A place to keep and find your hints on Python use.

Possible Links for Training and Reference

• https://automationstepbystep.com/ (Selenium Reference)
  • python – m pip install selenium
• https://codemy.com/ (multiple courses)
• https://www.w3schools.com/ (tutorials)
• Good information from John Elder at < https://tkinter.com/ >
• realpython.com/python-gui-tkinter
• https://realpython.com/python-virtual-environments-a-primer/
• Site to enter code directly in browser: http://replit.com
• Site with instructions on installing and using opencv: https://www.pyimagesearch.com/
• Site with videos on using python with Excel and Word: https://pythonandvba.com/
• Anvil Works, a site for creating GUI applications with Python: https://anvil.works/ or anvil.works/pythonsimplified
  • On line tutorial: https://www.youtube.com/watch?v=NiQdsK3H57Y
• Link to good instructions on how to upgrade Python3 version on Ubuntu https://www.itsupportwale.com/blog/how-to-upgrade-to-python-3-8-on-ubuntu-18-04-lts/
• Data Science Made Simple

Text File Usage

1. with open (“filename.txt”, “r,w,or a”) as f:
   1. text = f.read() or f.readline() or f.readlines()
2. you can try putting the above lines in an exception statement to make sure the file opens
   1. Try:
      1. with—etc
   2. except FileNotFound:
      1. do something here to indicate it
   3. os.path.
      1. isfiles(‘_____’) returns true or false
      2. isdir(‘_____’) returns true or false

Simple Copy to Clipboard

• import clipboard
• clipboard.copy(“______”)
• textcopied = clipboard.paste()

Hints on Using Tkinter

• Frame Border
  • highlightbackground = “enter color here” (puts a border with your chosen color around the frame)
  • highlightthickness = 20 (changes the thickness of the border)
• PhotoImage(file = “____”).subsample(x,y) ==> shrinks photo depending on the numbers you put in x and y, for example 10 and 10
• PhotoImage(file = “____”).zoom(x,y) ==> enlarges photo depending on the numbers you put in x and y
• pack()
  • side = LEFT, RIGHT, TOP, BOTTOM
  • fill = x, y, BOTH
  • padx= , pady= (external)
  • ipadx= , ipady= (internal)
• grid()
  • row, column
  • padx= , pady= (external)
  • columnspac
  • rowspan
• place()
  • x= , y= coordinates
  • fill, relx, rely, padx, etc.
• Treeview
  • style = ttk.Style()
  • style.configure(“Treeview:
    • background = “color”,
    • foreground = “color”,
    • rowheight = 25,
    • fieldbackground = “color”)
  • style.map(‘Treeview’)
  • style.theme_use(“clam or default or alt”)
• Copying information to the main clipboard with Tkinter Where ‘root’ is the main window
  • root.clipboard_clear()
  • root.clipboard_append()
  • root.clipboard_get()
• Bind
  • tkinterobject.bind(event, action)
  • tkinterobject.bind(““, command)
    • Button-1 (left mouse button) and Button-3 (right mouse button)
    • Enter, Leave, Focus
    • Return (main enter key)
    • KP_Enter (keypad enter key)
    • myButton.bind(“<Leave>”, clicker) #On loss of focus#
    • myButton.bind(“<FocusIn>”, clicker) #Triggers event on tab into button
    • myButton.bind(“<Enter>”, clicker) #Triggers button when hover over it
    • myButton.bind(“<FocusOut>”, clicker) #Triggers on loss of focus
    • myButton.bind(“<Return>”, clicker) #Left Click
    • myButton.bind(“<Key>”, clicker) #Focus on button and hit on a key

• tkinterobject.bind(“<Key>”, command) == put event.keysym in the command to find the name of the key you pressed
• windows to top and background
  • window.lower() #puts the tkinter window (root) into the background
  • window.lift() #puts the tkinter window (root) into the foreground
  • window.attributes(‘-topmost’,True) #keeps window on top at all times
• getting help information on tkinter objects
  • my_help = str(help(________)) #where you fill in the blank with the tkinter object, example: Label, Entry, etc.
  • print(my_help) #will print the help information on the object to the terminal

Python Modules

• dearpygui
• moviepy
• twillo
• advanced python scheduler
• vpython (for vector 3D graphics)
• openpyxl (for working with Excel files or LibreCalc files with xlsx extensions)
• pandas (installing pandas will automatically install numpy)
• numpy
• xlrd (for reading xlsx files)
• pandas-ods-reader <https://pypi.org/project/pandas-ods-reader/>
• pysimpleGUI
• dataset (python module for connecting to database with simple commands)
• might work for dealing with LibreOffice and LibreCalc odf files
  • odfpy, ezodf, pyexcel-ods, py-odftools, simpleodspy, pandas-ods-reader

Python VS JavaScript – what are the key differences? Estefania dives deep into both languages to explore how they handle loops, conditional logic, data types, input/output, and more. (20 minute read): https://www.freecodecamp.org/news/python-vs-javascript-what-are-the-key-differences-between-the-two-popular-programming-languages/

