Useful snippets

group.py

import itertools as it
def group(iterable, size, fill=None):
    yield from it.zip_longest(*[iter(iterable)] * size, fillvalue=fill)

if __name__ == '__main__':
    print(*group(range(10), 3, 0), sep=', ') # -> (0, 1, 2), (3, 4, 5), (6, 7, 8), (9, 0, 0)

reverse.cpp

#include <iostream>  // For main
#include <vector>    // For main

template <typename T>
struct reversion_wrapper { T& iterable; };

template <typename T>
auto begin(reversion_wrapper<T>& w) { return std::rbegin(w.iterable); }
    
template <typename T>
auto end(reversion_wrapper<T>& w) { return std::rend(w.iterable); }

template <typename T>
auto rbegin(reversion_wrapper<T>& w) { return std::begin(w.iterable); }

template <typename T>
auto rend(reversion_wrapper<T>& w) { return std::end(w.iterable); }

template <typename T>
reversion_wrapper<T> reverse(T&& iterable) { return { iterable }; }

int main() {
    std::vector<int> v {1, 2, 3, 4, 5, 6, 7};
    for (auto&& i: v) {
        std::cout << i << ' ';
    }
    std::cout << '\n';
    for (auto&& i: reverse(v)) {
        std::cout << i << ' ';
    }
    /*
     * Output:
     * 1 2 3 4 5 6 7
     * 7 6 5 4 3 2 1
     */
}

transpose.py

import itertools as it
def transpose(iterable, fill=None):
    yield from it.zip_longest(*iterable, fillvalue=fill)

if __name__ == '__main__':
    print(*transpose([
        (1, 2, 3),
        (4, 5, 6), 
        (7, 8, 9)
    ]), sep=', ') # (1, 4, 7),
    #               (2, 5, 8),
    #               (3, 6, 9)