{"id":11187,"date":"2019-12-06T08:05:18","date_gmt":"2019-12-06T13:05:18","guid":{"rendered":"https:\/\/blogs.mathworks.com\/pick\/?p=11187"},"modified":"2019-12-06T08:05:18","modified_gmt":"2019-12-06T13:05:18","slug":"py_addpath","status":"publish","type":"post","link":"https:\/\/blogs.mathworks.com\/pick\/2019\/12\/06\/py_addpath\/","title":{"rendered":"Py_Addpath"},"content":{"rendered":"
\n <\/p>\n

Sean<\/a>‘s pick this week is py_addpath<\/tt> directory matlab_too<\/a> by Eric Fields<\/a>.\n <\/p>\n

<\/introduction><\/p>\n

Using Python with MATLAB<\/a><\/h3>\n

Do you have some Python code from a colleague or a snippet from GitHub that you’d like to use in MATLAB and not have to rewrite it? You can do that through the Python Interface<\/a> for MATLAB.\n <\/p>\n

A simple “hello world” example is as follows:<\/p>\n

s = py.str(\"hello world\"<\/span>) % Convert MATLAB string to py.str<\/span>\r\nwhos s<\/span>\r\nsc = string(capitalize(s)) % Convert capitalized str back to MATLAB string<\/span><\/pre>\n
s = \r\n  Python str with no properties.\r\n\r\n    hello world\r\n  Name      Size            Bytes  Class     Attributes\r\n\r\n  s         1x11                8  py.str              \r\n\r\nsc = \r\n    \"Hello world\"\r\n<\/pre>\n
Now what if you want to call your custom Python code?  Well the Python interpreter current working directory is the current MATLAB directory:\n   <\/p>\n
cwd = py.os.getcwd<\/pre>\n
cwd = \r\n  Python str with no properties.\r\n\r\n    C:\\Documents\\MATLAB\\potw\\PyAddPath\r\n<\/pre>\n
So if your code lives here, you’re all set.  However, you may (probably!) have your Python code somewhere else.  So this is where this week’s submission comes in.  You can use py_addpath<\/tt> to add another directory to the Python interpreter’s path.  Optionally, it can also add the directory to the MATLAB path.\n   <\/p>\n
Personally, I’m no longer modifying the MATLAB path myself and using (and recommending!) Projects<\/a> for anything where path or other setup needs to be configured. Because Projects afford us a “Run at Startup” option, I can have it run MATLAB code that takes care of the Python path as well using Eric’s py_addpath<\/tt>.\n   <\/p>\n
Let’s take a look at an example. NOTE:<\/b> Everything we’re doing with Python here could also be done with MATLAB’s webread<\/tt><\/a> but we’ll pretend we’re obligated to use this Python function.\n   <\/p>\n
Here’s the Python function:<\/p>\n
\r\n\"\"\"\r\ndataLib.py imports 1-minute bars from GDAX \r\nbuilt with Python 3.5 on 4\/3\/2018\r\n\r\nExample: getPriceData('ETH', '2018-03-16T17:41:26Z', '2018-03-16T18:14:46Z')\r\n\r\nTo call from Python:\r\n>>import dataLib\r\n>>dataLib.getPriceData('ETH', '2018-03-16T17:41:26Z', '2018-03-16T18:14:46Z')\r\n\r\n\"\"\"\r\n\r\ndef getPriceData(product, start, stop):\r\n\timport urllib.request\r\n\timport json\r\n\r\n\t# all cryptocurrency products returned in USD\r\n\tproduct = product + '-USD'\r\n\t\r\n\t# granularity is in seconds, so we are getting 1-minute bars\r\n\tgranularity = '60'\r\n\r\n\t# returns back: [time, low, high, open, close, volume]\r\n\turl = 'https:\/\/api.pro.coinbase.com\/products\/' + product + '\/candles?start=' + start + '&end=' + stop + '&granularity=' + granularity\r\n\r\n\t# execute call to the website\r\n\turlRequest = urllib.request.Request(url, data=None, headers={'User-Agent': 'Mozilla\/5.0 (Macintosh; Intel Mac OS X 10_9_3) AppleWebKit\/537.36 (KHTML, like Gecko) Chrome\/35.0.1916.47 Safari\/537.36'})\r\n\tresponse = urllib.request.urlopen(urlRequest)\r\n\thtml = response.read()\r\n\r\n\t# python 3.x requires decoding from bytes to string \r\n\tjsonData = json.loads(html.decode())\r\n\treturn jsonData\r\n\r\n###########################################################################################\t\r\n\t\r\ndef parseJson(json_data):\r\n\tfrom array import array\r\n\r\n\t# return back time and close data\r\n\tdates = [row[0] for row in json_data]\r\n\tdata = [row[4] for row in json_data]\r\n\r\n\t# convert to 1D array \r\n\tdateArray = array('d')\r\n\tdataArray = array('d')\r\n\tdateArray.fromlist(dates)\r\n\tdataArray.fromlist(data)\r\n\t\r\n\t# wrap both time series in a dictionary\r\n\tcloseTimeSeries = {'Date': dateArray, 'Close': dataArray}\r\n\treturn closeTimeSeries\r\n<\/pre>\n
And here’s the function I would add to the project startup to add the Python folder at project startup.<\/p>\n
\r\nfunction<\/span> addPythonDataLib()\r\nprj = currentProject;\r\npy_addpath(fullfile(prj.RootFolder, 'Python'<\/span>));\r\nend<\/span>\r\n\r\n<\/pre>\n
Now after opening the project, we can use the dataLib.py<\/tt> functionality.\n   <\/p>\n
% Query for Ethereum prices<\/span>\r\nstartDate = '2018-03-16T12:00:00Z'<\/span>;\r\nstopDate = '2018-03-16T17:00:00Z'<\/span>;\r\njsonData = py.dataLib.getPriceData('ETH'<\/span>, startDate, stopDate);\r\ndata = py.dataLib.parseJson(jsonData);\r\n\r\n% Convert to MATLAB Data Types<\/span>\r\ndata = struct(data);\r\ndata.Date = double(data.Date)';\r\ndata.Date = datetime(data.Date, 'ConvertFrom'<\/span>, 'posixtime'<\/span>, 'TimeZone'<\/span>, 'America\/New_York'<\/span>);\r\ndata.Close = double(data.Close)';\r\ndata = table2timetable(struct2table(data));\r\ndisp(head(data))\r\nstackedplot(data);<\/pre>\n
            Date            Close \r\n    ____________________    ______\r\n    16-Mar-2018 13:00:00     621.1\r\n    16-Mar-2018 12:59:00     621.1\r\n    16-Mar-2018 12:58:00     621.1\r\n    16-Mar-2018 12:57:00    621.09\r\n    16-Mar-2018 12:56:00    621.09\r\n    16-Mar-2018 12:55:00    621.09\r\n    16-Mar-2018 12:54:00    621.06\r\n    16-Mar-2018 12:53:00    621.87\r\n<\/pre>\n
 <\/p>\n
One suggestion for Eric, is that the function could use convertStringsToChars<\/tt><\/a> to allow for MATLAB string inputs to be passed in as well without needing to change any algorithmic parts.  I.e.\n   <\/p>\n
directory = convertStringsToChars(directory);<\/pre>\n
Comments<\/a><\/h3>\n
Give it a try and let us know what you think here<\/a> or leave a comment<\/a> for Eric.\n   <\/p>\n