1，打印當前Numpy版本

import numpy as np
print (np.__version__)
"""
1.22.3
"""

2，構造一個全零的矩陣，并打印其占用的內存大小

yy = np.zeros((3,3))
yy
"""
array([[0., 0., 0.],[0., 0., 0.],[0., 0., 0.]])
"""

print('%d bytes'%(yy.size * yy.itemsize))
"""
72 bytes
"""

3，打印一個函數的幫助文檔，比如numpy.add

print(help(np.add))
"""
Help on ufunc object:add = class ufunc(builtins.object)|  Functions that operate element by element on whole arrays.|  |  To see the documentation for a specific ufunc, use `info`.  For|  example, ``np.info(np.sin)``.  Because ufuncs are written in C|  (for speed) and linked into Python with NumPy's ufunc facility,|  Python's help() function finds this page whenever help() is called|  on a ufunc.|  |  A detailed explanation of ufuncs can be found in the docs for :ref:`ufuncs`.|  |  **Calling ufuncs:** ``op(*x[, out], where=True, **kwargs)``|  |  Apply `op` to the arguments `*x` elementwise, broadcasting the arguments.|  |  The broadcasting rules are:|  |  * Dimensions of length 1 may be prepended to either array.|  * Arrays may be repeated along dimensions of length 1.|  |  Parameters|  ----------|  *x : array_like|      Input arrays.|  out : ndarray, None, or tuple of ndarray and None, optional|      Alternate array object(s) in which to put the result; if provided, it|      must have a shape that the inputs broadcast to. A tuple of arrays|      (possible only as a keyword argument) must have length equal to the|      number of outputs; use None for uninitialized outputs to be|      allocated by the ufunc.|  where : array_like, optional|      This condition is broadcast over the input. At locations where the|      condition is True, the `out` array will be set to the ufunc result.|      Elsewhere, the `out` array will retain its original value.|      Note that if an uninitialized `out` array is created via the default|      ``out=None``, locations within it where the condition is False will|      remain uninitialized.|  **kwargs|      For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.|  |  Returns|  -------|  r : ndarray or tuple of ndarray|      `r` will have the shape that the arrays in `x` broadcast to; if `out` is|      provided, it will be returned. If not, `r` will be allocated and|      may contain uninitialized values. If the function has more than one|      output, then the result will be a tuple of arrays.|  |  Methods defined here:|  |  __call__(self, /, *args, **kwargs)|      Call self as a function.|  |  __repr__(self, /)|      Return repr(self).|  |  __str__(self, /)|      Return str(self).|  |  accumulate(...)|      accumulate(array, axis=0, dtype=None, out=None)|      |      Accumulate the result of applying the operator to all elements.|      |      For a one-dimensional array, accumulate produces results equivalent to::|      |        r = np.empty(len(A))|        t = op.identity        # op = the ufunc being applied to A's  elements|        for i in range(len(A)):|            t = op(t, A[i])|            r[i] = t|        return r|      |      For example, add.accumulate() is equivalent to np.cumsum().|      |      For a multi-dimensional array, accumulate is applied along only one|      axis (axis zero by default; see Examples below) so repeated use is|      necessary if one wants to accumulate over multiple axes.|      |      Parameters|      ----------|      array : array_like|          The array to act on.|      axis : int, optional|          The axis along which to apply the accumulation; default is zero.|      dtype : data-type code, optional|          The data-type used to represent the intermediate results. Defaults|          to the data-type of the output array if such is provided, or the|          the data-type of the input array if no output array is provided.|      out : ndarray, None, or tuple of ndarray and None, optional|          A location into which the result is stored. If not provided or None,|          a freshly-allocated array is returned. For consistency with|          ``ufunc.__call__``, if given as a keyword, this may be wrapped in a|          1-element tuple.|      |          .. versionchanged:: 1.13.0|             Tuples are allowed for keyword argument.|      |      Returns|      -------|      r : ndarray|          The accumulated values. If `out` was supplied, `r` is a reference to|          `out`.