numpy.asarray#

numpy.asarray(a, dtype=None, order=None, *, device=None, copy=None, like=None)#

Convert the input to an array.

Parameters:

aarray_like: Input data, in any form that can be converted to an array. This includes lists, lists of tuples, tuples, tuples of tuples, tuples of lists and ndarrays.
dtypedata-type, optional: By default, the data-type is inferred from the input data.
order{『C』, 『F』, 『A』, 『K』}, optional: The memory layout of the output. 『C』 gives a row-major layout (C-style), 『F』 gives a column-major layout (Fortran-style). 『C』 and 『F』 will copy if needed to ensure the output format. 『A』 (any) is equivalent to 『F』 if input a is non-contiguous or Fortran-contiguous, otherwise, it is equivalent to 『C』. Unlike 『C』 or 『F』, 『A』 does not ensure that the result is contiguous. 『K』 (keep) is the default and preserves the input order for the output.
devicestr, optional: The device on which to place the created array. Default: None. For Array-API interoperability only, so must be "cpu" if passed.

在 2.0.0 版新加入.
copybool, optional: If True, then the object is copied. If None then the object is copied only if needed, i.e. if __array__ returns a copy, if obj is a nested sequence, or if a copy is needed to satisfy any of the other requirements (dtype, order, etc.). For False it raises a ValueError if a copy cannot be avoided. Default: None.

在 2.0.0 版新加入.
likearray_like, optional: Reference object to allow the creation of arrays which are not NumPy arrays. If an array-like passed in as like supports the __array_function__ protocol, the result will be defined by it. In this case, it ensures the creation of an array object compatible with that passed in via this argument.

在 1.20.0 版新加入.

Returns:

outndarray: Array interpretation of a. No copy is performed if the input is already an ndarray with matching dtype and order. If a is a subclass of ndarray, a base class ndarray is returned.

也參考

asanyarray: Similar function which passes through subclasses.
ascontiguousarray: Convert input to a contiguous array.
asfortranarray: Convert input to an ndarray with column-major memory order.
asarray_chkfinite: Similar function which checks input for NaNs and Infs.
fromiter: Create an array from an iterator.
fromfunction: Construct an array by executing a function on grid positions.

Examples

Convert a list into an array:

>>> a = [1, 2]
>>> import numpy as np
>>> np.asarray(a)
array([1, 2])

Existing arrays are not copied:

>>> a = np.array([1, 2])
>>> np.asarray(a) is a
True

If dtype is set, array is copied only if dtype does not match:

>>> a = np.array([1, 2], dtype=np.float32)
>>> np.shares_memory(np.asarray(a, dtype=np.float32), a)
True
>>> np.shares_memory(np.asarray(a, dtype=np.float64), a)
False

Contrary to asanyarray, ndarray subclasses are not passed through:

>>> issubclass(np.recarray, np.ndarray)
True
>>> a = np.array([(1., 2), (3., 4)], dtype='f4,i4').view(np.recarray)
>>> np.asarray(a) is a
False
>>> np.asanyarray(a) is a
True