000. np.empty
numpy.empty(shape, dtype=float, order='C')
Parameters:
shape : int or sequence of ints
Shape of the new array, e.g., (2, 3) or 2.
dtype : data-type, optional
The desired data-type for the array, e.g., numpy.int8. Default is numpy.float64.
order : {‘C’, ‘F’}, optional
Whether to store multidimensional data in C- or Fortran-contiguous (row- or column-wise) order in memory.
Returns:
out : ndarray
Array of ones with the given shape, dtype, and order.```
- C-API:
static struct PyMethodDef array_module_methods[] = {
...
{"empty",
(PyCFunction)array_empty,
METH_VARARGS|METH_KEYWORDS, NULL},
...
}
static PyObject *
array_empty(PyObject *NPY_UNUSED(ignored), PyObject *args, PyObject *kwds)
{
static char *kwlist[] = {"shape","dtype","order",NULL};
PyArray_Descr *typecode = NULL;
PyArray_Dims shape = {NULL, 0};
NPY_ORDER order = NPY_CORDER;
npy_bool is_f_order;
PyArrayObject *ret = NULL;
if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|O&O&", kwlist,
PyArray_IntpConverter, &shape,
PyArray_DescrConverter, &typecode,
PyArray_OrderConverter, &order)) {
goto fail;
}
switch (order) {
case NPY_CORDER:
is_f_order = NPY_FALSE;
break;
case NPY_FORTRANORDER:
is_f_order = NPY_TRUE;
break;
default:
PyErr_SetString(PyExc_ValueError,
"only 'C' or 'F' order is permitted");
goto fail;
}
ret = (PyArrayObject *)PyArray_Empty(shape.len, shape.ptr,
typecode, is_f_order);
PyDimMem_FREE(shape.ptr);
return (PyObject *)ret;
fail:
Py_XDECREF(typecode);
PyDimMem_FREE(shape.ptr);
return NULL;
}
001. np.zeros
numpy.zeros(shape, dtype=float, order='C')
Parameters:
shape : int or sequence of ints
Shape of the new array, e.g., (2, 3) or 2.
dtype : data-type, optional
The desired data-type for the array, e.g., numpy.int8. Default is numpy.float64.
order : {‘C’, ‘F’}, optional
Whether to store multidimensional data in C- or Fortran-contiguous (row- or column-wise) order in memory.
Returns:
out : ndarray
Array of zeros with the given shape, dtype, and order.
[read more](https://docs.scipy.org/doc/numpy-dev/reference/generated/numpy.zeros.html)
- **C-API**
static struct PyMethodDef array_module_methods[] = {
...
{"zeros",
(PyCFunction)array_zeros,
METH_VARARGS|METH_KEYWORDS, NULL},
...
}
static PyObject *
array_zeros(PyObject *NPY_UNUSED(ignored), PyObject *args, PyObject *kwds)
{
static char *kwlist[] = {"shape","dtype","order",NULL};
PyArray_Descr *typecode = NULL;
PyArray_Dims shape = {NULL, 0};
NPY_ORDER order = NPY_CORDER;
npy_bool is_f_order = NPY_FALSE;
PyArrayObject *ret = NULL;
if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|O&O&", kwlist,
PyArray_IntpConverter, &shape,
PyArray_DescrConverter, &typecode,
PyArray_OrderConverter, &order)) {
goto fail;
}
switch (order) {
case NPY_CORDER:
is_f_order = NPY_FALSE;
break;
case NPY_FORTRANORDER:
is_f_order = NPY_TRUE;
break;
default:
PyErr_SetString(PyExc_ValueError,
"only 'C' or 'F' order is permitted");
goto fail;
}
ret = (PyArrayObject *)PyArray_Zeros(shape.len, shape.ptr,
typecode, (int) is_f_order);
PyDimMem_FREE(shape.ptr);
return (PyObject *)ret;
fail:
Py_XDECREF(typecode);
PyDimMem_FREE(shape.ptr);
return (PyObject *)ret;
}
[read more](https://github.com/numpy/numpy/blob/master/numpy/core/src/multiarray/multiarraymodule.c#L1937-L1977)
##002. np.ones
def ones(shape, dtype=None, order='C'):
a = empty(shape, dtype, order)
multiarray.copyto(a, 1, casting='unsafe')
return a
>
Parameters
----------
shape : int or sequence of ints
Shape of the new array, e.g., ``(2, 3)`` or ``2``.
dtype : data-type, optional
The desired data-type for the array, e.g., `numpy.int8`. Default is
`numpy.float64`.
order : {'C', 'F'}, optional
Whether to store multidimensional data in C- or Fortran-contiguous
(row- or column-wise) order in memory.
Returns
-------
out : ndarray
Array of ones with the given shape, dtype, and order.
##003. np.empty_like
numpy.empty_like(a, dtype=None, order='K', subok=True)
>```
Parameters:
-----------
a : array_like
The shape and data-type of a define these same attributes of the returned array.
dtype : data-type, optional
Overrides the data type of the result.
order : {‘C’, ‘F’, ‘A’, or ‘K’}, optional
Overrides the memory layout of the result. ‘C’ means C-order, ‘F’ means F-order, ‘A’ means ‘F’ if a is Fortran contiguous, ‘C’ otherwise. ‘K’ means match the layout of a as closely as possible.
subok : bool, optional.
If True, then the newly created array will use the sub-class type of ‘a(chǎn)’, otherwise it will be a base-class array. Defaults to True.
Returns:
--------
out : ndarray
Array of uninitialized (arbitrary) data with the same shape and type as a.
- C-API
static struct PyMethodDef array_module_methods[] = {
...
{"empty_like",
(PyCFunction)array_empty_like,
METH_VARARGS|METH_KEYWORDS, NULL},
...
