diff options
Diffstat (limited to 'numpy/doc/glossary.py')
| -rw-r--r-- | numpy/doc/glossary.py | 475 |
1 files changed, 0 insertions, 475 deletions
diff --git a/numpy/doc/glossary.py b/numpy/doc/glossary.py deleted file mode 100644 index 31130559b..000000000 --- a/numpy/doc/glossary.py +++ /dev/null @@ -1,475 +0,0 @@ -""" -======== -Glossary -======== - -.. glossary:: - - along an axis - Axes are defined for arrays with more than one dimension. A - 2-dimensional array has two corresponding axes: the first running - vertically downwards across rows (axis 0), and the second running - horizontally across columns (axis 1). - - Many operations can take place along one of these axes. For example, - we can sum each row of an array, in which case we operate along - columns, or axis 1:: - - >>> x = np.arange(12).reshape((3,4)) - - >>> x - array([[ 0, 1, 2, 3], - [ 4, 5, 6, 7], - [ 8, 9, 10, 11]]) - - >>> x.sum(axis=1) - array([ 6, 22, 38]) - - array - A homogeneous container of numerical elements. Each element in the - array occupies a fixed amount of memory (hence homogeneous), and - can be a numerical element of a single type (such as float, int - or complex) or a combination (such as ``(float, int, float)``). Each - array has an associated data-type (or ``dtype``), which describes - the numerical type of its elements:: - - >>> x = np.array([1, 2, 3], float) - - >>> x - array([ 1., 2., 3.]) - - >>> x.dtype # floating point number, 64 bits of memory per element - dtype('float64') - - - # More complicated data type: each array element is a combination of - # and integer and a floating point number - >>> np.array([(1, 2.0), (3, 4.0)], dtype=[('x', int), ('y', float)]) - array([(1, 2.0), (3, 4.0)], - dtype=[('x', '<i4'), ('y', '<f8')]) - - Fast element-wise operations, called a :term:`ufunc`, operate on arrays. - - array_like - Any sequence that can be interpreted as an ndarray. This includes - nested lists, tuples, scalars and existing arrays. - - attribute - A property of an object that can be accessed using ``obj.attribute``, - e.g., ``shape`` is an attribute of an array:: - - >>> x = np.array([1, 2, 3]) - >>> x.shape - (3,) - - big-endian - When storing a multi-byte value in memory as a sequence of bytes, the - sequence addresses/sends/stores the most significant byte first (lowest - address) and the least significant byte last (highest address). Common in - micro-processors and used for transmission of data over network protocols. - - BLAS - `Basic Linear Algebra Subprograms <https://en.wikipedia.org/wiki/Basic_Linear_Algebra_Subprograms>`_ - - broadcast - NumPy can do operations on arrays whose shapes are mismatched:: - - >>> x = np.array([1, 2]) - >>> y = np.array([[3], [4]]) - - >>> x - array([1, 2]) - - >>> y - array([[3], - [4]]) - - >>> x + y - array([[4, 5], - [5, 6]]) - - See `numpy.doc.broadcasting` for more information. - - C order - See `row-major` - - column-major - A way to represent items in a N-dimensional array in the 1-dimensional - computer memory. In column-major order, the leftmost index "varies the - fastest": for example the array:: - - [[1, 2, 3], - [4, 5, 6]] - - is represented in the column-major order as:: - - [1, 4, 2, 5, 3, 6] - - Column-major order is also known as the Fortran order, as the Fortran - programming language uses it. - - decorator - An operator that transforms a function. For example, a ``log`` - decorator may be defined to print debugging information upon - function execution:: - - >>> def log(f): - ... def new_logging_func(*args, **kwargs): - ... print("Logging call with parameters:", args, kwargs) - ... return f(*args, **kwargs) - ... - ... return new_logging_func - - Now, when we define a function, we can "decorate" it using ``log``:: - - >>> @log - ... def add(a, b): - ... return a + b - - Calling ``add`` then yields: - - >>> add(1, 2) - Logging call with parameters: (1, 2) {} - 3 - - dictionary - Resembling a language dictionary, which provides a mapping between - words and descriptions thereof, a Python dictionary is a mapping - between two objects:: - - >>> x = {1: 'one', 'two': [1, 2]} - - Here, `x` is a dictionary mapping keys to values, in this case - the integer 1 to the string "one", and the string "two" to - the list ``[1, 2]``. The values may be accessed using their - corresponding keys:: - - >>> x[1] - 'one' - - >>> x['two'] - [1, 