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Python Objects

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I promised to give my students a full example of how to write and execute a Python object. There were two motivations for this post. The first was driven by my students trying to understand the basics and the second my somebody else saying Python couldn’t deliver objects. Hopefully, this code is simple enough for both audiences. I gave them this other tutorial on writing and mimicking overloaded Python functions earlier.

This defines a Ball object type and a FilledBall object subtype of Ball. It incorporates the following elements:

  • A special __init__ function, which is a C/C++ equivalent to a constructor.
  • A special __str__ function represents a class object instance as a string. It is like the getString() equivalent in the Java programming language.
  • A bounce instance function, which means it acts on any instance of the Ball object type or FilledBall object subtype.
  • A get_direction instance function and it calls the __format local object function, which is intended to mimic a private function call, like other object-oriented programming languages.
  • A private name __format function (Private name mangling: When an identifier that textually occurs in a class definition begins with two or more underscore characters and does not end in two or more underscores, it is considered a private name of that class.)

You can test this code by creating the $PYTHONPATH (Unix or Linux) or %PYTHONPATH% (Windows) as follows with all the code inside the present working directory, like this in Unix or Linux:

export set $PYTHONPATH=.

Then, you create the Ball.py file with this syntax:

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# Creates a Ball object type and FilledBall object subtype.
class Ball:
  # User-defined constructor with required parameters.
  def __init__(self, color = None, radius = None, direction = None):
    # Assign a default color value when the parameter is null.
    if color is None:
      self.color = "Blue"
    else:
      self.color = color.lower()
 
    # Assign a default radius value when the parameter is null.
    if radius is None:
      self.radius = 1
    else:
      self.radius = radius
 
    # Assign a default direction value when the parameter is null.
    if direction is None:
      self.direction = "down"
    else:
      self.direction = direction.lower()
 
    # Set direction switch values.
    self.directions = ("down","up")
 
  # User-defined standard function when printing an object type.
  def __str__(self):
    # Build a default descriptive message of the object.
    msg = "It's a " + self.color + " " + str(self.radius) + '"' + " ball"
 
    # Return the message variable.
    return msg
 
  # Define a bounce function.
  def bounce(self, direction = None):
    # Set direction on bounce.
    if not direction is None:
      self.direction = direction
    else:
      # Switch directions.
      if self.directions[0] == self.direction:
        self.direction = self.directions[1]
      elif self.directions[1] == self.direction:
        self.direction = self.directions[0]
 
  # Define a bounce function.
  def getDirection(self):
    # Return current direction of ball.
    return self.__format(self.direction)
 
  # User-defined pseudo-private function, which is available
  # to instances of the Ball object and any of its subtypes.
  def __format(self, msg):
    return "[" + msg + "]"
 
# This is the object subtype, which takes the parent class as an
# argument.
class FilledBall(Ball):
  def __init__(self, filler = None):
    # Instantiate the parent class and then any incremental 
    # parameter values.
    Ball.__init__(self,"Red",2)
 
    # Add a default value or the constructor filler value.
    if filler is None:
      self.filler = "Air".lower()
    else:
      self.filler = filler
 
  # User-defined standard function when printing an object type, which 
  # uses generalized invocation.
  def __str__(self):
    # Build a default descriptive message of the object.
    msg = Ball.__str__(self) + str(" filled with " + self.filler)
 
    # Return the message variable.
    return msg

Next, let’s test instantiating the Ball object type with the following code:

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#!/usr/bin/python
 
# Import the Ball class into its own namespace.
import Ball
 
# Assign an instantiated class to a local variable.
myBall = Ball.Ball()
 
# Check whether the local variable holds a valid Ball instance.
if not myBall is None:
  print(myBall, "instance.")
else:
  print("No Ball instance.")
 
# Loop through 10 times changing bounce direction.
for i in range(1,10):
  # Find dirction of ball.
  print(myBall.getDirection())
 
  # Bounce the ball.
  myBall.bounce()

Next, let’s test instantiating the FilledBall object subtype with the following code:

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#!/usr/bin/python
 
# Import the Ball class into its own namespace.
import Ball
 
# Assign an instantiated class to a local variable.
myBall = Ball.FilledBall()
 
# Check whether the local variable holds a valid FilledBall instance.
if not myBall is None:
  print(myBall, "instance.")
else:
  print("No Ball instance.")
 
