# Error when calling ScikitLearn from a function in a Package

**URL:** <https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131>\
**Category:** General Usage\
**Tags:** package\
**Created:** [September 6, 2020, 7:00am UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131 "2020-09-06T07:00:52Z")\
**Posts on this page:** 8\
**Page:** 1

<div class="post-metadata">

**Author:** ![e3c6](https://avatars.discourse-cdn.com/v4/letter/e/e79b87/32.png) [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Post date:** [September 6, 2020, 7:00am UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/1 "2020-09-06T07:00:52Z")

</div>

I have a function inside a package that I am writing, that looks like this:

```julia
using ScikitLearn

function logistic_skl(points::AbstractMatrix{<:Real}, labels::AbstractVector{Bool})
    @sk_import linear_model: LogisticRegression
    log_reg = fit!(LogisticRegression(penalty="l2"), points', labels)
    w = vec(log_reg.coef_)
    b = only(log_reg.intercept_)
    return w, b
end

```

But the package containing this function (say `MyPkg.jl`) now fails to pre-compile, with the following error (pointing to the function above):

```julia
ERROR: LoadError: LoadError: syntax: unsupported `const` declaration on local variable around /home/cossio/.julia/packages/ScikitLearn/Kn82b/src/Skcore.jl:187
Stacktrace:
 [1] top-level scope at /home/cossio/jl/MyPkg.jl/src/logistic_sklearn.jl:5
 [2] include(::Function, ::Module, ::String) at ./Base.jl:380
 [3] include at ./Base.jl:368 [inlined]
 [4] include(::String) at /home/cossio/jl/MyPkg.jl/src/MyPkg.jl:1
 [5] top-level scope at /home/cossio/jl/MyPkg.jl/src/MyPkg.jl:26
 [6] include(::Function, ::Module, ::String) at ./Base.jl:380
 [7] include(::Module, ::String) at ./Base.jl:368
 [8] top-level scope at none:2
 [9] eval at ./boot.jl:331 [inlined]
 [10] eval(::Expr) at ./client.jl:467
 [11] top-level scope at ./none:3
in expression starting at /home/cossio/jl/MyPkg.jl/src/logistic_sklearn.jl:5
in expression starting at /home/cossio/jl/MyPkg.jl/src/MyPkg.jl:26

```

How can I fix this?

---

<div class="post-metadata">

**Author:** ![Vasily\_Pisarev](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vasily_pisarev/32/7929_2.png) [@Vasily\_Pisarev](https://discourse.julialang.org/u/Vasily_Pisarev)\
**Post date:** [September 6, 2020, 7:17am UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/2 "2020-09-06T07:17:53Z")

</div>

The `const` comes from the expansion of `@sk_import`. So, put that line in the toplevel, not inside the function.

---

<div class="post-metadata">

**Author:** ![e3c6](https://avatars.discourse-cdn.com/v4/letter/e/e79b87/32.png) [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Post date:** [September 6, 2020, 12:49pm UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/3 "2020-09-06T12:49:07Z")

</div>

If I put it at the top level,

```julia
@sk_import linear_model: LogisticRegression
function logistic_skl(points::AbstractMatrix{<:Real}, labels::AbstractVector{Bool})
    log_reg = fit!(LogisticRegression(penalty="l2"), points', labels)
    w = vec(log_reg.coef_)
    b = only(log_reg.intercept_)
    return w, b
end

```

I get a segmentation fault:

```julia

signal (11): Segmentation fault
in expression starting at /home/cossio/jl/MyPkg.jl/test/logistic.jl:22
PyObject_Call at /home/cossio/.julia/conda/3/lib/libpython3.8.so.1.0 (unknown line)
Allocations: 383287667 (Pool: 382734699; Big: 552968); GC: 213
ERROR: Package MyPkg errored during testing (received signal: 11)

```

The referred line 22 in the test file simply calls `logistic_skl` with some data.

---

<div class="post-metadata">

**Author:** ![Vasily\_Pisarev](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vasily_pisarev/32/7929_2.png) [@Vasily\_Pisarev](https://discourse.julialang.org/u/Vasily_Pisarev)\
**Post date:** [September 6, 2020, 8:41pm UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/4 "2020-09-06T20:41:01Z")

</div>

Likely some incompatibility in data layouts.  
Which data types do you pass for `points` and `labels`?

