Order matching

order_matching.py

from collections import deque, namedtuple
from random import randint, random


class Order:
    def __init__(self, sum, price, type):
        self.sum = sum
        self.price = price
        self.type = type
        self.status = 'new'

    def __str__(self):
        return f'[{self.status}|{self.type}] {self.sum}@{self.price}'


book = {'sell': deque(), 'buy': deque()}

for i in range(10):
    book['buy'].append(Order(randint(50, 100), 1 + random(), 'buy'))
    book['sell'].append(Order(randint(50, 100), 2 + random(), 'sell'))


def trade_orders(order1, order2):
    trade_amount = min(order1.sum, order2.sum)
    order1.sum -= trade_amount
    order2.sum -= trade_amount
    if order1.sum == 0:
        order1.status = 'completed'
    if order2.sum == 0:
        order2.status = 'completed'
    return order1, order2


def place_order(order):
    counter_type = 'buy' if order.type == 'sell' else 'sell'
    counter_orders = book.get(counter_type, [])
    for i, o in enumerate(counter_orders):
        if counter_type == 'sell' and o.price <= order.price:
            trade_orders(order, counter_orders[i])
        elif counter_type == 'buy' and o.price >= order.price:
            trade_orders(order, counter_orders[i])
        if order.status == 'completed':
            return
    else:
        book[counter_type].append(order)


place_order(Order(128, 2.5, 'buy'))
print(*(str(o) for o in book['sell'] if o.status == 'completed'))