|      |      Examples|      --------|      1-D array examples:|      |      >>> np.add.accumulate([2, 3, 5])|      array([ 2,  5, 10])|      >>> np.multiply.accumulate([2, 3, 5])|      array([ 2,  6, 30])|      |      2-D array examples:|      |      >>> I = np.eye(2)|      >>> I|      array([[1.,  0.],|             [0.,  1.]])|      |      Accumulate along axis 0 (rows), down columns:|      |      >>> np.add.accumulate(I, 0)|      array([[1.,  0.],|             [1.,  1.]])|      >>> np.add.accumulate(I) # no axis specified = axis zero|      array([[1.,  0.],|             [1.,  1.]])|      |      Accumulate along axis 1 (columns), through rows:|      |      >>> np.add.accumulate(I, 1)|      array([[1.,  1.],|             [0.,  1.]])|  |  at(...)|      at(a, indices, b=None, /)|      |      Performs unbuffered in place operation on operand 'a' for elements|      specified by 'indices'. For addition ufunc, this method is equivalent to|      ``a[indices] += b``, except that results are accumulated for elements that|      are indexed more than once. For example, ``a[[0,0]] += 1`` will only|      increment the first element once because of buffering, whereas|      ``add.at(a, [0,0], 1)`` will increment the first element twice.|      |      .. versionadded:: 1.8.0|      |      Parameters|      ----------|      a : array_like|          The array to perform in place operation on.|      indices : array_like or tuple|          Array like index object or slice object for indexing into first|          operand. If first operand has multiple dimensions, indices can be a|          tuple of array like index objects or slice objects.|      b : array_like|          Second operand for ufuncs requiring two operands. Operand must be|          broadcastable over first operand after indexing or slicing.|      |      Examples|      --------|      Set items 0 and 1 to their negative values:|      |      >>> a = np.array([1, 2, 3, 4])|      >>> np.negative.at(a, [0, 1])|      >>> a|      array([-1, -2,  3,  4])|      |      Increment items 0 and 1, and increment item 2 twice:|      |      >>> a = np.array([1, 2, 3, 4])|      >>> np.add.at(a, [0, 1, 2, 2], 1)|      >>> a|      array([2, 3, 5, 4])|      |      Add items 0 and 1 in first array to second array,|      and store results in first array:|      |      >>> a = np.array([1, 2, 3, 4])|      >>> b = np.array([1, 2])|      >>> np.add.at(a, [0, 1], b)|      >>> a|      array([2, 4, 3, 4])|  |  outer(...)|      outer(A, B, /, **kwargs)|      |      Apply the ufunc `op` to all pairs (a, b) with a in `A` and b in `B`.|      |      Let ``M = A.ndim``, ``N = B.ndim``. Then the result, `C`, of|      ``op.outer(A, B)`` is an array of dimension M + N such that:|      |      .. math:: C[i_0, ..., i_{M-1}, j_0, ..., j_{N-1}] =|         op(A[i_0, ..., i_{M-1}], B[j_0, ..., j_{N-1}])|      |      For `A` and `B` one-dimensional, this is equivalent to::|      |        r = empty(len(A),len(B))|        for i in range(len(A)):|            for j in range(len(B)):|                r[i,j] = op(A[i], B[j])  # op = ufunc in question|      |      Parameters|      ----------|      A : array_like|          First array|      B : array_like|          Second array|      kwargs : any|          Arguments to pass on to the ufunc. Typically `dtype` or `out`.|          See `ufunc` for a comprehensive overview of all available arguments.|      |      Returns|      -------|      r : ndarray|          Output array|      |      See Also|      --------|      numpy.outer : A less powerful version of ``np.multiply.outer``|                    that `ravel`\ s all inputs to 1D. This exists|                    primarily for compatibility with old code.|      |      tensordot : ``np.tensordot(a, b, axes=((), ()))`` and|                  ``np.multiply.outer(a, b)`` behave same for all|                  dimensions of a and b.|      |      Examples|      --------|      >>> np.multiply.outer([1, 2, 3], [4, 5, 6])|      array([[ 4,  5,  6],|             [ 8, 10, 12],|             [12, 15, 18]])|      |      A multi-dimensional example:|      |      >>> A = np.array([[1, 2, 3], [4, 5, 6]])|      >>> A.shape|      (2, 3)|      >>> B = np.array([[1, 2, 3, 4]])|      >>> B.shape|      (1, 4)|      >>> C = np.multiply.outer(A, B)|      >>> C.shape; C|      (2, 3, 1, 4)|      array([[[[ 1,  2,  3,  4]],|              [[ 2,  4,  6,  8]],|              [[ 3,  6,  9, 12]]],|             [[[ 4,  8, 12, 16]],|              [[ 5, 10, 15, 20]],|              [[ 6, 12, 18, 24]]]])|  |  reduce(...)|      reduce(array, axis=0, dtype=None, out=None, keepdims=False, initial=<no value>, where=True)|      |      Reduces `array`'s dimension by one, by applying ufunc along one axis.|      |      Let :math:`array.shape = (N_0, ..., N_i, ..., N_{M-1})`.  Then|      :math:`ufunc.reduce(array, axis=i)[k_0, ..,k_{i-1}, k_{i+1}, .., k_{M-1}]` =|      the result of iterating `j` over :math:`range(N_i)`, cumulatively applying|      ufunc to each :math:`array[k_0, ..,k_{i-1}, j, k_{i+1}, .., k_{M-1}]`.|      For a one-dimensional array, reduce produces results equivalent to:|      ::|      |       r = op.identity # op = ufunc|       for i in range(len(A)):|         r = op(r, A[i])|       return r|      |      For example, add.reduce() is equivalent to sum().|      |      Parameters|      ----------|      array : array_like|          The array to act on.|      axis : None or int or tuple of ints, optional|          Axis or axes along which a reduction is performed.|          The default (`axis` = 0) is perform a reduction over the first|          dimension of the input array. `axis` may be negative, in|          which case it counts from the last to the first axis.|      |          .. versionadded:: 1.7.0|      |          If this is None, a reduction is performed over all the axes.|          If this is a tuple of ints, a reduction is performed on multiple|          axes, instead of a single axis or all the axes as before.|      |          For operations which are either not commutative or not associative,|          doing a reduction over multiple axes is not well-defined. The|          ufuncs do not currently raise an exception in this case, but will|          likely do so in the future.|      dtype : data-type code, optional|          The type used to represent the intermediate results. Defaults|          to the data-type of the output array if this is provided, or|          the data-type of the input array if no output array is provided.|      out : ndarray, None, or tuple of ndarray and None, optional|          A location into which the result is stored. If not provided or None,|          a freshly-allocated array is returned. For consistency with|          ``ufunc.__call__``, if given as a keyword, this may be wrapped in a|          1-element tuple.|      |          .. versionchanged:: 1.13.0|             Tuples are allowed for keyword argument.|      keepdims : bool, optional|          If this is set to True, the axes which are reduced are left|          in the result as dimensions with size one. With this option,|          the result will broadcast correctly against the original `array`.|      |          .. versionadded:: 1.7.0|      initial : scalar, optional|          The value with which to start the reduction.|          If the ufunc has no identity or the dtype is object, this defaults|          to None - otherwise it defaults to ufunc.identity.|          If ``None`` is given, the first element of the reduction is used,|          and an error is thrown if the reduction is empty.|      |          .. versionadded:: 1.15.0|      |      where : array_like of bool, optional|          A boolean array which is broadcasted to match the dimensions|          of `array`, and selects elements to include in the reduction. Note|          that for ufuncs like ``minimum`` that do not have an identity|          defined, one has to pass in also ``initial``.|      |          .. versionadded:: 1.17.0|      |      Returns|      -------|      r : ndarray|          The reduced array. If `out` was supplied, `r` is a reference to it.|      |      Examples|      --------|      >>> np.multiply.reduce([2,3,5])|      30|      |      A multi-dimensional array example:|      |      >>> X = np.arange(8).reshape((2,2,2))|      >>> X|      array([[[0, 1],|              [2, 3]],|             [[4, 5],|              [6, 7]]])|      >>> np.add.reduce(X, 0)|      array([[ 4,  6],|             [ 8, 10]])|      >>> np.add.reduce(X) # confirm: default axis value is 0|      array([[ 4,  6],|             [ 8, 10]])|      >>> np.add.reduce(X, 1)|      array([[ 2,  4],|             [10, 12]])|      >>> np.add.reduce(X, 2)|      array([[ 1,  5],|             [ 9, 13]])|      |      You can use the ``initial`` keyword argument to initialize the reduction|      with a different value, and ``where`` to select specific elements to include:|      |      >>> np.add.reduce([10], initial=5)|      15|      >>> np.add.reduce(np.ones((2, 2, 2)), axis=(0, 2), initial=10)|      array([14., 14.])|      >>> a = np.array([10., np.nan, 10])|      >>> np.add.reduce(a, where=~np.isnan(a))|      20.0|      |      Allows reductions of empty arrays where they would normally fail, i.e.|      for ufuncs without an identity.|      |      >>> np.minimum.reduce([], initial=np.inf)|      inf|      >>> np.minimum.reduce([[1., 2.], [3., 4.]], initial=10., where=[True, False])|      array([ 1., 10.])|      >>> np.minimum.reduce([])|      Traceback (most recent call last):|          ...|      ValueError: zero-size array to reduction operation minimum which has no identity|  |  reduceat(...)|      reduceat(array, indices, axis=0, dtype=None, out=None)|      |      Performs a (local) reduce with specified slices over a single axis.|      |      For i in ``range(len(indices))``, `reduceat` computes|      ``ufunc.reduce(array[indices[i]:indices[i+1]])``, which becomes the i-th|      generalized "row" parallel to `axis` in the final result (i.e., in a|      2-D array, for example, if `axis = 0`, it becomes the i-th row, but if|      `axis = 1`, it becomes the i-th column).  There are three exceptions to this:|      |      * when ``i = len(indices) - 1`` (so for the last index),|        ``indices[i+1] = array.shape[axis]``.|      * if ``indices[i] >= indices[i + 1]``, the i-th generalized "row" is|        simply ``array[indices[i]]``.|      * if ``indices[i] >= len(array)`` or ``indices[i] < 0``, an error is raised.|      |      The shape of the output depends on the size of `indices`, and may be|      larger than `array` (this happens if ``len(indices) > array.shape[axis]``).|      |      Parameters|      ----------|      array : array_like|          The array to act on.|      indices : array_like|          Paired indices, comma separated (not colon), specifying slices to|          reduce.|      axis : int, optional|          The axis along which to apply the reduceat.|      dtype : data-type code, optional|          The type used to represent the intermediate results. Defaults|          to the data type of the output array if this is provided, or|          the data type of the input array if no output array is provided.|      out : ndarray, None, or tuple of ndarray and None, optional|          A location into which the result is stored. If not provided or None,|          a freshly-allocated array is returned. For consistency with|          ``ufunc.__call__``, if given as a keyword, this may be wrapped in a|          1-element tuple.|      |          .. versionchanged:: 1.13.0|             Tuples are allowed for keyword argument.|      |      Returns|      -------|      r : ndarray|          The reduced values. If `out` was supplied, `r` is a reference to|          `out`.|      |      Notes|      -----|      A descriptive example:|      |      If `array` is 1-D, the function `ufunc.accumulate(array)` is the same as|      ``ufunc.reduceat(array, indices)[::2]`` where `indices` is|      ``range(len(array) - 1)`` with a zero placed|      in every other element:|      ``indices = zeros(2 * len(array) - 1)``,|      ``indices[1::2] = range(1, len(array))``.|      |      Don't be fooled by this attribute's name: `reduceat(array)` is not|      necessarily smaller than `array`.|      |      Examples|      --------|      To take the running sum of four successive values:|      |      >>> np.add.reduceat(np.arange(8),[0,4, 1,5, 2,6, 3,7])[::2]|      array([ 6, 10, 14, 18])|      |      A 2-D example:|      |      >>> x = np.linspace(0, 15, 16).reshape(4,4)|      >>> x|      array([[ 0.,   1.,   2.,   3.],|             [ 4.,   5.,   6.,   7.],|             [ 8.,   9.,  10.,  11.],|             [12.,  13.,  14.,  15.]])|      |      ::|      |       # reduce such that the result has the following five rows:|       # [row1 + row2 + row3]|       # [row4]|       # [row2]|       # [row3]|       # [row1 + row2 + row3 + row4]|      |      >>> np.add.reduceat(x, [0, 3, 1, 2, 0])|      array([[12.,  15.,  18.,  21.],|             [12.,  13.,  14.,  15.],|             [ 4.,   5.,   6.,   7.],|             [ 8.,   9.,  10.,  11.],|             [24.,  28.,  32.,  36.]])|      |      ::|      |       # reduce such that result has the following two columns:|       # [col1 * col2 * col3, col4]|      |      >>> np.multiply.reduceat(x, [0, 3], 1)|      array([[   0.,     3.],|             [ 120.,     7.],|             [ 720.,    11.],|             [2184.,    15.]])|  |  ----------------------------------------------------------------------|  Data descriptors defined here:|  |  identity|      The identity value.