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Introduction to Python

  • What is Python?
  • Python is an Interpreted language
  • Python Resources
  • Text Editors
  • How to Program
  • Comments
  • Extra (depending on time)
    • Simple Operators in Python










What is Python?

  • Python is a general-purpose programming language that can be used to:
    • develop web apps and software
    • write scripts to automate operations within operating systems
    • operate robots and other technical machinery
    • … and more!










Python for Data Science

  • Python is one of many languages in Data Science and Machine Learning. It is by far the most popular.
  • Python is easy to learn, read and write.
  • There are extensive scientific computing libraries and published academic work that uses Python










Start off using repl.it to run your code

  • Easy, cross-platform, share-able
  • The minimum necessary for you to get some code working










Python is an Interpreted Language

  • Interpreted languages are translated into machine code and run at the same time, giving immediate output.
  • In repl.it, you can just hit the “Play” button and see results repl, interpreted lang
  • Interpreted languages: Javascript, Ruby, LISP, many other










Python Documentation and Resources










Text Editors

  • Text editors are used to write plain text (using UTF-8 encoding)
  • DSI and Galvanize courses use VSCode primarily, please install it ASAP
  • Install Anaconda for your operating system, giving you access to Jupyter notebooks and a local Python environment










How to Program

  • Think about the problem
  • Define what it means for the program to be working
  • Create a series of formal steps that lead to a repeatable operation










BREAKOUT (5 minutes)

Write an algorithm for boiling a box of spaghetti

  • Define the steps clearly and at an appropriate level for an extra-terrestrial with good human language skills, who has never cooked pasta before
  • There is no single correct solution here










BREAKOUT SOLUTION EXAMPLE (abbreviated)

  1. Gather cooking implements and supplies a. Take Boiling Pot out of cupboard under the counter b. Take Box of Spaghetti out of cupboard next to refrigerator c. Take Salt from spice rack d. Take oil from shelf next to stove
  2. Prepare water for boiling pasta a. Fill Boiling Pot with water from the tap b. Place Boiling Pot on stove burner c. Turn heat dial clockwise so that it is on high ...










Comments

# this is a single line comment
'''
This
is a 
multi-line
comment
'''










Reasons for using comments

  • Send a message to someone reading your code
  • Exclude some code snippet from running
  • Provide function documentation
  • Leave # TODO: statements in your code, for later development










Basic Python Constructs

  • Common Data Types
  • Simple Operators in Python
  • Assignment Operators










Common Data Types

  • A data type can be thought of as a form in which a piece of data can exist

    • Working with integers, floats, booleans

  • the type() function will tell you the data type

    • ex: type(23) will tell you that 23 is an integer










Number Types: int, float, and bool

  • Integers can be thought of as “whole numbers”
  • Floats can be thought of as “decimal numbers”
  • Ints and floats are encoded differently
    • 1.0 == 1 ?? ⇒ True
    • However, type(1.0) == type(1) ?? ⇒ False










BREAKOUT (3 minutes):

  • Use the type() function to discover the type of the number 74.
  • Using a comment, describe simply what you did on the line above your code snippet










BREAKOUT SOLUTION:

# output to console the type of 74
print(type(74))

NOTE: In general, you will want to avoid writing comments that say what your code is doing, unless, at this stage, it is for your own benefit and study










Simplest Operators in Python

  • Basic Arithmetic Operators: Addition: + Subtraction: - Multiplication: * Division: /
  • PEMDAS
    • Use parentheses (3+5) / 7 to ensure the desired order of operations










Duck Typing

  • Python is a “duck typed” language
    • "If it walks like a duck, and quacks like a duck, then it must be a duck."
    • Effectively, this means that you can perform mathematical operations between similar types, such as ints and floats, because Python infers a general type for the operation.
      • For example, operations between ints and floats will result in floats
      • Division will result in a float










BREAKOUT (5 minutes)

  • Add 5 and 7.2, multiply the result by 6, divide that result by 3, then square the result










BREAKOUT SOLUTION

  • Add 5 and 7.2, multiply the result by 6, divide that result by 3, then square the result
print((((5 + 7.2) * 6) / 3)**2)










Homework