Python is a popular language used for web development

https://developers.google.com/edu/python

1. build python
   ./configure
   make
   make install

2. install gunicorn
   pip3 install gunicorn

3. in apache enable proxy modules
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so

4. add ProxyPass entry in vhost
ProxyPass "/pybase/" "http://127.0.0.1:8000/"

5. configure gunicorn.service file in  /usr/lib/systemd/system/gunicorn.service

===== Start gunicorn.service File ======
[Unit]
Description=The Apache HTTP Server
After=network.target

[Service]
MAINPID = /run/cmdb/cmdb.pid
WorkingDirectory = /m/member/pybase
ExecStartPre = /bin/mkdir /run/cmdb
ExecStart=/usr/local/bin/gunicorn --workers=4 myapp:app --chdir="/m/member/pybase" --pid /run/cmdb/cmdb.pid
ExecReload=/bin/kill -s HUP $MAINPID
ExecStop=/bin/kill -s HUP $MAINPID
ExecStopPost = /bin/rm -rf /run/cmdb

PrivateTmp=true

[Install]
WantedBy=multi-user.target

===== End gunicorn.service File ======

A) definition of a function
  def funcname(arg1,arg2):

B) spacing matters - indentation defines block

C) definition of if statement
  if (a == 1):
     a += 1;

D) for statement
   for (x in environ):
       data += x+environ[x];

E) Templates
   Jinja2 is the most prevalent template engine
   sample code to load from file:

   import jinja2
   def display_template():
      templateLoader = jinja2.FileSystemLoader(searchpath="./templates")
      templateEnv = jinja2.Environment(loader=templateLoader)
      templateFile = "template.html"
      template = templateEnv.get_template(templateFile)
      return template.render();

F) getting data from the database
   - basic level method (cursor)
   ---------------------------------
   import mysql.connector
   def get_data(sql):
     cnx = mysql.connector.connect(
         user='membermaster',
         password='XXXXX',
         host='127.0.0.1',
         database='mainmemberdb')

    data = "<table>\n"
    if cnx and cnx.is_connected():
       with cnx.cursor() as cursor:
          result = cursor.execute(sql)
          rows = cursor.fetchall()
          for row in rows:
              data += "<tr>\n"
              for col in row:
                  data += "   <td>"+col+"</td>\n"
              data += "</tr>\n"
    data += "</table>\n\n"
    cnx.close()
    return data
   ---- end code --------
   -More sophisticated is to use pandas to load the data to a grid
   pandas can output the data in a number of formats
   pandas is a library that allows data to be loaded into a grid
   that can then be displayed.
--------------------------------------------------------------
def get_table(sql):
   try:
       cnx = mysql.connector.connect(
           user='membermaster',
           password='XXXXX',
           host='127.0.0.1',
           database='mainmemberdb')
       results = pd.read_sql(sql,cnx)
       cnx.close()
       # html table has systables as a css class systables in addition to
       # dataframe... e.g. <table class='dataframes systables'>
       return results.to_html( classes= "systables")
   except Exception as e:
    cnx.close()
    return str(e)
---- end code -----

G) Get an argument from command line
   import sys
   def main():
      if (len(sys.argv)>=2:
          print("ARG 1:",sys.argv[1]);

    if __name__ == '__main__':
       main()

H) repeat string... * syntax
   print("foo"*3);
   >>foofoofoo

I) From the command line - help(keyword)
   help(len)

J)To convert numbers to strings
    mystring = str(10);

K) numbers:
   1. no ++ - can't do a++
   2. integer division is two // e.g. 2.4 // 2 = 1

L) raw strings
   raw= r'this\t\n and that'
   multi= """ hello
      world """

M) slices
   s="hello";
   something = s[1:4]
   >>> 'ell'
   s[-1]
   >> 'o'
N) strings
   [f strings]
    value = 2.791514
    print(f'approximate value = {value:.2f}')

O) if statements
    if a==b:
        print("a equals b")
    elif c==d
        print("c equals d")
    else
        print("magic")

P) and/or  ( there is no && or || )
   if a and b:
      print(true)
   if a or b
      print(false)

Q) for/in
   for key in list:
     iterate here
   if "moe" in list:
       do if moe is in list
       

R) dict
   mydict = {key1:value1,key2:value2}
   mydict = {}
   usage: myvar = mydict[key1];
   mykeys = mydict.keys();
   myvalues = mydict.values();
   myitems = mydict.items();  // tuple
   for k,v in myitems : print (k,"=",v)
   s = : %(word)s %mydict
   del mydict[0];
   del mydict[-2:0]

S) files
   #open file
   f = fopen("filaneme.txt", "rt", encoding='utf-8')
   for line in f:
       print (line, end='')
   f.close();       

T) regular expressions
   import re
   mystr = " hello 123 456";
   mymatch = re.search(mystr, '\d+');
   mymatch = re.findall(mystr, "\d+");
   mymatch = re.sub(mystr, "123", "\d+");

U) major important libraries
   os lib: os.listdir(dir), os.path.join(dir,filename), os.path.abspath(filename), os.path.dirname(filename)
          os.path.basename(filename), os.path.exists(filename), os.mkdir(path), os.mkdirs(path1)
   shutil lib: shutil.copy(source,target)
   subprocess:
       output = subprocess.check_output(cmd, stderr=subprocess.STDOUT) -
       subprocess.popen
       subprocess.call
   urilib lib:
      ufile = urllib.request.urlopen(url);
      text = ufile.read()
      info = ufile.info()
      baseurl = ufile.geturl()
      urllib.request.urlretrieve(url, filename)
      urllib.parse.urljoin(baseurl, url)
      from urllib.request import urlopen
   uriparse lib: