Python

Python tips and tricks

Python Development

• Use virtualenv and virtualenvwrapper for development of isolated environment.

  1. You should have a basic working pip tool setup available.(Python2: pip2/ Python3: pip3)
     Use the distributions package manager to install the pip tool.
  2. Follow the step to install virtualenv and virtualenvwrapper:

     # Use pip2 or pip3 according to the availabilty.
     # Referenced here as `pip`
     pip install --user virtualenv virtualenvwrapper

     Note: You should have $HOME/.local/bin in your $PATH environment variable.
  3. Setting up a virtualenvwrapper environment:

     # Setup following lines in your ~/.bashrc
     export WORKON_HOME=$HOME/apps/pyenv
     # Locate Python3 executable using this command: $ which python3
     export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3
     source ~/.local/bin/virtualenvwrapper.sh

  4. Creating a virtualenvironment:

     # For default Python 3 Environment
     mkvirtualenv py3grip
     # Check Virtualenv Python version
     python --version
     pip install grip
     # For Python 2 Environment
     mkvirutalenv py2grip -p python2
     # Check Virtualenv Python version
     python --version
     pip install grip

  5. Activating the environment:

     workon py3grip

  6. De-activating the virtual environment:

     deactivate

NOTE: Refer the documentation of virtualenvwrapper for user-defined hooks for setting up a development environment for C/C++ Projects.

---

Old steps

3. Setting up a virtual environment for development:  
   **Only one python executable can be used for the virtual environment setup.**
    ```sh
    # For Python2 Development
    virtualenv -p /usr/bin/python2.7 my_project
    # For Python3 Development
    virtualenv -p /usr/bin/python3 my_project
    ```
4. Activating the virtual environment:  
   For Linux:
    ```sh
    source my_project/bin/activate
    ```
   For Windows:
    ```bat
    .\my_project\Scripts\activate
    ```
5. De-activating the virtual environment:
    ```sh
    deactivate
    ```

---

Utilities

• Simple and easy accessible webserver for quick file sharing.

  # For python 2.x
  python -m SimpleHTTPServer <custom_port_number>
  
  # For Python 3.x
  python3 -m http.server

• Simple Python HTTPS Server.

  #!/usr/bin/python
  # taken from http://www.piware.de/2011/01/creating-an-https-server-in-python/
  # generate server.xml with the following command:
  #    openssl req -new -x509 -keyout server.pem -out server.pem -days 365 -nodes
  # run as follows:
  #    python simple-https-server.py
  # then in your browser, visit:
  #    https://localhost:4443
  
  import BaseHTTPServer, SimpleHTTPServer
  import ssl
  
  httpd = BaseHTTPServer.HTTPServer(('localhost', 4443),
  SimpleHTTPServer.SimpleHTTPRequestHandler)
  httpd.socket = ssl.wrap_socket (httpd.socket, certfile='./server.pem',
  server_side=True)
  httpd.serve_forever()

  Note: For key and certificate generation kindly search online for better generation process.

Notes:

1. By default port number is: 8000.
2. The HTTP Server is unsecured!!!, anybody with network access can access the directory from where the script is started.
3. Kindly use it only on Private and Trusted Network.

Tools and Libraries

List of Python libraries and tools:

NOTE: Use the virtualenvwrapper to create separate virtual environment for these libraries/tools as they might have conflicting dependencies.

Available as command line

pip install --user \
                   flask \
                   gdbgui \
                   grip \
                   jupyter \
                   matplotlib \
                   numpy \
                   scipy

To-Do

1. Securing the Jupyter NoteBook installation.
2. Add Code for QRCode Generator.
3. Add the Python API Tracer.
4. ......

CTypes Example

• Ctypes library for calling C/C++ API's from python.
• Simple example available in ctypes directory.
• flask_tutorial: An exploration of Flask Tool.
• Jinja2: An exploration of Templating Engine can be used along with Flask
• Mako: An exploration of another Templating Engine.