Third-party Libraries
=====================


* The open-source community
* virtual environments
* installing third-party packages - pip

To create a virtual environment, run:

.. code::

 python -m venv filename

To activate a virtual environment Windows, run:

.. code::
 
 .\venv\filename\Scripts\activate

To activate a virtual environment on Unix or MacOS, run:

.. code::

  source filename/bin/activate


* numpy
* pandas
* matplotlib
* flask
* requests
* selenium
* pygame
* plotly
* sympy


`Pygame <https://www.pygame.org/wiki/about>`_
=======

Pygame is a library for writing video games with Python.
To get started the following command in a virtual environment

.. code::

 python pip install pygame

You can check the installation by running the following game:

.. code::

 python -m pygame.examples.aliens

This program creates a window with a small red circle.   The circle will move toward the mouse cursor.

.. code::

 # mouse_chase.py

 import pygame, sys, random
 from pygame.locals import *

 import math

 # set up pygame

 pygame.init()
 mainClock = pygame.time.Clock()
 # Set up the window.
 WINDOWWIDTH = 500
 WINDOWHEIGHT = 500
 windowSurface = pygame.display.set_mode((WINDOWWIDTH, WINDOWHEIGHT),
                                        0, 32)
 pygame.display.set_caption('Mouse Chase')
 
 # set up the colors for the background and the ball
 WHITE = (255, 255, 255)
 RED = (255, 0, 0)
 BLUE = (0, 0, 255)

 SPEED = 4 # controls how quickly ball moves
 c_x = 250 # current x value for the ball initially 250
 c_y = 250 # current y value for the ball initially 250

 # run the game loop forever
 while True:
     # check for a quit event
     for event in pygame.event.get():
         if event.type == QUIT:
             pygame.quit()
             sys.exit()
                      
     # colors the background of the surface
     windowSurface.fill(WHITE)
     
     x = pygame.mouse.get_pos()[0]
     y = pygame.mouse.get_pos()[1]
     
     # updates the position of the ball by moving it slightly toward the mouse
     dy = y - c_y
     dx = x - c_x
     r = math.sqrt(dx**2 + dy**2)+0.0001
     cos = dx/r
     sin = dy/r
     x_speed = int(SPEED*cos)
     y_speed = int(SPEED*sin)
     c_x += x_speed
     c_y += y_speed
     
     # redraws the ball and updates the window
     pygame.draw.circle(windowSurface, RED, (c_x, c_y), 20)
     pygame.display.update()
     

     mainClock.tick(100)