Matrix fn with numpy

[survuvi]

I don't see why this error:

from PythonInterface import Python

fn create_matrix(rows : Int, cols : Int) -> object:
    # This is equivalent to Python's `import numpy as np`
    let np = Python.import_module("numpy")

    # Create matrix with numpy:
    let matrix = np.arange(1, rows*cols+1).reshape(rows, cols)

    return matrix

# Create matrix 9 rows and 5 cols:
print(create_matrix(9, 5))

error: Expression [18]:7:34: cannot call function that may raise in a context that cannot raise
let np = Python.import_module("numpy")

[lattner]

The issue here is that all calls through imported python APIs can raise an error at any time, but a 'fn' defaults not not being able to raise. Try switching create_matrix to being a def, or mark it "raises"

[DayDun]

A low priority QoL could be to explicitly mention that import_module can raise and create_matrix cannot, and suggest appropriate changes to fix the error.

[czheo]

I was also bitten by this error before: #134.
As @DayDun suggested, a better error message may help developer experience.

[iamtimdavis]

@Mogball - we should fix the error string

[Mogball]

Error message should get improved in the next release

[survuvi]

Thank you @lattner I added raises and now it works:

from PythonInterface import Python

fn create_matrix(rows : Int, cols : Int) raises -> PythonObject:
    # This is equivalent to Python's `import numpy as np`
    let np = Python.import_module("numpy")

    # Create matrix with numpy:
    let matrix = np.arange(1, rows*cols+1).reshape(rows, cols)

    return matrix

# Create matrix 9 rows and 5 cols:
print(create_matrix(9, 5))

[gautam-e]

I had a similar issue on a fn that I wanted to vectorise.

Am I right to say that vectorize-ing such a fn is not possible because vectorize requires a func: fn[Int](Int) capturing -> None and it will not work with a fn[Int](Int) raises capturing -> None?

[survuvi]

I solved all my problems abandoning mojo for c++, mojo is undoubtedly an interesting project, even if it's a soup of multiple languages, but it's impossible to follow at the moment, it's too early stage and too confusing, even input doesn't work..