What are practical examples of using composite types in numpy?-CodePudding

The numpy documentation describes the option to create custom composite types.

How should one use them?

I can imagine a practical example being a composite time format that would could be used to unify python, hdf5 and numpy as for example:

custom_time = np.dtype( [ ('h', np.int8) , ('m', np.int8), ('s', np.float)] )

t = custom_time(23,59,59.99999)

(the line above doesn't work - I get TypeError: 'numpy.dtype[void]' object is not callable)

Perhaps you have used composite types and have an idea?

CodePudding user response：

Custom types are meant to be used in Numpy arrays and not as stand-alone types. Here is an example:

# Declare the type
custom_time = np.dtype( [ ('h', np.int8) , ('m', np.int8), ('s', np.float64)] )

# Create an array with 2 items of custom_time
arr = np.array([(4, 8, 15.16), (23, 42, 0.815)], dtype=custom_time)

# Access the fields
print(arr['h'])   # [4 23]
print(arr['s'])   # [15.16 0.815]