dtype，type，astype()的差别

标题type定义的是数据结构类型 list,dict,numpy等等

>>> k = [1, 2]
>>> type(k)
<class 'list'>

>>> import numpy as np
>>> p = np.array(k)
>>> type(p)
<class 'numpy.ndarray'>

dtype定义的是数据的类型，比如int, float等

>>> import numpy as np
>>> p = np.array(k)
>>> p.dtype
dtype('int32')

astype():

>>> import numpy as np
>>> p = np.array(k)
>>> p
array([1, 2])
>>> p.astype(float)
array([1., 2.])