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How to efficiently access a Python iterable indexes provenient from another iterable


How to efficiently access a Python iterable indexes provenient from another iterable

By : Doctor
Date : November 21 2020, 03:00 PM
I wish this help you Since operator.itemgetter accepts multiple indices, one solution is:
code :
>>> import operator
>>> operator.itemgetter(*Y)(X)
('b', 'd', 'e', 'a', 'c')
np.array(X)[Y]
# setup
import random
import numpy as np
X = [random.randint(0,100) for i in range(1000000)]
Y = [random.randint(0,1000000) for i in range(1000)]
%timeit [X[i] for i in Y]
10000 loops, best of 3: 34 µs per loop
%timeit operator.itemgetter(*Y)(X)
100000 loops, best of 3: 16.6 µs per loop
%timeit np.array(X)[Y]
10 loops, best of 3: 31.6 ms per loop
x = np.array(X)
y = np.array(Y)
%timeit x[y]
1000000 loops, best of 3: 1.72 µs per loop


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python make class iterable by returning embedded iterable

python make class iterable by returning embedded iterable


By : Jasmine Wiggins
Date : March 29 2020, 07:55 AM
it helps some times I have a class in python, which has an iterable as instance variable. I want to iterate the instances of the class by iterating over the embedded iterable. , The "best" way to way to delegate __iter__ would be:
code :
def __iter__(self):
    return iter(self._iterable)
def __iter__(self):
    for item in self._iterable:
        yield item
def __iter__(self):
    yield from self._iterable
def __init__(self, iterable):
    self.__iter__ = iterable.__iter__
class SurprisingIter(object):
    def __init__(self):
        self.__iter__ = lambda self: iter("abc")

    def __iter__(self):
        return iter([1, 2, 3])
Python any(iterable) and all(iterable) without short-circuiting and with side-effects

Python any(iterable) and all(iterable) without short-circuiting and with side-effects


By : Hashim
Date : March 29 2020, 07:55 AM
wish helps you I have the following code: , How about simply
code :
reduce(operator.and_, seq)
reduce(operator.or_, seq)
Boost Python iterable convertible masking non-iterable constructor

Boost Python iterable convertible masking non-iterable constructor


By : mchomvu
Date : March 29 2020, 07:55 AM
Does that help It looks like a bug to me. As best as I can tell, the dispatch is not properly handling the return from the convertible check. Additionally, I observe different results by changing the order in which constructors are registered (either via boost::python::init or boost::python::make_constructor()).
For example, with a setup similar to the problem described in the question, the following produces similar results:
code :
BOOST_PYTHON_MODULE(example)
{
  namespace python = boost::python;

  // ...

  python::class_<spam>("Spam", python::no_init)
    .def(python::init<int>())
    .def(python::init<std::vector<int> >())
    ;
}
>>> import example
>>> spam = example.Spam(42)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'int' object is not iterable
>>> spam = example.Spam([42])
BOOST_PYTHON_MODULE(example)
{
  namespace python = boost::python;

  // ...

  python::class_<spam>("Spam", python::no_init)
    .def(python::init<std::vector<int> >())
    .def(python::init<int>())
    ;
}
>>> import example
>>> spam = example.Spam(42)
>>> spam = example.Spam([42])
#include <vector>
#include <boost/python.hpp>
#include <boost/python/stl_iterator.hpp>

/// @brief Type that allows for registration of conversions from
///        python iterable types.
struct iterable_converter
{
  /// @note Registers converter from a python interable type to the
  ///       provided type.
  template <typename Container>
  iterable_converter&
  from_python()
  {
    boost::python::converter::registry::push_back(
      &iterable_converter::convertible,
      &iterable_converter::construct<Container>,
      boost::python::type_id<Container>());
    return *this;
  }

  /// @brief Check if PyObject is iterable.
  static void* convertible(PyObject* object)
  {
    return PyObject_GetIter(object) ? object : NULL;
  }

  /// @brief Convert iterable PyObject to C++ container type.
  ///
  /// Container Concept requirements:
  ///
  ///   * Container::value_type is CopyConstructable.
  ///   * Container can be constructed and populated with two iterators.
  ///     I.e. Container(begin, end)
  template <typename Container>
  static void construct(
    PyObject* object,
    boost::python::converter::rvalue_from_python_stage1_data* data)
  {
    namespace python = boost::python;
    // Object is a borrowed reference, so create a handle indicting it is
    // borrowed for proper reference counting.
    python::handle<> handle(python::borrowed(object));

    // Obtain a handle to the memory block that the converter has allocated
    // for the C++ type.
    typedef python::converter::rvalue_from_python_storage<Container>
                                                                 storage_type;
    void* storage = reinterpret_cast<storage_type*>(data)->storage.bytes;

    typedef python::stl_input_iterator<typename Container::value_type>
                                                                     iterator;

    // Allocate the C++ type into the converter's memory block, and assign
    // its handle to the converter's convertible variable.  The C++
    // container is populated by passing the begin and end iterators of
    // the python object to the container's constructor.
    data->convertible = new (storage) Container(
      iterator(python::object(handle)), // begin
      iterator());                      // end
  }
};

/// @brief Mockup class.
struct spam
{
  explicit spam(const std::vector<int>&) {}
};

BOOST_PYTHON_MODULE(_example)
{
  namespace python = boost::python;

  // Register interable conversions.
  iterable_converter()
    .from_python<std::vector<int> >()
    ;

  // Expose Spam with a single constructor.  It will be adapted.
  python::class_<spam>("Spam", python::init<std::vector<int> >());
}
from _example import *

def _patched_spam_init():
    ''' Monkey-patch Spam.__init__ to force the first argument to be
        iterable.

    '''
    # Get handle to delegate.
    _Spam_init = Spam.__init__

    # Patched method that delegates to the original.
    def patch(self, value):
        try:
            (x for x in value)
        except TypeError:
            value = [value]
        return _Spam_init(self, value)

    # Set __init__ to the patched method.
    Spam.__init__ = patch

_patched_spam_init()
>>> import example
>>> spam = example.Spam(42)
>>> spam = example.Spam([42])
collections.Iterable vs typing.Iterable in type annotation and checking for Iterable

collections.Iterable vs typing.Iterable in type annotation and checking for Iterable


By : John
Date : March 29 2020, 07:55 AM
it should still fix some issue The typing.Iterable is generic, so you can say what it's an iterable of in your type annotations, e.g. Iterable[int] for an iterable of ints.
The collections iterable is an abstract base class. These can include extra mixin methods to make the interface easier to implement when you create your own subclasses.
Object not iterable in python when created made class iterable for objects

Object not iterable in python when created made class iterable for objects


By : user3293997
Date : March 29 2020, 07:55 AM
it helps some times I am making a program where I need to iterate through every option in a class to perform actions to each object, to do that I made an 'IterRegistry' Class to turn the metaclass of my objects to iterable but for some reason, it still isn't working. , Declaring a class metaclass like this:
code :
class TreeLine(object):
    __metaclass__ = IterRegistry
class TreeLine(metaclass=IterRegistry):
    ...
>>> class M(type):pass
... 
>>> class C:
...     __metaclass__ = M
... 
>>> type(C)
<class 'type'>
>>> class D(metaclass=M):pass
... 
>>> type(D)
<class '__main__.M'>
>>> 
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