# Loop through 10 times changing bounce direction.
for i in range(1,10):
  # Find dirction of ball.
  print(myBall.getDirection())
 
  # Bounce the ball.
  myBall.bounce()

As always, I hope this helps those looking to learn and extend their knowledge.

Written by maclochlainn

June 25th, 2023 at 2:07 pm

Posted in Python,Python 3.x,Uncategorized

Tagged with

MySQL Posts Summary

without comments

Here’s a quick catalog for my students of PowerShell, JavaScript, and Python examples connecting to MySQL:

As always, I hope this helps those looking for a code sample.

Written by maclochlainn

June 16th, 2023 at 12:38 am

Posted in JavaScript,Linux,MySQL,MySQL 8,PowerShell,Python 3.x

Tagged with ,

Python Functions

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It seems a number of my students had some confusion over how to write overloaded Python functions. So, I prepared this little tutorial using Python 3.

The first basic1.py example file is a standalone Python file that:

  • Defines a hello() world function.
  • Calls the local hello() world function.
#!/usr/bin/python
 
# Define a hello() function.
def hello():
  print("Hello World!")
 
# Call the hello() function.
hello()

You can test the basic1.py script as follows:

./basic1.py

It prints:

Hello World!

The second basic2.py example file is also a standalone Python file that:

  • Attempts to define overloaded hello() world functions. One version takes no arguments and the other takes one argument.
  • Attempts to call the overloaded local hello() world function without any arguments and with one argument.
#!/usr/bin/python
 
# Call the hello() function without any arguments.
def hello():
  print("Hello World!")
 
# Call the hello() function with one argument.
def hello(whom):
  print("Hello", whom)
 
# Call the overloaded hello() functions.
hello()
hello("Henry")

You can test the basic2.py script as follows:

./basic2.py

It successfully defines the hello() function and then it replaces it with the hello(whom) function. So, it raises the following runtime error because the call to the hello() world function finds the hello(whom) function and the call lacks a call parameter.

Traceback (most recent call last):
  File "/home/student/Code/python/funct/./basic2.py", line 12, in <module>
    hello()
TypeError: hello() missing 1 required positional argument: 'whom'

The third basic3.py example file is also a standalone Python file that:

  • Defines a function that acts like an overloaded hello(whom=None) world function.
  • Call the local hello(whom=None) world function without any arguments and with one argument. It works because you do two things:
    • You assign a default null value to the whom parameter, which makes the parameter optional in the function’s signature.
    • You use an if-statement to manage the behavior of a null parameter. The None keyword defines a null value. Please note that the is reference comparison operator is necessary to evaluate whether a variable contains a null value.
#!/usr/bin/python
 
# Call the hello() function with an optional parameter; and
# manage the inner workings with and without a parameter.
def hello(whom = None):
  if whom is None:
    print("Hello World!")
  else:
    print("Hello", whom + "!")
 
# Call the overloaded hello() functions.
hello()
hello("Henry")

You can test the basic3.py script as follows:

./basic3.py

It prints:

Hello World!
Hello Henry!

At this point, we need to qualify how you can position a Python library file in a development directory. Development directories aren’t typically in the standard library locations, which means you need to define the directories in the $PYTHONPATH environment variable.

There’s a convenient trick that lets you set the $PYTHONPATH value so that you can use it across multiple test environments. It requires you to create an src directory for your library source code inside the directory where you develop code that will use library functions.

After creating the src directory, you can set the $PYTHONPATH environment variable with a relative src directory in the following syntax:

export set PYTHONPATH=$PYTHONPATH:./src:.

It will now let Python look for libraries in the src subdirectory or the present working directory.

Next, you deploy the following hello(whom=None) function in a lib.py file inside the src subdirectory.

# Call the hello() function with an optional parameter; and
# manage the inner workings with and without a parameter.
def hello(whom = None):
  if whom is None:
    print("Hello World!")
  else:
    print("Hello", whom + "!")

In the parent directory of the src subdirectory create the basic4.py file, like:

#!/usr/bin/python
 
# Import the lib.py file as a lib package.
import lib
 
# Call the hello() function without arguments and
# with one argument within the namespace of the lib 
# library.
lib.hello()
lib.hello("Henry")

An alternate way to write the basic4.py program imports a single namespace element (like a variable, function, or object) and places it in the local namespace of the program. You can redefine hello() function

#!/usr/bin/python
 
# Define the hello namespace element from the lib 
# library in the current program.
from lib import hello
 
# Call the hello() function without arguments and
# with one argument within the namespace of the lib
# library.
hello()
hello("Henry")

The hello() function only prints messages. You can add a return statement to return a value from the hello() function. The modified library returns a string rather than printing a string, as follows:

# Call the hello() function with an optional parameter; and
# manage the inner workings with and without a parameter.
def hello(whom = None):
  if whom is None:
    return "Hello World!"
  else:
    return "Hello " + whom + "!"
 
# Call the goodbye() function with an optional parameter; and
# manage the inner workings with and without a parameter.
def goodbye(whom = None):
  if whom is None:
    return "Goodbye World!"
  else:
    return "Goodbye " + whom + "!"

You would then make the following changes to the basic5.py program that calls the lib.py library file. You could also call the goodbye() function inside the imported lib scope. However, you wouldn’t be able to call the goodbye() function if you had imported only the hello() function from the lib package into the local namespace.

#!/usr/bin/python
 
# Import the lib.py file as a lib package.
import lib
 
# Call the hello() function without arguments and
# with one argument within the namespace of the lib
# library.
print(lib.hello())
print(lib.hello("Henry"))

As always, I hope this helps those looking to understand and use functions in Python.

Written by maclochlainn

June 1st, 2023 at 11:08 pm

Posted in Python,Python 3.x

Tagged with

AlmaLinux Flask

with one comment

This post shows how to install and test Flask with Python on AlmaLinux. You install the flask Python libraries with the following commands as the student user. The student user is in the sudoer group.

pip3 install flask_sslify --user student

It produces the following log file:

Display detailed console log →

Collecting flask
  Downloading Flask-2.2.2-py3-none-any.whl (101 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 101.5/101.5 kB 737.3 kB/s eta 0:00:00
Collecting student
  Downloading Student-0.0.1-py3-none-any.whl (2.5 kB)
Collecting itsdangerous>=2.0
  Downloading itsdangerous-2.1.2-py3-none-any.whl (15 kB)
Collecting importlib-metadata>=3.6.0
  Downloading importlib_metadata-5.2.0-py3-none-any.whl (21 kB)
Collecting Jinja2>=3.0
  Downloading Jinja2-3.1.2-py3-none-any.whl (133 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 133.1/133.1 kB 1.9 MB/s eta 0:00:00
Collecting Werkzeug>=2.2.2
  Downloading Werkzeug-2.2.2-py3-none-any.whl (232 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 232.7/232.7 kB 18.5 MB/s eta 0:00:00
Collecting click>=8.0
  Downloading click-8.1.3-py3-none-any.whl (96 kB)
     ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 96.6/96.6 kB 16.2 MB/s eta 0:00:00
Collecting zipp>=0.5
  Downloading zipp-3.11.0-py3-none-any.whl (6.6 kB)
Collecting MarkupSafe>=2.0
  Downloading MarkupSafe-2.1.1-cp39-cp39-manylinux_2_17_x86_64.manylinux2014_x86_64.whl (25 kB)
Installing collected packages: zipp, student, MarkupSafe, itsdangerous, click, Werkzeug, Jinja2, importlib-metadata, flask
Successfully installed Jinja2-3.1.2 MarkupSafe-2.1.1 Werkzeug-2.2.2 click-8.1.3 flask-2.2.2 importlib-metadata-5.2.0 itsdangerous-2.1.2 student-0.0.1 zipp-3.11.0

You can use the following hello.py test program

# Import libraries.
from flask import Flask, escape, request
from markupsafe import escape
 
# Define the application.
app = Flask(__name__)
 
# Define a base URI route and function.
@app.route('/')
def index():
  return "Hello World!"
 
# Define an application URI route and function.
@app.route("/hello")
def hello():
  name = request.args.get("name","Simon")
  return f'Hello {escape(name)}!'
 
# Define an about URI route and function.
@app.route("/about")
def about():
  return "About Page."
 
# Define an <username> variable rule for a route.
@app.route("/user/<string:username>")
def show_user_profile(username):
  return 'User [%s].' % escape(username)
 
# Define an <username> variable rule for a route.
@app.route("/year/<int:year>")
def show_post(year):
  return 'Year [%d].' % year
 
# Run the file.
if __name__ == "__main__":
  app.run()

You can start the Flask server with the following two commands in a separate shell session. This allows you to monitor activities and writes an activity log:

export FLASK_APP=hello.py
flask run

It also writes a compiled version of the hello.py program to the __pycache__ directory. If you make changes to the base file, you must delete the cached version in the __pycache__ directory.

You can test it by typing any of the following URL in a browser:

  1. The index page without a routing label in the URL: 

    http://localhost:5000/hello

    It’ll print the following:

    Hello World!
  2. The index page with a hello routing label in the URL: 

    http://localhost:5000/hello

    It’ll print the following:

    Hello Simon!
  3. The index page with a about routing label in the URL: 

    http://localhost:5000/about

    It’ll print the following:

    About Page.
  4. The index page with a user routing label in the URL: 

    http://localhost:5000/user/Somebody

    It’ll print the following:

    User [Somebody].
  5. The index page with a year routing label in the URL: 

    http://localhost:5000/year/1986

    It’ll print the following:

    Year [1986].

The activity log shows the following:

 * Serving Flask app 'hello.py'
 * Debug mode: off
WARNING: This is a development server. Do not use it in a production deployment. Use a production WSGI server instead.
 * Running on http://127.0.0.1:5000
Press CTRL+C to quit
127.0.0.1 - - [29/Dec/2022 19:33:12] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [29/Dec/2022 19:33:21] "GET /hello HTTP/1.1" 200 -
127.0.0.1 - - [29/Dec/2022 19:33:27] "GET /about HTTP/1.1" 200 -
127.0.0.1 - - [29/Dec/2022 19:33:48] "GET /year/1986 HTTP/1.1" 200 -
127.0.0.1 - - [29/Dec/2022 19:34:09] "GET /user/Somebody HTTP/1.1" 200 -

If you stop the process with the Ctrl+Z, the process will not stop but not the listener process. As a sudoer user, you can find the open listener process with the following command:

sudo netstat -nlp | grep 5000
[sudo] password for student:

It will return something like this:

tcp        0      0 127.0.0.1:5000          0.0.0.0:*               LISTEN      143363/python3

You kill the process without prejudice by using the following command:

kill -9 143363

As always, I hope this helps those who are looking for step-by-step instructions.

Written by maclochlainn

December 29th, 2022 at 4:35 pm

Posted in flask,Python,Python 3.x

AlmaLinux Install & Configuration

without comments

This is a collection of blog posts for installing and configuring AlmaLinux with the Oracle, PostgreSQL, MySQL databases and several programming languages. Sample programs show how to connect PHP and Python to the MySQL database.

I used Oracle Database 11g XE in this instance to keep the footprint as small as possible. It required a few tricks and discovering the missing library that caused folks grief eleven years ago. I build another with a current Oracle Database XE after the new year.

If you see something that I missed or you’d like me to add, let me know. As time allows, I’ll try to do that. Naturally, the post will get updates as things are added later.

Written by maclochlainn

December 21st, 2022 at 5:29 pm

Posted in AlmaLinux,Apache,Database,DBA,Java,Java 17,LAMP,Linux,MySQL,MySQL 8,MySQL Connect/J,Oracle,Oracle 11g,Oracle DBA,Oracle Developer,Oracle XE,pdo,Perl,Perl DBI,pgAdmin4,PHP,Postgres,PostgreSQL,PostgreSQL 15,Python 3.x,Rust,VMWare,VSCode

Tagged with , , , , , , , ,

AlmaLinux MySQL+Python

without comments

After installing and configuring MySQL 8.0.30, I installed the Python connector. During that process on AlmaLinux, there were several changes since I last installed the Python’s mysql module. Here are the step-by-step instructions after installing and configuring MySQL Server (blog for those steps).