|      |      Data attribute containing the identity element for the ufunc, if it has one.|      If it does not, the attribute value is None.|      |      Examples|      --------|      >>> np.add.identity|      0|      >>> np.multiply.identity|      1|      >>> np.power.identity|      1|      >>> print(np.exp.identity)|      None|  |  nargs|      The number of arguments.|      |      Data attribute containing the number of arguments the ufunc takes, including|      optional ones.|      |      Notes|      -----|      Typically this value will be one more than what you might expect because all|      ufuncs take  the optional "out" argument.|      |      Examples|      --------|      >>> np.add.nargs|      3|      >>> np.multiply.nargs|      3|      >>> np.power.nargs|      3|      >>> np.exp.nargs|      2|  |  nin|      The number of inputs.|      |      Data attribute containing the number of arguments the ufunc treats as input.|      |      Examples|      --------|      >>> np.add.nin|      2|      >>> np.multiply.nin|      2|      >>> np.power.nin|      2|      >>> np.exp.nin|      1|  |  nout|      The number of outputs.|      |      Data attribute containing the number of arguments the ufunc treats as output.|      |      Notes|      -----|      Since all ufuncs can take output arguments, this will always be (at least) 1.|      |      Examples|      --------|      >>> np.add.nout|      1|      >>> np.multiply.nout|      1|      >>> np.power.nout|      1|      >>> np.exp.nout|      1|  |  ntypes|      The number of types.|      |      The number of numerical NumPy types - of which there are 18 total - on which|      the ufunc can operate.|      |      See Also|      --------|      numpy.ufunc.types|      |      Examples|      --------|      >>> np.add.ntypes|      18|      >>> np.multiply.ntypes|      18|      >>> np.power.ntypes|      17|      >>> np.exp.ntypes|      7|      >>> np.remainder.ntypes|      14|  |  signature|      Definition of the core elements a generalized ufunc operates on.|      |      The signature determines how the dimensions of each input/output array|      are split into core and loop dimensions:|      |      1. Each dimension in the signature is matched to a dimension of the|         corresponding passed-in array, starting from the end of the shape tuple.|      2. Core dimensions assigned to the same label in the signature must have|         exactly matching sizes, no broadcasting is performed.|      3. The core dimensions are removed from all inputs and the remaining|         dimensions are broadcast together, defining the loop dimensions.|      |      Notes|      -----|      Generalized ufuncs are used internally in many linalg functions, and in|      the testing suite; the examples below are taken from these.|      For ufuncs that operate on scalars, the signature is None, which is|      equivalent to '()' for every argument.|      |      Examples|      --------|      >>> np.core.umath_tests.matrix_multiply.signature|      '(m,n),(n,p)->(m,p)'|      >>> np.linalg._umath_linalg.det.signature|      '(m,m)->()'|      >>> np.add.signature is None|      True  # equivalent to '(),()->()'|  |  types|      Returns a list with types grouped input->output.|      |      Data attribute listing the data-type "Domain-Range" groupings the ufunc can|      deliver. The data-types are given using the character codes.|      |      See Also|      --------|      numpy.ufunc.ntypes|      |      Examples|      --------|      >>> np.add.types|      ['??->?', 'bb->b', 'BB->B', 'hh->h', 'HH->H', 'ii->i', 'II->I', 'll->l',|      'LL->L', 'qq->q', 'QQ->Q', 'ff->f', 'dd->d', 'gg->g', 'FF->F', 'DD->D',|      'GG->G', 'OO->O']|      |      >>> np.multiply.types|      ['??->?', 'bb->b', 'BB->B', 'hh->h', 'HH->H', 'ii->i', 'II->I', 'll->l',|      'LL->L', 'qq->q', 'QQ->Q', 'ff->f', 'dd->d', 'gg->g', 'FF->F', 'DD->D',|      'GG->G', 'OO->O']|      |      >>> np.power.types|      ['bb->b', 'BB->B', 'hh->h', 'HH->H', 'ii->i', 'II->I', 'll->l', 'LL->L',|      'qq->q', 'QQ->Q', 'ff->f', 'dd->d', 'gg->g', 'FF->F', 'DD->D', 'GG->G',|      'OO->O']|      |      >>> np.exp.types|      ['f->f', 'd->d', 'g->g', 'F->F', 'D->D', 'G->G', 'O->O']|      |      >>> np.remainder.types|      ['bb->b', 'BB->B', 'hh->h', 'HH->H', 'ii->i', 'II->I', 'll->l', 'LL->L',|      'qq->q', 'QQ->Q', 'ff->f', 'dd->d', 'gg->g', 'OO->O']None
"""