Opencv Hints

Installing Instructions

• pip 3 install opencv-python or python3 -m pip install opencv-python
  • may need additional installation of:
    • pip3 install scikit-build
    • pip3 install cmake

• for programming use import cv2

Web Scraping Hints

BeautifulSoup

• Real Python Beautiful Soup Reference
• Dataquest Beautiful Soup Tutorial
• Examples of using CSS Selectors
  • soup.select(‘p’)
  • soup.select(‘p a’) #find the ‘a’ tag within the ‘p’ tag
  • soup.select(‘p, a’) #find both the ‘a’ tag and the ‘p’ tag
  • soup.select(‘.class’)
  • soup.select(‘tag.class’)
  • soup.select(‘tag#ID’)
• Use the inspect in browser, go to console tab
  • this will allow you to see what information is located in the CSS selector
  • $$(‘_________’) where the blank is the CSS Selector to test

MySql Database = possible hints to get it to work on Raspberry Pi

apt install mariadb-client mariadb-common mysql-common libmariadb-dev-compat libmariadbclient-dev

MySQL

• http://recipes.item.ntnu.no/setting-up-an-sql-database-on-the-raspberry-pi/
• https://betterprogramming.pub/how-to-install-mysql-on-a-raspberry-pi-ad3f69b4a094
• https://www.raspberrypi.org/forums/viewtopic.php?t=272183
• https://mariadb.com/resources/blog/how-to-connect-python-programs-to-mariadb/

SQLite Hints

• Adding a column to an existing table: ALTER TABLE
  • addcolumn = “ALTER TABLE _________ ADD COLUMN ________ varchar(32)
  • cur.execute(addcolumn)
  • where the first blank is the table name and the second blank is the name of the column to add
  • ALTER TABLE table name
  • ADD COLUMN column ______ definition; (example for blank is “column name text”
• Exporting data from an SQLite database
  • Using a program SQLite3
    • sudo apt install sqlite3
  • SQLite Export using Python
    • with open(‘outputfile.csv’, ‘wb’) as f:
      • writer = csv.writer(f)
      • writer.writerow([‘col1’, ‘col2’, ……])
      • writer.writerows(data)

Virtual Environment for Python

• On macOS and Linux:
  • python3 -m pip install –user virtualenv (to install)
  • python3 -m venv env (to create in the working directory)
  • to start the virtual environment in the working directory, type ‘source env/bin/activate’ (where env is the environment’s name)
  • to check if virtual environment is working
    • type ‘which python’
    • should show that you are using python3 in ‘…/env/bin/python3’
• On Windows:
• py -m pip install –user virtualenv

Creating a virtual environment:
To create a virtual environment, go to your project’s directory and run venv. If you are using Python 2, replace venv with virtualenv in the below commands.
On macOS and Linux:
python3 -m venv env
On Windows:
py -m venv env
The second argument is the location to create the virtual environment. Generally, you can just create this in your project and call it env or virt.
venv will create a virtual Python installation in the env folder.

Note You should exclude your virtual environment directory from your version control system using .gitignore or similar.

Activating a virtual environment
On macOS and Linux:
source env/bin/activate
On Windows:
.\env\Scripts\activate

Leaving the virtual environment
Simply run: deactivate

Clearing / Emptying a List
thelistsname.clear()

Hints for PySimpleGUI

• import PySimpleGUI as sg Link to setting up and basic syntax
• sg.theme(“themename”) Link to sample themes
  • sg.theme(‘guess’) #will give you a list of possible themes in the terminal view
• sq.CalendarButton(“cal”)
• http://Trinket.pysimplegui.org
• http://PySimpleGUI.com
• replit.com #website with online IDE
• sg.Column(col_layout)
• sg.Frame(‘title here’, frame_layout)
• sg.TabGroup([sg.Tab(), —>list of tabs])
• possible functions
  • popup_get_folder(‘text for popup here’)
  • popup_scrolled()
  • pad = (L, R) #substitute integers, example (3,6)
  • pad = ( (L,R), (T,B) )
  • text_color = ‘___ ‘
  • background_color =’___ ‘
  • enable_events = True
  • tooltip = ‘the tip goes here’
  • font = (‘Courier 14’)
  • use_ttk_buttons = True
  • justification = ‘r’ (or center or left)
  • target = “key of another element”
  • for use with the window, not for the layout
    • keep on top
    • no_titlebar = True
    • grab_anywhere = True
    • alpha_channel = .8 #makes the window transparent with levels from 0 to 1
• Creating a function to create a row in a layout
  • def DataIn(text, key):
    • return[layout row where you replace the text and the key
    • BTW, can also do this directly without the replacement variables
• Chooser Buttons
  • sg.FileBrowse()
  • FilesBrowse
  • FolderBrowse
  • CalendarButton
  • ColorChooserButton
  • sg.FileSaveAs

Pip Freeze and Requirements Text File

pip freeze will produce a similar list of the installed packages, but the output uses the format that pip install expects. A common convention is to put this list in a requirements.txt file:

(tutorial-env) $ pip freeze > requirements.txt
(tutorial-env) $ cat requirements.txt
novas==3.1.1.3
numpy==1.9.2
requests==2.7.0