Using the MySQL Connector/Python X DevAPI Reference, you must install the pip utility before you install the library. You install the pip library as a sudoer user with the following command:

sudo yum install -y pip

Then, using the pip utility as a sudoer user install the mysql-connector-python module with the following command:

sudo pip install mysql-connector-python

Please note that this type of library installation can cause problems when you maintain multiple testing environments. If you plan to maintain multiple testing environments, please install this library in a virtual environment.

You create a bare-bones Python connection test program, like connect.py below:

# Import the library.
import mysql.connector
from mysql.connector import errorcode
 
try:
  # Open connection.
  cnx = mysql.connector.connect(user='student',
                                password='student',
                                host='127.0.0.1',
                                database='studentdb')
 
  # Print the value.
  print("Database connection resolved.")
 
# Handle exception and close connection.
except mysql.connector.Error as e:
  if e.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
  elif e.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
  else:
    print(e)
 
# Close the connection when the try block completes.
else:
  cnx.close()

You test the connect.py program with this command:

python connect.py

It’ll return the following provided you provisioned the student user and studentdb database:

Database connection resolved.

If you’d like to run it without calling the python executable, you can add the following as the first line:

#/usr/bin/python

and, change the default file permissions from

-rw-rw-r--. 1 student student 717 Oct 30 13:57 connect.py

with the chmod command to

-rwxr-xr-x. 1 student student 717 Oct 30 13:57 connect.py

These instructions should set you up to develop Python code against your AlmaLinux MySQL studentdb database. You use this syntax, assuming a default $PATH environment variable that excludes the present working directory.

./connect.py

As always, I hope this helps those trying to get a complete solution.

Written by maclochlainn

October 30th, 2022 at 12:37 pm

Posted in AlmaLinux,Linux,MySQL,MySQL 8,pip,Python,Python 3.x

Tagged with , , ,

Quick Python Bit #1

without comments

A student asked for a Python example that would find a string starting with a vowel and prepend an “An” or starting with a non-vowel and prepend an “A”. As a rule, this one seems to make sense to most beginning programmers.

#/usr/bin/python
 
# Import the regular expression library.
import re
 
# Create a list of words to check.
haystack = ['anything','something','nothing']
 
# Create a regular expression for a leading vowel.
needle = "^[AEIOUaeiou].*$"
 
# Read through the haystacks and use the right article. 
for i in range(0,len(haystack),1):
  if re.search(needle,haystack[i],re.IGNORECASE):
    print("An",haystack[i]+".")
  else:
    print("A",haystack[i]+".")

However, this loop is much cleaner:

#/usr/bin/python
 
# Import the regular expression library.
import re
 
# Create a list of words to check.
haystack = ['anything','something','nothing']
 
# Create a regular expression for a leading vowel.
needle = "^[AEIOUaeiou].*$"
 
# Read through the haystacks and use the right article. 
for i in haystack:
  if re.search(needle,i,re.IGNORECASE):
    print("An",i+".")
  else:
    print("A",i+".")

Both programs print the following:

An anything.
A something.
A nothing.

As always, happy to help write another example.

Written by maclochlainn

October 26th, 2022 at 11:32 pm

Posted in Python,Python 3.x

Tagged with

MySQL JSON Tricks

without comments

Are they really tricks or simply basic techniques combined to create a solution. Before writing these mechanics for using native MySQL to create a compound JSON object, let me point out that the easiest way to get one is to use the MySQL Node.js library, as shown recently in my “Is SQL Programming” blog post.

Moving data from a relational model output to a JSON structure isn’t as simple as a delimited list of columns in a SQL query. Let’s look at it in stages based on the MySQL Server 12.18.2 Functions that create JSON values.