---

<div class="post-metadata">

**Author:** ![e3c6](https://avatars.discourse-cdn.com/v4/letter/e/e79b87/32.png) [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Post date:** [September 6, 2020, 9:23pm UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/5 "2020-09-06T21:23:55Z")

</div>

Here is the data I am using. Note that if I run these lines of code from a console, it works fine. The problem comes when this is inside a package.

```julia
@sk_import linear_model: LogisticRegression
function logistic_skl(points::AbstractMatrix{<:Real}, labels::AbstractVector{Bool})
    log_reg = fit!(LogisticRegression(penalty="l2"), points', labels)
    w = vec(log_reg.coef_)
    b = only(log_reg.intercept_)
    return w, b
end

# Generate data.
n = 2 # dimensionality of data
N = 10 # number of positive examples
M = 10 # number of negative examples
points = randn(n, N + M) .+ [fill(5, n, N) fill(-5, n, M)]
labels = [trues(N); falses(M)]

# logistic regression
w, b = logistic_skl(points, labels)

```

---

<div class="post-metadata">

**Author:** ![e3c6](https://avatars.discourse-cdn.com/v4/letter/e/e79b87/32.png) [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Post date:** [September 7, 2020, 8:41am UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/6 "2020-09-07T08:41:52Z")

</div>

This looks related,

> [@Imported ScikitLearn PyObj becomes NULL in a module](https://discourse.julialang.org/t/imported-scikitlearn-pyobj-becomes-null-in-a-module/30942/2):
>
> Yeah that’s tricky, you need to place the import in the init function, see how I did it here [https://github.com/baggepinnen/HDBSCAN.jl/blob/master/src/HDBSCAN.jl](https://github.com/baggepinnen/HDBSCAN.jl/blob/master/src/HDBSCAN.jl)

I tried doing this, but is not working:

```julia
    using ScikitLearn, PyCall
    const LogisticRegression = PyNULL()
    function __init__ ()
        @eval global LogisticRegression = pyimport("linear_model")
    end

```

Gives this error:

```julia
  Got exception outside of a @test
  LoadError: InitError: PyError (PyImport_ImportModule
  
  The Python package linear_model could not be found by pyimport. Usually this means
  that you did not install linear_model in the Python version being used by PyCall.

```

---

<div class="post-metadata">

**Author:** ![Vasily\_Pisarev](https://sea2.discourse-cdn.com/julialang/user_avatar/discourse.julialang.org/vasily_pisarev/32/7929_2.png) [@Vasily\_Pisarev](https://discourse.julialang.org/u/Vasily_Pisarev)\
**Post date:** [September 7, 2020, 10:13am UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/7 "2020-09-07T10:13:32Z")

</div>

What if you do `@eval @sk_import linear_model: LogisticRegression` in the ` __init__ ` function?

---

<div class="post-metadata">

**Author:** ![e3c6](https://avatars.discourse-cdn.com/v4/letter/e/e79b87/32.png) [@e3c6](https://discourse.julialang.org/u/e3c6)\
**Post date:** [September 8, 2020, 7:03am UTC](https://discourse.julialang.org/t/error-when-calling-scikitlearn-from-a-function-in-a-package/46131/8 "2020-09-08T07:03:13Z")

</div>

Thanks! This works,

```julia
using ScikitLearn, PyCall

const LogisticRegression = PyNULL()

function __init__ ()
    @eval @sk_import linear_model: LogisticRegression
end

function logistic_skl(points::AbstractMatrix{<:Real}, labels::AbstractVector{Bool})
    log_reg = fit!(LogisticRegression(penalty="l2"), points', labels)
    w = vec(log_reg.coef_)
    b = only(log_reg.intercept_)
    return w, b
end

```

However, I do get a warning from modifying the `const`:

> WARNING: redefinition of constant LogisticRegression. This may fail, cause incorrect answers, or produce other errors.

So I suppose there should still be a better way.