}
static PyObject *
array_empty_like(PyObject *NPY_UNUSED(ignored), PyObject *args, PyObject *kwds)
{
static char *kwlist[] = {"prototype","dtype","order","subok",NULL};
PyArrayObject *prototype = NULL;
PyArray_Descr *dtype = NULL;
NPY_ORDER order = NPY_KEEPORDER;
PyArrayObject *ret = NULL;
int subok = 1;
if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|O&O&i", kwlist,
&PyArray_Converter, &prototype,
&PyArray_DescrConverter2, &dtype,
&PyArray_OrderConverter, &order,
&subok)) {
goto fail;
}
/* steals the reference to dtype if it's not NULL */
ret = (PyArrayObject *)PyArray_NewLikeArray(prototype,
order, dtype, subok);
Py_DECREF(prototype);
return (PyObject *)ret;
fail:
Py_XDECREF(prototype);
Py_XDECREF(dtype);
return NULL;
}
004 np.zeros_like
def zeros_like(a, dtype=None, order='K', subok=True):
res = empty_like(a, dtype=dtype, order=order, subok=subok)
# needed instead of a 0 to get same result as zeros for for string dtypes
z = zeros(1, dtype=res.dtype)
multiarray.copyto(res, z, casting='unsafe')
return res
Parameters
----------
a : array_like
The shape and data-type of `a` define these same attributes of
the returned array.
dtype : data-type, optional
Overrides the data type of the result.
.. versionadded:: 1.6.0
order : {'C', 'F', 'A', or 'K'}, optional
Overrides the memory layout of the result. 'C' means C-order,
'F' means F-order, 'A' means 'F' if `a` is Fortran contiguous,
'C' otherwise. 'K' means match the layout of `a` as closely
as possible.
.. versionadded:: 1.6.0
subok : bool, optional.
If True, then the newly created array will use the sub-class
type of 'a', otherwise it will be a base-class array. Defaults
to True.
Returns
-------
out : ndarray
Array of zeros with the same shape and type as `a`.
005. np.ones_like
def ones_like(a, dtype=None, order='K', subok=True):
res = empty_like(a, dtype=dtype, order=order, subok=subok)
multiarray.copyto(res, 1, casting='unsafe')
return res
Parameters
----------
a : array_like
The shape and data-type of `a` define these same attributes of
the returned array.
dtype : data-type, optional
Overrides the data type of the result.
.. versionadded:: 1.6.0
order : {'C', 'F', 'A', or 'K'}, optional
Overrides the memory layout of the result. 'C' means C-order,
'F' means F-order, 'A' means 'F' if `a` is Fortran contiguous,
'C' otherwise. 'K' means match the layout of `a` as closely
as possible.
.. versionadded:: 1.6.0
subok : bool, optional.
If True, then the newly created array will use the sub-class
type of 'a', otherwise it will be a base-class array. Defaults
to True.
Returns
-------
out : ndarray
Array of ones with the same shape and type as `a`.
006. np.eye
def eye(N, M=None, k=0, dtype=float):
if M is None:
M = N
m = zeros((N, M), dtype=dtype)
if k >= M:
return m
if k >= 0:
i = k
else:
i = (-k) * M
m[:M-k].flat[i::M+1] = 1
return m
Parameters
----------
N : int
Number of rows in the output.
M : int, optional
Number of columns in the output. If None, defaults to `N`.
k : int, optional
Index of the diagonal: 0 (the default) refers to the main diagonal,
a positive value refers to an upper diagonal, and a negative value
to a lower diagonal.
dtype : data-type, optional
Data-type of the returned array.
Returns
-------
I : ndarray of shape (N,M)
An array where all elements are equal to zero, except for the `k`-th
diagonal, whose values are equal to one.
007. np.identity
def identity(n, dtype=None):
from numpy import eye
return eye(n, dtype=dtype)
Parameters
----------
n : int
Number of rows (and columns) in `n` x `n` output.
dtype : data-type, optional
Data-type of the output. Defaults to ``float``.
Returns
-------
out : ndarray
`n` x `n` array with its main diagonal set to one,
and all other elements 0.
008. np.full
def full(shape, fill_value, dtype=None, order='C'):
if dtype is None:
dtype = array(fill_value).dtype
a = empty(shape, dtype, order)
multiarray.copyto(a, fill_value, casting='unsafe')
return a
Parameters
----------
shape : int or sequence of ints
Shape of the new array, e.g., ``(2, 3)`` or ``2``.
fill_value : scalar
Fill value.
dtype : data-type, optional
The desired data-type for the array The default, `None`, means
`np.array(fill_value).dtype`.
order : {'C', 'F'}, optional
Whether to store multidimensional data in C- or Fortran-contiguous
(row- or column-wise) order in memory.
Returns
-------
out : ndarray
Array of `fill_value` with the given shape, dtype, and order.
009. np.full_like
def full_like(a, fill_value, dtype=None, order='K', subok=True):
res = empty_like(a, dtype=dtype, order=order, subok=subok)
multiarray.copyto(res, fill_value, casting='unsafe')
return res
Parameters
----------
a : array_like
The shape and data-type of `a` define these same attributes of
the returned array.
fill_value : scalar
Fill value.
dtype : data-type, optional
Overrides the data type of the result.
order : {'C', 'F', 'A', or 'K'}, optional
Overrides the memory layout of the result. 'C' means C-order,
'F' means F-order, 'A' means 'F' if `a` is Fortran contiguous,
'C' otherwise. 'K' means match the layout of `a` as closely
as possible.
subok : bool, optional.
If True, then the newly created array will use the sub-class
type of 'a', otherwise it will be a base-class array. Defaults
to True.
Returns
-------
out : ndarray
Array of `fill_value` with the same shape and type as `a`.