Here’s how you return single row as a JSON object, which is quite straightforward:

SELECT JSON_OBJECT('first_name',c.first_name,'last_name',c.last_name) AS json_result
FROM   contact c
WHERE  first_name = 'Harry'
AND    last_name = 'Potter';

It returns:

+------------------------------------------------+
| json_result                                         |
+------------------------------------------------+
| {"last_name": "Potter", "first_name": "Harry"} |
+------------------------------------------------+
1 row in set (0.00 sec)

With a GROUP_CONCAT function, let’s capture a JSON array of all three Potter family members:

SELECT CONCAT('['
             , GROUP_CONCAT(
                 JSON_OBJECT('first_name',first_name
                            ,'last_name',last_name ) SEPARATOR ',')
             ,']') AS json_result 
FROM   contact c
WHERE  c.last_name = 'Potter';

It returns an array of JSON objects:

+-----------------------------------------------------------------------------------------------------------------------------------------------+
| [{"last_name": "Potter", "first_name": "Harry"},{"last_name": "Potter", "first_name": "Ginny"},{"last_name": "Potter", "first_name": "Lily"}] |
+-----------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

Next, let’s put a 1:many relationship between the member and contact table into a JSON structure with a single account number and an array of contact. It requires a second call to the JSON_OBJECT function and the addition of a GROUP BY clause in the query.

SELECT   JSON_OBJECT(
            'account_number', account_number
           ,'contact', CONCAT('['
                         , GROUP_CONCAT(
                              JSON_OBJECT('first_name',first_name
                             ,'last_name',last_name ) SEPARATOR ',')
                             ,']')
         ) AS json_result 
FROM     member m INNER JOIN contact c
ON       m.member_id = c.member_id
WHERE    c.last_name = 'Potter'
GROUP BY m.account_number;

It returns the following string with an annoying set of backslashes. It also inverts the column order, which appears unavoidable but it shouldn’t matter because the order of name-value pairs in JSON is immaterial.

+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| {"contact": "[{\"last_name\": \"Potter\", \"first_name\": \"Harry\"},{\"last_name\": \"Potter\", \"first_name\": \"Ginny\"},{\"last_name\": \"Potter\", \"first_name\": \"Lily\"}]", "account_number": "US00011"} |
+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

The following quick little Python code cleans up the JSON string by removing the backslashes and extraneous quotes around the array of contacts.

# Import the library.
import mysql.connector
from mysql.connector import errorcode
 
try:
  # Open connection.
  cnx = mysql.connector.connect(user='student', password='student',
                                host='127.0.0.1',
                                database='studentdb')
  # Create cursor.
  cursor = cnx.cursor()
 
  # Set the query statement.
  query = ("SELECT JSON_OBJECT( "
           "'account_number', m.account_number "
           ",'contact', CONCAT('[' "
           "              , GROUP_CONCAT( "
           "                   JSON_OBJECT('first_name', c.first_name "
           "                  ,'last_name', c.last_name ) SEPARATOR ',') "
           "                  ,']')) AS json_result "
           "FROM   contact c INNER JOIN member m "
           "ON     c.member_id = m.member_id "
           "WHERE  c.last_name = %s "
           "GROUP BY account_number")
 
  # Execute cursor.
  cursor.execute(query,["Potter"])
 
  # Display the column returned by the query stripped of backslashes and
  # extraneous quotes.
  for (row) in cursor:
    for column in range(len(row)):
      print(row[column].replace("\\","").replace("\"[","[").replace("]\"","]"))
 
  # Close cursor.
  cursor.close()
 
# ------------------------------------------------------------
# Handle exception and close connection.
except mysql.connector.Error as e:
  if e.errno == errorcode.ER_ACCESS_DENIED_ERROR:
    print("Something is wrong with your user name or password")
  elif e.errno == errorcode.ER_BAD_DB_ERROR:
    print("Database does not exist")
  else:
    print("Error code:", e.errno)        # error number
    print("SQLSTATE value:", e.sqlstate) # SQLSTATE value
    print("Error message:", e.msg)       # error message
 
# Close the connection when the try block completes.
else:
  cnx.close()

It returns:

{"contact": [{"last_name": "Potter", "first_name": "Harry"},{"last_name": "Potter", "first_name": "Ginny"},{"last_name": "Potter", "first_name": "Lily"}], "account_number": "US00011"}

I hope this helps exhibit less well known MySQL syntax. Check this post to see how to insert a result set without Python as an intermediary.

