将Django模型queryset转换为numpy矩阵

Question

I want to pull out a set of fields for objects in a Django queryset and convert them into a matrix with the fields as columns for some computation. I've gotten to the point of :

qs = models.Devices.objects.all()

params = qs.values('b1', 'b2', 'b3', 'b4', 'b5', 'b6', 'b7', 'b8')

which returns a list of dictionaries ordered by object.

I want to know if there's a good way to convert these into rows of a numpy matrix and also if there is a way to keep an index of where these values are held in the db?

I want to do some calculations (sometimes different ones depending on the parameter type) and then eventually use the resultant vectors to populate/overwrite an existing column in the db such that the ordering is the same.

Answer 1

You could

1. Use the values_list() method to get a list of lists. Include the id in the values.
2. Use list comprehension on the result of the query to remove the ids from the params and generate a list of ids .
3. Use the params as the parameter for numpy.matrix() .
4. Perform operations on the matrix.

5. Iterate over the ids and save the values from each row of the matrix to the corresponding object.

    import numpy as np qs = models.Devices.objects.all() params = qs.values_list('id', 'b1', 'b2', 'b3', 'b4', 'b5', 'b6', 'b7', 'b8') ids = [arr.pop(0) for arr in params] matrix = np.matrix(params) # perform operations here for index, id in enumerate(ids): row = matrix[index].flat obj = qs.get(id=id) obj.b1 = row.next() obj.b2 = row.next() obj.b3 = row.next() obj.b4 = row.next() obj.b5 = row.next() obj.b6 = row.next() obj.b7 = row.next() obj.save()