Python 3.7.3 : Using the pipenv tool.

The goal of this tutorial is how to use pipenv and manage dependencies and development environments on a collaborative Python project.
The documentation area can be found here.

C:\Python373>cd Scripts

C:\Python373\Scripts>pip install --user pipenv
Collecting pipenv
...
Successfully installed pipenv-2018.11.26 virtualenv-clone-0.5.3

If you see errors like this:
WARNING: The scripts pipenv-resolver.exe and pipenv.exe are installed in 'C:\Users\....'

which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, 
use --no-warn-script-location.

You need to add this path show into the WARNING to the windows path, see command:

setx path "%path%;C:\Users\..\Python37\Scripts"

Let use this tool to install a requests package:

C:\Python373\Scripts>cd ..

C:\Python373>cd my_flask

C:\Python373\my_flask>pipenv install requests
Creating a virtualenv for this project.
Pipfile: C:\Python373\my_flask\Pipfile
Using c:\python373\python.exe (3.7.3) to create virtualenv.
[  ==] Creating virtual environment...Already using interpreter c:\python373\pyt
hon.exe
Using base prefix 'c:\\python373'
New python executable in C:\Users\catafest\.virtualenvs\my_flask-j9hGDZgP\Script
s\python.exe
Installing setuptools, pip, wheel...
done.
Successfully created virtual environment!
Virtualenv location: C:\Users\catafest\.virtualenvs\my_flask-j9hGDZgP
Creating a Pipfile for this project.
Installing requests.
Adding requests to Pipfile's [packages].
Installation Succeeded
Pipfile.lock not found, creating.
Locking [dev-packages] dependencies.
Locking [packages] dependencies.
Success!
Updated Pipfile.lock (444a6d)!
Installing dependencies from Pipfile.lock (444a6d).
  ================================ 5/5 - 00:00:04
To activate this project's virtualenv, run pipenv shell.
Alternatively, run a command inside the virtualenv with pipenv run.

The syntax for the Pipfile is TOML, and the file is separated into sections. [dev-packages] for development-only packages, [packages] for minimally required packages, and [requires] for other requirements like a specific version of Python
If you got this error you need restarts the command prompt:

'pipenv' is not recognized as an internal or external command,
operable program or batch file.

The next command let us see output diagnostic information for use in GitHub issues:

C:\Python373\my_flask>pipenv --support | clip
C:\Python373\my_flask>pipenv --support

Check for security vulnerabilities (and PEP 508 requirements) in your environment with:

C:\Python373\my_flask>pipenv check
Checking PEP 508 requirements.
Passed!
Checking installed package safety.
All good!

Let's use the example from the documentation webpage:

import requests

response = requests.get('https://httpbin.org/ip')

print('Your IP is {0}'.format(response.json()['origin']))

The result works great.

C:\Python373\my_flask>pipenv run python my_ip.py
Your IP is ...

You can print out a tree-like structure showing your dependencies.

C:\Python373\my_flask>pipenv graph
requests==2.22.0
  - certifi [required: >=2017.4.17, installed: 2019.6.16]
...

Using this command will see a reversed tree may be more useful when you are trying to figure out conflicting sub-dependencies.

C:\Python373\my_flask>pipenv graph --reverse
certifi==2019.6.16
  - requests==2.22.0 [requires: certifi>=2017.4.17]
chardet==3.0.4
...

This command installs all the dependencies needed for development:

C:\Python373\my_flask>pipenv install --dev
Installing dependencies from Pipfile.lock (444a6d).
  ================================ 5/5 - 00:00:10
To activate this project's virtualenv, run pipenv shell.
Alternatively, run a command inside the virtualenv with pipenv run.

You can uninstall a python module:

pipenv uninstall numpy

You can replace --all with --all-dev to just remove dev packages.
Let’s start a shell in a virtual environment to isolate the development of this app:

C:\Python373\my_flask>pipenv shell
Launching subshell in virtual environment.
Microsoft Windows [Version 6.3.9600]
(c) 2013 Microsoft Corporation. All rights reserved.

(my_flask-j9hGDZgP) C:\Python373\my_flask>

The package name, together with its version and a list of its own dependencies, can be frozen by updating the Pipfile.lock with the lock keyword.

(my_flask-j9hGDZgP) C:\Python373\my_flask>pipenv lock
Locking [dev-packages] dependencies.
Locking [packages] dependencies.
Success!
Updated Pipfile.lock (444a6d)!

Clears caches (pipenv, pip, and pip-tools) with:

pipenv --clear

Remove the virtualenv created:

(my_flask-j9hGDZgP) C:\Python373\my_flask>pipenv --rm

Close the pipenv shell:

(my_flask-j9hGDZgP) C:\Python373>exit

C:\Python373\my_flask>

This tool requires special attention in developing and programming with Python, so we have only traveled some of its real possibilities.

Python 3.7.3 : Using the werkzeug.

From the official webpage, you can see all the features of this python module:
Werkzeug is a comprehensive WSGI web application library. It began as a simple collection of various utilities for WSGI applications and has become one of the most advanced WSGI utility libraries.
It includes:
An interactive debugger that allows inspecting stack traces and source code in the browser with an interactive interpreter for any frame in the stack.
A full-featured request object with objects to interact with headers, query args, form data, files, and cookies.
A response object that can wrap other WSGI applications and handle streaming data.
A routing system for matching URLs to endpoints and generating URLs for endpoints, with an extensible system for capturing variables from URLs.
HTTP utilities to handle entity tags, cache control, dates, user agents, cookies, files, and more.
A threaded WSGI server for use while developing applications locally.
A test client for simulating HTTP requests during testing without requiring running a server.
The documentation of this python module can be found here.
You can install this python module with the pip tool:

pip install -U Werkzeug

This module can install it if you install the flask python module with python 3.7.3.
Let's test it:

C:\Python373>python
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 21:26:53) [MSC v.1916 32 bit (Intel)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> from werkzeug.wrappers import Request, Response
>>>
>>> @Request.application
... def application(request):
...     return Response('Hello, World!')
...
>>> if __name__ == '__main__':
...     from werkzeug.serving import run_simple
...     run_simple('localhost', 4000, application)
...
 * Running on http://localhost:4000/ (Press CTRL+C to quit)
127.0.0.1 - - [16/Jul/2019 13:29:44] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [16/Jul/2019 13:29:46] "GET /favicon.ico HTTP/1.1" 200 -

If you run this source code and open your browser with this http://localhost:4000/ address then you will see a text with Hello, World!.
The common uses of this python package are:

>>> from werkzeug.wrappers import Request, Response
>>> from werkzeug.routing import Map, Rule
>>> from werkzeug.exceptions import HTTPException, NotFound
>>> from werkzeug.wsgi import SharedDataMiddleware
>>> from werkzeug.formparser import parse_form_data
>>> from werkzeug.utils import redirect
>>> from werkzeug.utils import escape
>>> from werkzeug.serving import run_simple

Let's test another simple application with werkzeug python module:

from werkzeug.serving import run_simple
from werkzeug.wrappers import Request
from werkzeug.wrappers import Response

class Application(object):
    def __init__(self):
        print('init Application class')

    def dispatch_request(self, request):
        return Response("Logged in as %s" % request.authorization)

    def __call__(self, environ, start_response):
        request = Request(environ)
        auth = request.authorization
        response = self.dispatch_request(request)
        return response(environ, start_response)

if __name__ == "__main__":
    application = Application()
    run_simple("localhost", 5000, application)

The result will be this:

C:\Python373>python.exe werkzeug_001.py
init Application class
 * Running on http://localhost:5000/ (Press CTRL+C to quit)
127.0.0.1 - - [16/Jul/2019 14:05:31] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [16/Jul/2019 14:05:32] "GET /favicon.ico HTTP/1.1" 200 -

You can add more features to this source code and check with werkzeug features of Web Server Gateway Interface (WSGI).
A full list with examples can be found here.

Python 3.7.3 : Programming Krita.

Today I wrote a python tutorial about Krita software and programming python.
The Krita software use python version 3.6.2.

==== Warning: Script not saved! ====
3.6.2 (v3.6.2:5fd33b5, Jul  8 2017, 04:57:36) [MSC v.1900 64 bit (AMD64)]

The full tutorial can be found at my Blogspot (a Blogspot about the graphics area).

Python 3.7.3 : Simple tests with zipfile python module.

You can read about this python module here.
The ZIP file format is a common archive and compression standard. This module provides tools to create, read, write, append, and list a ZIP file. Any advanced use of this module will require an understanding of the format, as defined in PKZIP Application Note.

This module does not currently handle multi-disk ZIP files. It can handle ZIP files that use the ZIP64 extensions (that is ZIP files that are more than 4 GiB in size). It supports decryption of encrypted files in ZIP archives, but it currently cannot create an encrypted file. Decryption is extremely slow as it is implemented in native Python rather than C.

C:\Python373> python -m zipfile -c test.zip test.html  textalongpath.pdf
C:\Python373> python -m zipfile -c test_folder.zip test.html  temp
C:\Python373>python -m zipfile -l  test.zip
File Name                                             Modified             Size
test.html                                      2019-07-11 10:46:58         6115
textalongpath.pdf                              2019-06-08 22:55:50           84

C:\Python373>python -m zipfile -l  test_folder.zip
File Name                                             Modified             Size
test.html                                      2019-07-11 10:46:58         6115
temp/                                          2019-07-07 21:36:42            0
temp/wlop/                                     2019-07-07 21:36:42            0

This lines of code will create two archives named test.zip and test_folder.zip with the files shown on each command.
For extraction, is need to use the -e argument:

C:\Python373>python -m zipfile -e test.zip zipfiles/

C:\Python373>python -m zipfile -e test_folder.zip zipfiles/

C:\Python373>cd zipfiles

C:\Python373\zipfiles>dir
...