Written by maclochlainn

June 23rd, 2022 at 12:46 am

Posted in JSON,MySQL,MySQL 8,Python,Python 3.x,sql

Tagged with , ,

Fedora for macOS ARM64

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I’m always updating VMs, and I was gratified to notice that there’s a Fedora arm64 ISO. If you’re interested in it, you can download the Live Workstation from here or the Fedora Server from here.

Unfortunately, I only have macOS running on i7 and i9 Intel Processors. It would be great to hear back how it goes for somebody one of the new Apple M1 chip.

I typically install the workstation version because it meets my needs to run MySQL and other native Linux development tools. However, the server version is also available. Fedora is a wonderful option, as a small footprint for testing things on my MacBookPro.

Written by maclochlainn

May 7th, 2022 at 1:34 pm

Posted in Fedora,Linux,macOS,MySQL,MySQL 8,Python 3.x

Tagged with , ,

Install Python on Windows

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A number of my students want to run the databases and development environments on Windows rather than Linux. Some of the students have various problems configuring a virtual machine or Docker environment on their laptops.

Installing Python on Windows is quite straightforward. You simply open a Windows Command Line Interface (CLI) with Administrator privileges and type python at the command line. It will launch a dialog that lets you download and install Python.

After the installation, you are returned to the Windows CLI where you can type python to launch the Python IDE. You’ll learn that it’s an older version when it opens.

Python 3.10.2 (tags/v3.10.2:a58ebcc, Jan 17 2022, 14:12:15) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>

After installing Python, I started to install drivers with the Python package-management utility – PIP. I loaded the psycopg2 driver first and discovered that Windows installed an older version of PIP, as qualified when I installed the Python library:

pip install psycopg2
Collecting psycopg2
  Downloading psycopg2-2.9.3-cp310-cp310-win_amd64.whl (1.2 MB)
     |████████████████████████████████| 1.2 MB 1.6 MB/s
Installing collected packages: psycopg2
Successfully installed psycopg2-2.9.3
WARNING: You are using pip version 21.2.4; however, version 22.0.3 is available.
You should consider upgrading via the 'C:\Users\mclaughlinm\AppData\Local\Microsoft\WindowsApps\PythonSoftwareFoundation.Python.3.10_qbz5n2kfra8p0\python.exe -m pip install --upgrade pip' command.

So, I immediately installed the new version of PIP and discovered that I have to manually reset the %PATH% environment variable.

python -m pip install --upgrade pip
Requirement already satisfied: pip in c:\program files\windowsapps\pythonsoftwarefoundation.python.3.10_3.10.752.0_x64__qbz5n2kfra8p0\lib\site-packages (21.2.4)
Collecting pip
  Downloading pip-22.0.3-py3-none-any.whl (2.1 MB)
     |████████████████████████████████| 2.1 MB 656 kB/s
Installing collected packages: pip
  WARNING: The scripts pip.exe, pip3.10.exe and pip3.exe are installed in 'C:\Users\mclaughlinm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.10_qbz5n2kfra8p0\LocalCache\local-packages\Python310\Scripts' which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.
Successfully installed pip-22.0.3

The default location for the PIP.exe and PIP3.exe are found in the:

C:\Users\mclaughlinm\AppData\Local\Microsoft\WindowsApps

Rather than put the newer directory in the System Environment %PATH% variable, I created a batch file that lets me set it only when I need it.

SET PATH=C:\Users\mclaughlinm\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.10_qbz5n2kfra8p0\LocalCache\local-packages\Python310\Scripts;%PATH%

After installing the psycopg2 driver, I tested the new_hire.sql and new_hire.py files from this earlier Linux post successfully. I hope this helps those looking to work with Python on Windows.

Written by maclochlainn

March 2nd, 2022 at 11:48 pm

Posted in PostgreSQL,PostgreSQL 14,Python,Python 3.x,Windows 10

Tagged with

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