Python function call from Matlab - error occurred "Conversion to int64 from py.NoneType is not possible."

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Saswati 2024-6-13

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回答： Ayush Aniket 2024-6-14

I want to call a python function from Matlab.

I have two Python files. one file can call the other file. The content of the file named, calculation.py is as follows

def addNumbers(a, b):
print("Sum is ", a + b)
def subtractNumbers(a, b):
print("Difference is ", a - b)
def multiplyNumbers(a, b):
print("Product is ", a * b)
def divideNumbers(a, b):
print("Division is ", a / b)
def modulusNumbers(a, b):
print("Remainder is ", a % b)

The content of the another python file named call_file.py is as follows

from calculation import addNumbers, multiplyNumbers

I wrote a matlab code to call call_flie.py. The matlab code is as follows

pyenv
path_add = fileparts(which("call_file.py"))
if count(py.sys.path,path_add)==0
    insert(py.sys.path,int64(0),path_add)
end
pyOut = py.call_file.addNumbers(5, 2);
sum = int64(pyOut);
disp(sum)

I received the error "Error using int64

Conversion to int64 from py.NoneType is not possible.

Error in Test1 (line 8)

sum = int64(pyOut);

"

How can I solve the error?

Thank you.

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Answer 1

Ayush Aniket 2024-6-14

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Hi Saswati,

The error message you are getting is due to the fact that the addNumbers function in your calculation.py Python file does not return any value; it only prints the result. When you try to convert the output of py.call_file.addNumbers(5, 2) to int64 in MATLAB, it fails because the Python function effectively returns None, which cannot be directly converted to an integer in MATLAB.

To solve this issue, you need to modify your Python functions in calculation.py to return their results instead of just printing them as shown below: