PyCon 2019 Banksalad event code

calculator.py

from itertools import permutations


def permutate(cards, n, func):
    for p in permutations(cards, n):
        try:
            yield eval(func(p)), p
        except Exception as e:
            pass


def only_numbers(result):
    value, p = result
    return isinstance(value, (int, float))


def calc(cards, n=None, pre_format=None):
    if n is None:
        n = len(cards)
    if pre_format is None:
        pre_format = '{}' * n

    func = lambda p: pre_format.format(*p)
    seq = list(filter(only_numbers, permutate(cards, n, func)))
    if not seq:
        print('Cannot calculate!')
        return

    for m_func in (min, max):
        value, p = m_func(seq)
        print(func(p), '→', value)

    available = sorted(set(v for v, _ in seq))
    print('available:', available)

case.py

from calculator import calc


if __name__ == '__main__':
    cards = ['<', '>', '10', '30', '50', '70', '90', 'i', '==']
    pre_format = 'sum([int(i {} {}) for i in range({}, {})])'
    calc(cards, n=4, pre_format=pre_format)

    cards = ['0', '0.1', '0.5', '1', '2', '3', '4', 'x', 'y']
    pre_format = '{} ** len(str(sum({} for _ in range({}))))'
    calc(cards, n=3, pre_format=pre_format)

    cards = ['bin', '4', '"10101"', '2', '16', '8', '"0xff"', '"0o76"', '0']
    pre_format = 'int({}, {})'
    calc(cards, n=2, pre_format=pre_format)

    cards = ['2', '3', '4', '*', '*', '"1"', '"2"', '"3"', '"4"']
    calc(cards, n=5)

    cards = ['3', '5', '*', 'sum', 'range']
    pre_format = '{}(x{}{} for x in {}({}))'
    calc(cards, pre_format=pre_format)

    cards = ['ord', 'min', 'len', '"banksalad"', '"pycon"', '*']
    pre_format = '{}({}({})){}{}({})'
    calc(cards, pre_format=pre_format)

    cards = ['sum', 'range', '+', '*', '2', '4', '8']
    pre_format = '-pow({}({}({})), {})'
    calc(cards, n=4, pre_format=pre_format)

    cards = ['+', '-', '*', '/', '7', '6', '5', '4', 'None']
    calc(cards, n=5)