The requirements.txt can then be committed to version control and shipped as part of an application. Users can then install all the necessary packages with install -r:

(tutorial-env) $ python -m pip install -r requirements.txt

You can install multiple python modules manually using: pip install module1 module2 module3 etc

Hints on use of OS Module with Python

• os.mkdir(‘put-new-dir-name-here’)
• os.chdir(‘put-new-working-dir-here’)
• os.getcwd()
  • gives you your current working directory
• os.chdir(‘..’)
  • moves you Up (back) one directory level
• os.listdir()
  • dirlist = os.listdir()
    • creates a variable with the names of the directories
• os.rmdir(‘put-directory-name-here-that-you-want-removed, deleted’)
• os.uname()
• os.remove(‘put-name-of-file-to-remove-here’)
• os.rename(‘old-name’, ‘new-name’)
• open a file
  • f = open(‘filename-here’, ‘w’)
    • ‘w’ opens the file to write
    • ‘r’ opens the file to read
    • ‘a’ opens the file to append
    • can use a combination as needed, ‘rw’
  • f.write(‘line-you-want-in-file’)
  • f.read()
    • reads the file into memory or a variable
  • f.close()
    • best to close a file after opening it
    • do not need to use this if using ‘f’ in a while statement

Hints on Using Lists

• ‘list += another list’ is the same as ‘list = list + another list’
  • can be used to create complex layouts with PySimpleGUI
• Adding a list to the end of another list
  • list1 = []
  • list2 = []
  • list1.extend(list2)
  • adds list2 to the end of list1

Hints on Using the requests-html library

• item = response.html.xpath(‘ _________ “)
  • print(item)
• item = response.html.find(‘ ________ ‘, first=True).text
  • if trying to find a class use ‘.nameofclass’ in the blank above
  • if trying to find an ID use ‘#nameofID’ in the blank above

Hints on Using the Helium module

• Helium Cheatsheet
• from helium import *
• start_chrome(url=url, headless=False)
• helium.
  • go_to(url)
  • set_driver(driver path)
  • get_driver()
  • write(‘text’, into=”____”)
  • press(“key”)
  • press(ENTER)
  • press(CONTROL+”key”)
  • click(“element”) doubleclick(“element”)
  • click(Button(“OK”))
  • click(Point(200,300))
  • click(ComboBox(“File Type”).top_left+(50,0))
  • find_all()

How to Automatically Install Required Packages From a Python Script?

• https://www.geeksforgeeks.org/how-to-automatically-install-required-packages-from-a-python-script/?ref=rp
• pip3 install pipreqs
• Go to the directory in which your python script is present
• In this directory run the following command that will create a requirement file.
  • pipreqs
• pip3 install -r requirements.txt
• https://www.geeksforgeeks.org/12-pip-commands-for-python-developers/?ref=rp

Installing Chromedriver For Selenium

• Make it executable and move to /usr/local/share
  • chmod +x ~/Downloads/chromedriver
  • sudo mv -f ~/Downloads/chromedriver /usr/local/share/chromedriver
• Create symbolic links
  • sudo ln -s /usr/local/share/chromedriver /usr/local/bin/chromedriver
  • sudo ln -s /usr/local/share/chromedriver /usr/bin/chromedriver
• https://bangladroid.wordpress.com/2016/08/10/how-to-install-chrome-driver-in-linux-mint-selenium-webdriver/
• Possible New Chrome Testing Browser for Chromedriver 116
  • https://developer.chrome.com/blog/chrome-for-testing/
  • https://googlechromelabs.github.io/chrome-for-testing/
  • https://stackoverflow.com/questions/76913935/selenium-common-exceptions-sessionnotcreatedexception-this-version-of-chromedri

list comprehension = a way to create a new list with less syntax

• can mimic certain lambda functions, easier to read
• list = [expression for item in iterable]
• list = [expression for item in iterable if conditional]
• list = [expression if/else for item in iterable]
• Example
  • students =[100,90,80,70,60,50,40,30,0]
  • # passed_students = list (filter ( lambda x: x>=60, students))
  • # passed_students =[i for i in students if i>=60]
  • passed_students = [i if i >= 60 else “FAILED” for i in students ]
  • print (passed_students)
    • [100,90,80,70,60, ‘FAILED’, ‘FAILED’, ‘FAILED’, ‘FAILED’ ]
• https://www.youtube.com/watch?v=fcLDzKH_5XM&list=TLPQMTUxMTIwMjNLhhwR0gYtGA&index=3
• Simple code to remember how it works
  • new_list = [new_item for item in list]
  • new_list = [new_item for item in list if condition]
    

Dictionary Methods

• values()
  • users: dict = {1: ‘Mario’, 2: ‘Ted’, 3: ‘Fred’}
  • print(users.values())
• keys()
  • print(users.keys())
• pop()
  • removes a value related to the key
    • users.pop(2)
  • popped = users.pop(2)
  • print(popped) <this would give the key and value that was removed>
• popitem()
• copy()
• get()
• setdefault()
• clear()
• fromkeys()
• items()
• update()

Additional Hints on Python Use in Comments Below: