Why am I getting list elements < 0 ? - Printable Version +- Python Forum (https://python-forum.io) +-- Forum: Python Coding (https://python-forum.io/forum-7.html) +--- Forum: General Coding Help (https://python-forum.io/forum-8.html) +--- Thread: Why am I getting list elements < 0 ? (/thread-34701.html) |
Why am I getting list elements < 0 ? - Mark17 - Aug-23-2021 Hi all! Here's some code: price_chg = np.arange(-10,11,2) stock_prices = [100] for i in range(10001): if (stock_prices[-1] + np.random.choice(price_chg)) < 0: stock_prices.append(0) continue else: stock_prices.append(stock_prices[-1] + np.random.choice(price_chg))Why is the if block failing to keep negative integers out of the list? RE: Why am I getting list elements < 0 ? - ibreeden - Aug-23-2021 (Aug-23-2021, 02:10 PM)Mark17 Wrote: Why is the if block failing to keep negative integers out of the list?Because you are generating a new random price in the "else" block which can again be negative. Apparently you mean to do this: price_chg = np.arange(-10,11,2) stock_prices = [100] for i in range(10001): random_price = stock_prices.append(stock_prices[-1] + np.random.choice(price_chg)) if random_price < 0: stock_prices.append(0) else: stock_prices.append(random_price) RE: Why am I getting list elements < 0 ? - Mark17 - Aug-23-2021 (Aug-23-2021, 02:44 PM)ibreeden Wrote:(Aug-23-2021, 02:10 PM)Mark17 Wrote: Why is the if block failing to keep negative integers out of the list?Because you are generating a new random price in the "else" block which can again be negative. When will the "stupid mistakes" end? Rhetorical question. :) Thank you! RE: Why am I getting list elements < 0 ? - deanhystad - Aug-23-2021 max() may be a better choice. import random price = 10 stock_prices = [price] for _ in range(11): price = max(0, price + random.randrange(-10, 11, 2)) stock_prices.append(price) print(stock_prices) RE: Why am I getting list elements < 0 ? - naughtyCat - Aug-24-2021 One line code import random stock_prices = [10] + [max(0, 10+random.randrange(-10, 11, 2)) for _ in range(11)] RE: Why am I getting list elements < 0 ? - deanhystad - Aug-24-2021 Not the same result. +/-10 is the range of daily fluctuation, not the range of stock_prices. RE: Why am I getting list elements < 0 ? - naughtyCat - Aug-24-2021 (Aug-24-2021, 08:31 AM)deanhystad Wrote: Not the same result. +/-10 is the range of daily fluctuation, not the range of stock_prices. two line import random price = 10 stock_prices = [price] + [max(0, price+random.randrange(-10, 11, 2)) for _ in range(11)] RE: Why am I getting list elements < 0 ? - deanhystad - Aug-24-2021 Still not right. The price fluctuates from the previous day, not the first day. I don't think this can be done with a comprehension because there is no mechanism for remembering what the price was yesterday. RE: Why am I getting list elements < 0 ? - naughtyCat - Aug-26-2021 (Aug-24-2021, 03:32 PM)deanhystad Wrote: Still not right. The price fluctuates from the previous day, not the first day. I don't think this can be done with a comprehension because there is no mechanism for remembering what the price was yesterday. ya, you are right, I am learned, thanks |