2] - - Note that dictionaries are not stored in any specific order. Also, - most mutable (see *immutable* below) objects, such as lists, may not - be used as keys. - - For more information on dictionaries, read the - `Python tutorial <https://docs.python.org/tutorial/>`_. - - field - In a :term:`structured data type`, each sub-type is called a `field`. - The `field` has a name (a string), a type (any valid dtype), and - an optional `title`. See :ref:`arrays.dtypes` - - Fortran order - See `column-major` - - flattened - Collapsed to a one-dimensional array. See `numpy.ndarray.flatten` - for details. - - homogeneous - Describes a block of memory comprised of blocks, each block comprised of - items and of the same size, and blocks are interpreted in exactly the - same way. In the simplest case each block contains a single item, for - instance int32 or float64. - - immutable - An object that cannot be modified after execution is called - immutable. Two common examples are strings and tuples. - - instance - A class definition gives the blueprint for constructing an object:: - - >>> class House: - ... wall_colour = 'white' - - Yet, we have to *build* a house before it exists:: - - >>> h = House() # build a house - - Now, ``h`` is called a ``House`` instance. An instance is therefore - a specific realisation of a class. - - iterable - A sequence that allows "walking" (iterating) over items, typically - using a loop such as:: - - >>> x = [1, 2, 3] - >>> [item**2 for item in x] - [1, 4, 9] - - It is often used in combination with ``enumerate``:: - >>> keys = ['a','b','c'] - >>> for n, k in enumerate(keys): - ... print("Key %d: %s" % (n, k)) - ... - Key 0: a - Key 1: b - Key 2: c - - itemsize - The size of the dtype element in bytes. - - list - A Python container that can hold any number of objects or items. - The items do not have to be of the same type, and can even be - lists themselves:: - - >>> x = [2, 2.0, "two", [2, 2.0]] - - The list `x` contains 4 items, each which can be accessed individually:: - - >>> x[2] # the string 'two' - 'two' - - >>> x[3] # a list, containing an integer 2 and a float 2.0 - [2, 2.0] - - It is also possible to select more than one item at a time, - using *slicing*:: - - >>> x[0:2] # or, equivalently, x[:2] - [2, 2.0] - - In code, arrays are often conveniently expressed as nested lists:: - - - >>> np.array([[1, 2], [3, 4]]) - array([[1, 2], - [3, 4]]) - - For more information, read the section on lists in the `Python - tutorial <https://docs.python.org/tutorial/>`_. For a mapping - type (key-value), see *dictionary*. - - little-endian - When storing a multi-byte value in memory as a sequence of bytes, the - sequence addresses/sends/stores the least significant byte first (lowest - address) and the most significant byte last (highest address). Common in - x86 processors. - - mask - A boolean array, used to select only certain elements for an operation:: - - >>> x = np.arange(5) - >>> x - array([0, 1, 2, 3, 4]) - - >>> mask = (x > 2) - >>> mask - array([False, False, False, True, True]) - - >>> x[mask] = -1 - >>> x - array([ 0, 1, 2, -1, -1]) - - masked array - Array that suppressed values indicated by a mask:: - - >>> x = np.ma.masked_array([np.nan, 2, np.nan], [True, False, True]) - >>> x - masked_array(data = [-- 2.0 --], - mask = [ True False True], - fill_value = 1e+20) - - >>> x + [1, 2, 3] - masked_array(data = [-- 4.0 --], - mask = [ True False True], - fill_value = 1e+20) - - - Masked arrays are often used when operating on arrays containing - missing or invalid entries. - - matrix - A 2-dimensional ndarray that preserves its two-dimensional nature - throughout operations. It has certain special operations, such as ``*`` - (matrix multiplication) and ``**`` (matrix power), defined:: - - >>> x = np.mat([[1, 2], [3, 4]]) - >>> x - matrix([[1, 2], - [3, 4]]) - - >>> x**2 - matrix([[ 7, 10], - [15, 22]]) - - method - A function associated with an object. For example, each ndarray has a - method called ``repeat``:: - - >>> x = np.array([1, 2, 3]) - >>> x.repeat(2) - array([1, 1, 2, 2, 3, 3]) - - ndarray - See *array*. - - record array - An :term:`ndarray` with :term:`structured data type` which has been - subclassed as ``np.recarray`` and whose dtype is of type ``np.record``, - making the fields of its data type to be accessible by attribute. - - reference - If ``a`` is a reference to ``b``, then ``(a is b) == True``. Therefore, - ``a`` and ``b`` are different names for the same Python object. - - row-major - A way to represent items in a N-dimensional array in the 1-dimensional - computer memory. In row-major order, the rightmost index "varies - the fastest": for example the array:: - - [[1, 2, 3], - [4, 5, 6]] - - is represented in the row-major order as:: - - [1, 2, 3, 4, 5, 6] - - Row-major order is also known as the C order, as the C programming - language uses it. New NumPy arrays are by default in row-major order. - - self - Often seen in method signatures, ``self`` refers to the instance - of the associated class. For example: - - >>> class Paintbrush: - ... color = 'blue' - ... - ... def paint(self): - ... print("Painting the city %s!" % self.color) - ... - >>> p = Paintbrush() - >>> p.color = 'red' - >>> p.paint() # self refers to 'p' - Painting the city red! - - slice - Used to select only certain elements from a sequence: - - >>> x = range(5) - >>> x - [0, 1, 2, 3, 4] - - >>> x[1:3] # slice from 1 to 3 (excluding 3 itself) - [1, 2] - - >>> x[1:5:2] # slice from 1 to 5, but skipping every second element - [1, 3] - - >>> x[::-1] # slice a sequence in reverse - [4, 3, 2, 1, 0] - - Arrays may have more than one dimension, each which can be sliced - individually: - - >>> x = np.array([[1, 2], [3, 4]]) - >>> x - array([[1, 2], - [3, 4]]) - - >>> x[:, 1] - array([2, 4]) - - structure - See :term:`structured data type` - - structured data type - A data type composed of other datatypes - - subarray data type - A :term:`structured data type` may contain a :term:`ndarray` with its - own dtype and shape: - - >>> dt = np.dtype([('a', np.int32), ('b', np.float32, (3,))]) - >>> np.zeros(3, dtype=dt) - array([(0, [0., 0., 0.]), (0, [0., 0., 0.]), (0, [0., 0., 0.])], - dtype=[('a', '<i4'), ('b', '<f4', (3,))]) - - title - In addition to field names, structured array fields may have an - associated :ref:`title <titles>` which is an alias to the name and is - commonly used for plotting. - - tuple - A sequence that may contain a variable number of types of any - kind. A tuple is immutable, i.e., once constructed it cannot be - changed. Similar to a list, it can be indexed and sliced:: - - >>> x = (1, 'one', [1, 2]) - >>> x - (1, 'one', [1, 2]) - - >>> x[0] - 1 - - >>> x[:2] - (1, 'one') - - A useful concept is "tuple unpacking", which allows variables to - be assigned to the contents of a tuple:: - - >>> x, y = (1, 2) - >>> x, y = 1, 2 - - This is often used when a function returns multiple values: - - >>> def return_many(): - ... return 1, 'alpha', None - - >>> a, b, c = return_many() - >>> a, b, c - (1, 'alpha', None) - - >>> a - 1 - >>> b - 'alpha' - - ufunc - Universal function. A fast element-wise, :term:`vectorized - <vectorization>` array operation. Examples include ``add``, ``sin`` and - ``logical_or``. - - vectorization - Optimizing a looping block by specialized code. In a traditional sense, - vectorization performs the same operation on multiple elements with - fixed strides between them via specialized hardware. Compilers know how - to take advantage of well-constructed loops to implement such - optimizations. NumPy uses :ref:`vectorization <whatis-vectorization>` - to mean any optimization via specialized code performing the same - operations on multiple elements, typically achieving speedups by - avoiding some of the overhead in looking up and converting the elements. - - view - An array that does not own its data, but refers to another array's - data instead. For example, we may create a view that only shows - every second element of another array:: - - >>> x = np.arange(5) - >>> x - array([0, 1, 2, 3, 4]) - - >>> y = x[::2] - >>> y - array([0, 2, 4]) - - >>> x[0] = 3 # changing x changes y as well, since y is a view on x - >>> y - array([3, 2, 4]) - - wrapper - Python is a high-level (highly abstracted, or English-like) language. - This abstraction comes at a price in execution speed, and sometimes - it becomes necessary to use lower level languages to do fast - computations. A wrapper is code that provides a bridge between - high and the low level languages, allowing, e.g., Python to execute - code written in C or Fortran. - - Examples include ctypes, SWIG and Cython (which wraps C and C++) - and f2py (which wraps Fortran). - -""" |