Conversion to Python
Conversion Rules
The following table specifies the conversion rules used whenever converting a Julia object to a Python object.
From Julia, this occurs explicitly with Py(x) or implicitly when passing Julia objects as the argument to a Python function. To avoid this automatic conversion, the user can convert objects explicitly, such as by calling pylist or pydict.
From Python, this occurs when converting the return value of a Julia function.
| From | To |
|---|---|
Any Python object type (Py, PyList, etc.) | itself |
Nothing | None |
Bool | bool |
Integer | int |
Rational{<:Integer} | fractions.Fraction |
Float64, Float32, Float16 | float |
Complex{Float64}, Complex{Float32}, Complex{Float16} | complex |
AbstractString, AbstractChar | str |
Base.CodeUnits{UInt8} (e.g. b"example") | bytes |
Tuple, Pair | tuple |
AbstractRange{<:Integer} | range |
Dates.Date | datetime.date |
Dates.Time | datetime.time |
Dates.DateTime | datetime.datetime |
Dates.Second, Dates.Millisecond, Dates.Microsecond, Dates.Nanosecond | datetime.timedelta |
Number | juliacall.NumberValue, juliacall.ComplexValue, etc. |
AbstractArray | juliacall.ArrayValue, juliacall.VectorValue |
AbstractDict | juliacall.DictValue |
AbstractSet | juliacall.SetValue |
IO | juliacall.BufferedIOValue |
Module | juliacall.ModuleValue |
Type | juliacall.TypeValue |
| Anything else | juliacall.AnyValue |
See here for an explanation of the juliacall.*Value wrapper types.
Custom rules
You may define a new conversion rule for your new type T by overloading Py(::T).
If T is a wrapper type (such as PyList) where Py(x) simply returns the stored Python object, then also define ispy(::T) = true.
PythonCall.ispy — Functionispy(x)True if x is a Python object.
This includes Py and Python wrapper types such as PyList.
Alternatively, if you define a wrapper type (a subtype of juliacall.AnyValue) then you may instead define pyjltype(::T) to be that type.
PythonCall.pyjltype — Functionpyjltype(x)The subtype of juliacall.AnyValue which the Julia object x is wrapped as by pyjl(x).
Overload pyjltype(::T) to define a custom conversion for your type T.