4，創建一個10-49的數組，并將其倒序排列

yy = np.arange(10,50,1)
yy
"""
array([10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43,44, 45, 46, 47, 48, 49])
"""

yy_trans = yy[::-1]
yy_trans
"""
array([49, 48, 47, 46, 45, 44, 43, 42, 41, 40, 39, 38, 37, 36, 35, 34, 33,32, 31, 30, 29, 28, 27, 26, 25, 24, 23, 22, 21, 20, 19, 18, 17, 16,15, 14, 13, 12, 11, 10])
"""

5，找到一個數組中不為0的索引

np.nonzero([5,22,10,14,0,2,0,45])
"""
(array([0, 1, 2, 3, 5, 7], dtype=int64),)
"""

6，隨機構造一個3*3矩陣，并打印其中最大與最小值

yy = np.random.random((3,3))
yy
"""
array([[0.20370941, 0.43612091, 0.70595564],[0.24069372, 0.273715  , 0.25698803],[0.19907169, 0.21970853, 0.54037143]])
"""

yy.min()
"""
0.19907168900348726
"""

yy.max()
"""
0.7059556367657052
"""

7，構造一個5*5的矩陣，令其值都為1，并在最外層加上一圈0

yy = np.ones((5,5))
yy
"""
array([[1., 1., 1., 1., 1.],[1., 1., 1., 1., 1.],[1., 1., 1., 1., 1.],[1., 1., 1., 1., 1.],[1., 1., 1., 1., 1.]])
"""

yy_zero = np.pad(yy,pad_width=1,mode='constant',constant_values=0)
yy_zero
"""
array([[0., 0., 0., 0., 0., 0., 0.],[0., 1., 1., 1., 1., 1., 0.],[0., 1., 1., 1., 1., 1., 0.],[0., 1., 1., 1., 1., 1., 0.],[0., 1., 1., 1., 1., 1., 0.],[0., 1., 1., 1., 1., 1., 0.],[0., 0., 0., 0., 0., 0., 0.]])
"""

8，構建一個shape為（6，7，8）的矩陣，并找到第100個元素的索引值

np.unravel_index(100,(6,7,8))
"""
(1, 5, 4)
"""

9，對一個5*5的矩陣做歸一化操作

yy = np.random.random((5,5))
yy
"""
array([[0.94940168, 0.65730346, 0.96278534, 0.75923461, 0.84884701],[0.76622936, 0.36055562, 0.92852778, 0.07413462, 0.49142217],[0.82448018, 0.8047853 , 0.83052986, 0.05108754, 0.9630701 ],[0.04363141, 0.78501252, 0.93953562, 0.47592529, 0.40644514],[0.30959323, 0.16236801, 0.71394387, 0.27592273, 0.99898129]])
"""

yy_max = yy.max()
yy_max
"""
0.9989812852483628
"""

yy_min = yy.min()
yy_min
"""
0.0436314121510083
"""

yy_arr = (yy-yy_min)/(yy_max-yy_min)
yy_arr
"""
array([[0.94810319, 0.6423532 , 0.96211237, 0.7490483 , 0.84284891],[0.75636996, 0.33173627, 0.92625371, 0.03192884, 0.46871912],[0.81734325, 0.79672789, 0.82367567, 0.00780461, 0.96241044],[0.        , 0.77603099, 0.93777603, 0.45249797, 0.37977053],[0.27839205, 0.12428598, 0.70164081, 0.2431479 , 1.        ]])
"""

