Python error only size-1 arrays can be converted to Python scalars

I’m writing a tKinter GUI and I’ve come accross a problem. Given the the main code is way to large, I’ve made a dummy example to replicate my problem.

class test():
    def __init__(self,time,a):
        
        self.time = time
        self.a = a
    
    def something(self):
        
        self.b = float(self.time) * self.a
        
        return {'bVar':self.b}

time = np.linspace(0,100,10)
testObj = test(time,2.2)
print(testObj.something().get('bVar'))

The error is:

----> 9         self.b = float(self.time) * self.a
     10 
     11         return {'bVar':self.b}

TypeError: only size-1 arrays can be converted to Python scalars

If I remove the float conversion of time, then it works. But in my main GUI I need to keep float(self.time). self.a in my GUI is a tKinter entry that has to be also of type float(entry[1].get())

Any thoughts on how I can remedy this?

Answer

The error “only length-1 arrays can be converted to Python scalars” is raised when the function expects a single value but you pass an array instead.

Problem is that you are passing an array self.time to the float that expects a single value instead of an array.

You got time using np.linspace(0, 100, 10) which returns an array of evenly spaced numbers over a specified interval.

https://numpy.org/doc/stable/reference/generated/numpy.linspace.html

Updating my answer, assuming you want to multiply each value in the list with a single value.

class Test():
    def __init__(self,time,a):
        self.time = time
        self.a = a
    
    def something(self):
        self.b = np.array(self.time, dtype=float) * self.a
        return {'bVar':self.b}

time = np.linspace(0,100,10)
testObj = Test(time,2.2)
print(testObj.something().get('bVar'))

You can set dtype=float in numpy array to set the data type of the array to float. And then you can use * to multiply a single value with each value in the array.