Let's using this python module inside python:

C:\Python373>python.exe
Python 3.7.3 (v3.7.3:ef4ec6ed12, Mar 25 2019, 21:26:53) [MSC v.1916 32 bit (Inte
l)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import zipfile
>>> import datetime
>>> my_zip = zipfile.ZipFile('test.zip','r')
>>> print (my_zip.namelist())
['test.html', 'textalongpath.pdf']
>>> def print_info(archive_name):
...     my_zip = zipfile.ZipFile(archive_name)
...     for info in my_zip.infolist():
...             print (info.filename)
...             print ('Comment: ', info.comment)
...             print ('Modified: ', datetime.datetime(*info.date_time))
...             print ('System: ', info.create_system, '(0 = Windows, 3 = Unix)'
)
...             print ('ZIP version: ', info.create_version)
...             print ('Compressed: ', info.compress_size, 'bytes')
...             print ('Uncompressed: ', info.file_size, 'bytes')
...
>>> print_info('test_folder.zip')
test.html
Comment:  b''
Modified:  2019-07-11 10:46:58
System:  0 (0 = Windows, 3 = Unix)
ZIP version:  20
Compressed:  1679 bytes
Uncompressed:  6115 bytes
temp/
Comment:  b''
Modified:  2019-07-07 21:36:42
...

Extract all files from an archive:

>>> from zipfile import ZipFile
>>> with ZipFile('test.zip','r') as zipObj:
...     zipObj.extractall()

Extract files by extension:

>>> with ZipFile('test.zip', 'r') as zipObj:
...    listOfFileNames = zipObj.namelist()
...    for fileName in listOfFileNames:
...        if fileName.endswith('.html'):
...            zipObj.extract(fileName, 'new.html')
...
'new.html\\test.html'

Create a new arhive named The_new.zip and add the new.html file on it.

>>> zipObj = ZipFile('The_new.zip','w')
>>> zipObj.write('new.html')
>>> zipObj.close()
>>> print_info('The_new.zip')
new.html/
Comment:  b''
Modified:  2019-07-14 22:15:58
System:  0 (0 = Windows, 3 = Unix)
ZIP version:  20
Compressed:  0 bytes
Uncompressed:  0 bytes

Python 3.7.3 : Three examples with BeautifulSoup.

Beautiful Soup is a library that makes it easy to scrape information from web pages. It sits atop an HTML or XML parser, providing Pythonic idioms for iterating, searching, and modifying the parse tree., see the pypi webpage.
This python module was created by Leonard Richardson.
A large definition can be this:
Web Scraping (also termed Screen Scraping, Web Data Extraction, Web Harvesting, etc.) is a technique employed to extract large amounts of data from websites whereby the data is extracted and saved to a local file in your computer or to a database in table (spreadsheet) format.
This python module can do that but the input format and output format is different.
The input can be a webpage like an URL or webpage with all pieces of information and the output depends by the this and the user choices.
Les's see some examples:
First example show you how to take content of the first row table from a wikipedia webpage.

# get table from wikipedia 
import requests
from bs4 import BeautifulSoup
website_url = requests.get('https://en.wikipedia.org/w/index.php?title=Table_of_food_nutrients').text
soup = BeautifulSoup(website_url,'lxml')

my_table = soup.find('table',{'class':'wikitable collapsible collapsed'})
links = my_table.findAll('a')
Food = []
for link in links:
    Food.append(link.get('title'))

print(Food)

The next example takes all files from a page

# get links using the url
import urllib
from bs4 import BeautifulSoup
page = urllib.request.urlopen('http://____share.net/filmes/').read()
soup = BeautifulSoup(page)
soup.prettify()
for anchor in soup.findAll('a', href=True):
    print (anchor['href'])

The last example takes all images from the search query of imgur website:

# get images from imgur search query
import urllib
from bs4 import BeautifulSoup
url = 'https://imgur.com/search/score?q=cyborg'
with urllib.request.urlopen(url) as f:
    soup = BeautifulSoup(f.read(),'lxml')

a_tags = soup.findAll("a",{"class":"image-list-link"})
img_tags = [a.find("img") for a in a_tags]
print(img_tags)
srcs = []
for s in img_tags:
    src_tags=('http:'+s['src'])
    srcs.append(src_tags)

print(srcs)

As a conclusion, this module will pose problems for those who do not understand how to scroll through the source code, the content of web pages, how to read 'lxml', 'page', etc.
It will greatly help your Chrome F12 key to access parts of web content.