb81f17ab755b3671"
uuid = "0862f596-cf2d-50af-8ef4-f2be67dfa83f"
version = "0.2.1"

[[InteractiveUtils]]
deps = ["LinearAlgebra", "Markdown"]
uuid = "b77e0a4c-d291-57a0-90e8-8db25a27a240"

[[LibCURL]]
deps = ["BinaryProvider", "Compat", "Libdl", "Printf"]
git-tree-sha1 = "6339c87cb76923a3cf947fcd213cbc364355c9c9"
uuid = "b27032c2-a3e7-50c8-80cd-2d36dbcbfd21"
version = "0.4.1"

[[LibExpat]]
deps = ["Compat"]
git-tree-sha1 = "fde352ec13479e2f90e57939da2440fb78c5e388"
uuid = "522f3ed2-3f36-55e3-b6df-e94fee9b0c07"
version = "0.5.0"

[[LibGit2]]
uuid = "76f85450-5226-5b5a-8eaa-529ad045b433"

[[Libdl]]
uuid = "8f399da3-3557-5675-b5ff-fb832c97cbdb"

[[Libz]]
deps = ["BufferedStreams", "Random", "Test"]
git-tree-sha1 = "d405194ffc0293c3519d4f7251ce51baac9cc871"
uuid = "2ec943e9-cfe8-584d-b93d-64dcb6d567b7"
version = "1.0.0"

[[LinearAlgebra]]
deps = ["Libdl"]
uuid = "37e2e46d-f89d-539d-b4ee-838fcccc9c8e"

[[Logging]]
uuid = "56ddb016-857b-54e1-b83d-db4d58db5568"

[[Markdown]]
deps = ["Base64"]
uuid = "d6f4376e-aef5-505a-96c1-9c027394607a"

[[Mmap]]
uuid = "a63ad114-7e13-5084-954f-fe012c677804"

[[PackageCompiler]]
deps = ["ArgParse", "Libdl", "Pkg", "Serialization", "SnoopCompile", "Test", "WinRPM"]
git-tree-sha1 = "58ae9646b6a25bb2ebd1ed1e74e22aa02375c3a7"
uuid = "9b87118b-4619-50d2-8e1e-99f35a4d4d9d"
version = "0.5.0"

[[Pkg]]
deps = ["Dates", "LibGit2", "Markdown", "Printf", "REPL", "Random", "SHA", "UUIDs"]
uuid = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"

[[Printf]]
deps = ["Unicode"]
uuid = "de0858da-6303-5e67-8744-51eddeeeb8d7"

[[REPL]]
deps = ["InteractiveUtils", "Markdown", "Sockets"]
uuid = "3fa0cd96-eef1-5676-8a61-b3b8758bbffb"

[[Random]]
deps = ["Serialization"]
uuid = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"

[[SHA]]
uuid = "ea8e919c-243c-51af-8825-aaa63cd721ce"

[[Serialization]]
uuid = "9e88b42a-f829-5b0c-bbe9-9e923198166b"

[[SharedArrays]]
deps = ["Distributed", "Mmap", "Random", "Serialization"]
uuid = "1a1011a3-84de-559e-8e89-a11a2f7dc383"

[[SnoopCompile]]
deps = ["Pkg", "Serialization", "Test"]
git-tree-sha1 = "bf278fd3d9ec1d8183dcf81291c1994561b66c93"
uuid = "aa65fe97-06da-5843-b5b1-d5d13cad87d2"
version = "0.3.1"

[[Sockets]]
uuid = "6462fe0b-24de-5631-8697-dd941f90decc"

[[SparseArrays]]
deps = ["LinearAlgebra", "Random"]
uuid = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"

[[Statistics]]
deps = ["LinearAlgebra", "SparseArrays"]
uuid = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"

[[Test]]
deps = ["Distributed", "InteractiveUtils", "Logging", "Random"]
uuid = "8dfed614-e22c-5e08-85e1-65c5234f0b40"

[[TextWrap]]
deps = ["Compat", "Test"]
git-tree-sha1 = "8355cc559e85469cd4dbe927c375f61d3750e002"
uuid = "b718987f-49a8-5099-9789-dcd902bef87d"
version = "0.3.0"

[[URIParser]]
deps = ["Test", "Unicode"]
git-tree-sha1 = "6ddf8244220dfda2f17539fa8c9de20d6c575b69"
uuid = "30578b45-9adc-5946-b283-645ec420af67"
version = "0.4.0"

[[UUIDs]]
deps = ["Random"]
uuid = "cf7118a7-6976-5b1a-9a39-7adc72f591a4"

[[Unicode]]
uuid = "4ec0a83e-493e-50e2-b9ac-8f72acf5a8f5"

[[WinRPM]]
deps = ["BinDeps", "Compat", "HTTPClient", "LibExpat", "Libdl", "Libz", "URIParser"]
git-tree-sha1 = "2a889d320f3b77d17c037f295859fe570133cfbf"
uuid = "c17dfb99-b4f7-5aad-8812-456da1ad7187"
version = "0.4.2"

Project.toml

[deps]
ArgParse = "c7e460c6-2fb9-53a9-8c5b-16f535851c63"
PackageCompiler = "9b87118b-4619-50d2-8e1e-99f35a4d4d9d"

test.jl

Base.@ccallable function func0()::Cdouble
    return sum([1.34, .7])
end

Base.@ccallable function func1()::Cdouble
    return (1.2 + .1) / 2.0
end

test.py

from pathlib import Path
import ctypes

libpath = Path(__file__).resolve().parent.joinpath("builddir", "test.so")
dll = ctypes.CDLL(libpath, ctypes.RTLD_GLOBAL)
dll.func0.restype = ctypes.c_double
dll.func1.restype = ctypes.c_double

try:
    jl_init_with_image = dll.jl_init_with_image
except AttributeError:
    jl_init_with_image = dll.jl_init_with_image__threading
jl_init_with_image.argtypes = [ctypes.c_char_p, ctypes.c_char_p]


if __name__ == "__main__":
    jl_init_with_image(None, str(libpath).encode("utf-8"))
    print("func1 =", dll.func1())
    print("func0 =", dll.func0())