Integration with Python
Export to Python
When the Erg script is compiled, a .pyc file is generated, which can simply be imported as a Python module. However, variables set to private on the Erg side cannot be accessed from Python.
# foo.er .public = "this is a public variable" private = "this is a private variable"
erg --compile foo.er
import foo print(foo.public) print(foo.private) # AttributeError:
import from Python
By default, all objects imported from Python are of type
Object. Since no comparison is possible with this type, it is necessary to narrow down the type.
Type specification in the standard library
All APIs in the Python standard library are type-specified by the Erg development team.
time = pyimport "time" time.sleep! 1
Type specification for user scripts
Type hints on the Python side are ignored. Create a
foo.d.er file that types the Python
# foo.py X = ... def bar(x): ... def baz(): ... class C: ... ...
# foo.d.er .X: Int .bar!: Int => Int .foo! = baz!: () => Int # aliasing .C!: Class
No syntax other than declarations and definitions (aliasing) are allowed in
Note that all Python functions can only be registered as procedures, and all classes as variable classes.
foo = pyimport "foo" assert foo.bar!(1) in Int
This ensures type safety by performing type checking at runtime. The checking mechanism generally works as follows.
decl_proc proc!: Proc, T = x => assert x in T.Input y = proc!(x) assert y in T.Output y
This is a runtime overhead, so a project to statically type analyze Python scripts with Erg's type system is underway.