10，找到兩個數組中相同的值

y1 = np.random.randint(0,10,5)
y1
"""
array([0, 6, 0, 6, 1])
"""

y2 = np.random.randint(0,10,5)
y2
"""
array([9, 6, 9, 1, 7])
"""

y_same = np.intersect1d(y1,y2)
print(y_same)
"""
[1 6]
"""

11，得到今天 明天 昨天的日期

yesterday = np.datetime64('today','D') - np.timedelta64(1,'D')
today = np.datetime64('today','D')
tommorow = np.datetime64('today','D') + np.timedelta64(1,'D')

today
"""
numpy.datetime64('2022-05-01')
"""

tommorow
"""
numpy.datetime64('2022-05-02')
"""

yesterday
"""
numpy.datetime64('2022-04-30')
"""

12，得到一個月中所有的天

np.arange('2022-04','2022-05',dtype='datetime64[D]')
"""
array(['2022-04-01', '2022-04-02', '2022-04-03', '2022-04-04','2022-04-05', '2022-04-06', '2022-04-07', '2022-04-08','2022-04-09', '2022-04-10', '2022-04-11', '2022-04-12','2022-04-13', '2022-04-14', '2022-04-15', '2022-04-16','2022-04-17', '2022-04-18', '2022-04-19', '2022-04-20','2022-04-21', '2022-04-22', '2022-04-23', '2022-04-24','2022-04-25', '2022-04-26', '2022-04-27', '2022-04-28','2022-04-29', '2022-04-30'], dtype='datetime64[D]')
"""

13，得到一個數的整數部分

yy = np.random.uniform(0,10,5)
yy
"""
array([2.90503468, 3.99604344, 3.58371427, 7.85081037, 9.31731275])
"""

np.floor(yy)
"""
array([2., 3., 3., 7., 9.])
"""

14，構造一個數組，讓它不能被改變

yy = np.zeros(3)
yy
"""
array([0., 0., 0.])
"""

yy.flags.writeable = False

yy[0] = 1
"""
---------------------------------------------------------------------------
ValueError                                Traceback (most recent call last)
<ipython-input-43-a3f5f7b6aa0f> in <module>
----> 1 yy[0] = 1ValueError: assignment destination is read-only
"""

15，打印大數據的部分值，全部值

np.set_printoptions(threshold=5)
yy = np.zeros((15,15))
yy
"""
array([[0., 0., 0., ..., 0., 0., 0.],[0., 0., 0., ..., 0., 0., 0.],[0., 0., 0., ..., 0., 0., 0.],...,[0., 0., 0., ..., 0., 0., 0.],[0., 0., 0., ..., 0., 0., 0.],[0., 0., 0., ..., 0., 0., 0.]])
"""

16，找到在一個數組中，最接近一個數的索引

yy = np.arange(100)
yy
"""
array([ 0,  1,  2, ..., 97, 98, 99])
"""

sq = np.random.uniform(0,100)
sq
"""
89.87060277876606
"""

index = (np.abs(yy-sq)).argmin()
print(yy[index])
"""
90
"""

17，32位float類型和32位int類型轉換

yy = np.arange(10,dtype=np.int32)
print(yy.dtype)
"""
int32
"""

yy = yy.astype(np.float32)
print(yy.dtype)
"""
float32
"""

18，打印數組元素位置坐標與數值

yy = np.arange(9).reshape(3,3)
yy
"""
array([[0, 1, 2],[3, 4, 5],[6, 7, 8]])
"""

for index,value in np.ndenumerate(yy):print(index,value)
"""
(0, 0) 0
(0, 1) 1
(0, 2) 2
(1, 0) 3
(1, 1) 4
(1, 2) 5
(2, 0) 6
(2, 1) 7
(2, 2) 8
"""

19，按照數組的某一列進行排序

yy = np.random.randint(0,10,(3,3))
yy
"""
array([[1, 6, 3],[4, 9, 2],[3, 3, 8]])
"""

yy_column = yy[yy[:,1].argsort()]
yy_column
"""
array([[3, 3, 8],[1, 6, 3],[4, 9, 2]])
"""

20，統計數組中每個數值出現的次數

yy = np.array([1,3,4,2,4,1,3,5,2,3,4,5])
np.bincount(yy)
"""
array([0, 2, 2, 3, 3, 2], dtype=int64)
"""

21，對一個四維數組的最后兩維來求和

yy = np.random.randint(0,10,(4,4,4,4))
yy
"""
array([[[[8, 4, 6, 3],[2, 7, 6, 8],[6, 4, 4, 4],[2, 8, 1, 0]],[[2, 8, 8, 7],[9, 1, 3, 2],[0, 5, 3, 1],[2, 9, 4, 9]],[[5, 6, 0, 7],[1, 8, 4, 9],[2, 8, 3, 1],[3, 5, 0, 2]],[[9, 0, 1, 4],[4, 7, 7, 2],[7, 6, 3, 1],[5, 5, 3, 3]]],[[[3, 8, 5, 8],[5, 2, 1, 2],[7, 8, 0, 5],[0, 9, 4, 7]],[[8, 0, 6, 8],[7, 3, 4, 5],[7, 1, 5, 0],[8, 8, 5, 6]],[[0, 7, 5, 4],[4, 3, 4, 7],[7, 4, 7, 3],[8, 5, 8, 6]],[[7, 1, 5, 9],[5, 1, 3, 4],[5, 3, 1, 9],[3, 6, 3, 7]]],[[[6, 6, 8, 3],[5, 6, 1, 0],[7, 8, 5, 4],[7, 2, 8, 5]],[[1, 4, 7, 8],[9, 8, 2, 5],[2, 7, 3, 7],[7, 6, 0, 4]],[[2, 7, 6, 9],[4, 6, 0, 3],[0, 3, 2, 8],[4, 8, 4, 5]],[[1, 2, 7, 6],[4, 0, 5, 3],[5, 6, 0, 0],[2, 8, 3, 3]]],[[[7, 1, 8, 4],[7, 7, 1, 1],[1, 1, 6, 9],[0, 0, 8, 0]],[[1, 9, 8, 2],[5, 0, 5, 0],[1, 3, 8, 1],[6, 2, 2, 4]],[[0, 7, 2, 5],[1, 8, 5, 3],[4, 7, 5, 1],[0, 8, 4, 4]],[[3, 1, 0, 6],[3, 2, 3, 2],[5, 4, 8, 7],[8, 1, 7, 2]]]])
"""

sq = yy.sum(axis=(-2,-1))
sq
"""
array([[73, 73, 64, 67],[74, 81, 82, 72],[81, 80, 71, 55],[61, 57, 64, 62]])
"""

22，交換矩陣中的兩行

yy = np.arange(30).reshape(5,6)
yy
"""
array([[ 0,  1,  2,  3,  4,  5],[ 6,  7,  8,  9, 10, 11],[12, 13, 14, 15, 16, 17],[18, 19, 20, 21, 22, 23],[24, 25, 26, 27, 28, 29]])
"""

yy[[0,1]] = yy[[1,0]]
yy
"""
array([[ 6,  7,  8,  9, 10, 11],[ 0,  1,  2,  3,  4,  5],[12, 13, 14, 15, 16, 17],[18, 19, 20, 21, 22, 23],[24, 25, 26, 27, 28, 29]])
"""

23，找到一個數組中最常出現的數字

yy = np.random.randint(0,20,5)
print(yy)
"""
[18 14 16  8 18]
"""

yy_often = np.bincount(yy).argmax()
yy_often
"""
18
"""

24，快速查找TOP K

yy = np.arange(10000)
yy
"""
array([   0,    1,    2, ..., 9997, 9998, 9999])
"""

np.random.shuffle(yy)
yy
"""
array([9434, 5915, 7866, ..., 7133, 5724, 2156])
"""

n = 5
yy_top = yy[np.argpartition(-yy,n)[:n]]
yy_top
"""
array([9999, 9997, 9998, 9996, 9995])
"""

25，去除掉一個數組中，所有元素都相同的數據

a = np.array([1,2,3,4])
b = np.array([1,2,3,5])
np.all(a == b)
"""
False
"""

np.any(a == b)
"""
True
"""