{"id":69,"date":"2019-10-19T15:16:53","date_gmt":"2019-10-19T13:16:53","guid":{"rendered":"http:\/\/market-and-us.com\/blog\/?p=69"},"modified":"2019-11-02T15:56:20","modified_gmt":"2019-11-02T14:56:20","slug":"how-to-code-basic-stock-scanner","status":"publish","type":"post","link":"https:\/\/market-and-us.com\/blog\/how-to-code-basic-stock-scanner-69\/","title":{"rendered":"How to code a basic stock scanner?"},"content":{"rendered":"\n

After writing the code for a basic backtest<\/a> I got the feedback that a stock scanner would be useful<\/strong> to find the signals validated with backtests. And here it is: The instructions how to code a stock scanner.
In the first steps we use only one stock<\/strong> for backtesting or scanning. Because for scanning the whole market you will need all the data for 500 (S&P 500) or 6000-8000 stocks. In my opinion you can do that just with a server running the data loading over night.<\/p>\n\n\n\n

But now let’s start with our little scan code:<\/p>\n\n\n\n

Getting the stock data<\/h2>\n\n\n\n

Like for the backtest we need to download or import the stock data<\/strong> as csv-file. I could present you a file on my blog server but that wouldn’t make sense because you want to scan the stock for the current day and for tomorrow, …
Therefore we need a solution to get the daily data for a stock symbol<\/strong>. Again you can use the data of your broker or other free or cheap APIs. For our example I will use a manual method. You will learn automatic methods later for loading many stocks without “doing” anything.<\/p>\n\n\n\n

The 4 steps to download historical data online:<\/h3>\n\n\n\n
  1. Visit the Yahoo Finance website<\/a>.<\/li>
  2. Click in the search field at the top and type your stock symbol (e.g. GE).<\/li>
  3. Click on the tab Historical Data.<\/li>
  4. The time period is already set to a year and the frequency to daily data, so you just click the “Download Data”-link to get your csv-file.<\/li><\/ol>\n\n\n\n

    If you have problems getting the data<\/strong> (or anything changed with the Yahoo Finance services) write me a comment below and download a sample file here<\/a>.<\/p>\n\n\n\n

    Loading data in variable<\/h2>\n\n\n\n

    Like in the last article we use the library pandas<\/span><\/code> for the financial calculations<\/span>:<\/p>\n\n\n\n

    import pandas as pd\ndata = pd.read_csv(\"GE.csv\")<\/code><\/pre>\n\n\n\n
    And during the coding process it’s always interesting to get the first and the last lines for checking the content<\/span>:<\/p>\n\n\n\n
    print(data.head())\nprint(data.tail())<\/code><\/pre>\n\n\n\n
    Setting up the strategy<\/h2>\n\n\n\n
    I am sure you’re interested in other indicators<\/span> than the SMA and you want to code strategies with EMA, stochastics, MACD, ATR<\/span> and many others. Am I right?
    But that’s complex and I have to explain you how to use a function with a DataFrame<\/code> (the variable type of the pandas<\/code> library). So you have to wait for the next articles.<\/p>\n\n\n\n
    Our strategy is still with two simple moving averages crossing<\/span> each other. But we will add the form of the candle.<\/p>\n\n\n\n
    Please notice: The strategies in the basic articles are not to make money. They are just examples for our code!<\/strong><\/p><\/blockquote>\n\n\n\n
    Crossing of two moving averages<\/h3>\n\n\n\n
    Here the 20 and the 50 SMA<\/span><\/p>\n\n\n\n
    data['SMA20'] = data.Close.rolling(20).mean()\ndata['SMA50'] = data.Close.rolling(50).mean()<\/code><\/pre>\n\n\n\n
    and the crossing variables<\/span> for long and short positions:<\/p>\n\n\n\n
    data['long']  = (data.SMA20 > data.SMA50) & (data.SMA20.shift(1) <= data.SMA50.shift(1))\ndata['short'] = (data.SMA20 < data.SMA50) & (data.SMA50.shift(1) >= data.SMA50.shift(1)) <\/code><\/pre>\n\n\n\n
    Now you will get the long-signal, when the 20 SMA is above the 50 SMA and the 20 SMA was below the 50 SMA the day before<\/strong>.<\/p>\n\n\n\n
    Green body bigger than the last five bodies<\/h3>\n\n\n\n
    To add the condition for a green candle with a body bigger than the body of the last 5 candles<\/span> (red candle for the short signal) you do not have to set it for the whole dataset. It’s much easier to write it for the last line:<\/p>\n\n\n\n
    lastrow  = data.iloc[-1]\ngreen    = lastrow.Close > lastrow.Open\nred      = lastrow.Open > lastrow.Close\nmaxBody5 = (df.Close.iloc[-5:] - df.Open.iloc[-5:]).abs().max()\nbigbody  = abs(lastrow.Close - lastrow.Open) > maxBody5<\/code><\/pre>\n\n\n\n
    The lastrow<\/code> is checked for a green<\/code> body. And then the biggest body of the last 5 candles (maxBody5<\/code>) is compared with the current body, resulting in the variable bigbody<\/code>.<\/p>\n\n\n\n
    Scan the stock<\/h2>\n\n\n\n
    To scan the stock<\/span> (here GE<\/strong>) wether our strategy is showing us an entry signal or not, you can simply type:<\/p>\n\n\n\n
    long_signal  = data['long'].iloc[-1]  and green and bigbody\nshort_signal = data['short'].iloc[-1] and red   and bigbody<\/code><\/pre>\n\n\n\n
    Output of the result<\/h2>\n\n\n\n
    The last step is to show the result<\/span>. And you just write:<\/p>\n\n\n\n
    if long_signal:\n    print(\"Today there's a buy signal for GE.\")\nelif short_signal:\n    print(\"Today there's a short signal for GE.\")\nelse:\n    print(\"No signals for GE today.\")<\/code><\/pre>\n\n\n\n
    That’s it. I hope again you learned some coding possibilities with this articles to open the world for all your ideas one step more.<\/p>\n\n\n\n
    Tell me<\/strong> what you like and what not, what’s missing and where you had problems. I will help you<\/strong> in the comments section to get your program done.
    Good results for your scans, huge profits with your strategy development and fun with your coding!<\/p>\n","protected":false},"excerpt":{"rendered":"
    After writing the code for a basic backtest I got the feedback that a stock scanner would be useful to find the signals validated with backtests. And here it is: The instructions how to code a stock scanner.In the first steps we use only one stock for backtesting or scanning. Because for scanning the whole […]<\/p>\n","protected":false},"author":1,"featured_media":83,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"yasr_overall_rating":0,"yasr_post_is_review":"","yasr_auto_insert_disabled":"","yasr_review_type":""},"categories":[7],"tags":[26,20,32,25,33,22,21,27,28,23,29,30],"yoast_head":"\nHow to code a basic stock scanner? - The Market and Us<\/title>\n<meta name=\"description\" content=\"In this article you will learn how to code a basic stock scanner. 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