Lecture Introduction to Python 2024.pptx

Initiation à la programmation en python

1. Introduction to Python

2. What is Python? Python is a popular programming language. It was created by Guido van Rossum, and released in 1991. It is used for: web development (server-side), software development, mathematics, system scripting. Data Science

3. What Can Python Do? Python can be used on a server to create web applications. Python can be used alongside software to create workflows. Python can connect to database systems. It can also read and modify files. Python can be used to handle big data and perform complex mathematics. Python can be used for rapid prototyping, or for production-ready software development.

4. Why Python? Python works on different platforms (Windows, Mac, Linux, Raspberry Pi, etc). Python has a simple syntax similar to the English language. Python has a syntax that allows developers to write programs with fewer lines than some other programming languages. Python runs on an interpreter system, meaning that code can be executed as soon as it is written. This means that prototyping can be very quick. Python can be treated in a procedural, object-oriented, or functional way.

5. Python Syntax vs Other programming Languages Python was designed for readability and has some similarities to the English language with influence from mathematics. Python uses new lines to complete a command, as opposed to other programming languages, which often use semicolons or parentheses. Python relies on indentation, using whitespace, to define scope, such as the scope of loops, functions, and classes. Other programming languages often use curly brackets for this purpose.

6. Python Syntax Python syntax can be executed by writing directly in the Command Line Or by creating a python file on the server, using the .py file extension, and running it in the Command Line

7. Comments in Python Comments are an integral part of any program Single-line comments: indicate what a section of code does Start with # sign # This is a comment ‹#›

8. Comments in Python Multi-line comments or paragraphs: serve as documentation Press the return key after each line, add a new hash mark and continue your comment # This is a pretty good example # of how you can spread comments # over multiple lines in Python Wrap multiple lines comment inside a set of tri """ If I really hate pressing `enter` and typing all those hash marks, I could just do this instead """ ‹#›

9. Comments in Python: Practices Avoid redundancy: Don’t repeat your self; code should have little to no redundacy # print hello world print (“ Hello World”) Avoid Rude comments Use obvious names to variables ‹#›

10. Comments in Python: Practices If you spend too much time explaining what you did, you need to refactor to make your code clearer and more concise. ‹#›

11. cosc175/data ‹#› Variables and Constants constant alphabetic or numeric value that never changes during processing can be any data type can also be used for something that may change at a later date need only be changed in one place written in all capital letters and underscores separating the words. PI = 3.14 MD_TAX_RATE = .06   variable - value does change during process

12. ‹#› Identifiers: variable names Corresponds to memory location or address Naming convention varies from language to language a sequence of letters (a-z, A-Z), underscores (_), and digits (0–9), and must start with a letter or an underscore. No spaces in variable names any number of characters Python is case sensitive Cat # cat Never use special symbols like !, @, #, $, %, etc. Don't start name with a digit. meaningful names: hrsWorked, payRate Be consistent

13. ‹#› Assignment operator = Value assigning differs from equality   variable = expression

14.   variable = expression variable -physical location in computer memory expression constant x = 10; x = PI; another variable to which a value has previously been assigned y = x; a formula to be evaluated y = a* x /2 + 3; ‹#›

15. ‹#› assignment Processor evaluates the right member of an assignment statement to get a single value it places this value in the memory location (variable name) given as the left member. Not a mathematical equation, can't be switched stamp = 14 is a valid assignment statement 14 = stamp is not  The left member of an assignment statement must always be the name of a computer memory location (variable name). It cannot be a constant or formula.

16. ‹#› Assignment Statement What happens in memory numHours = 10; the value 10 is placed in the memory location numWidgets numHours = numHours + 1; numWidget is evaluated. Contains a 10, one is added to 10, 11 is stored at the memory location numWidgets name = "toby" the four characters t-o-b-y are stored in the memory location name (note: The single quotes are used as delimiters and are not stored in memory.) stuff = numHours; Assuming the value 11 in the memory location numWidgets , this assignment statement places the value 11 in stuff (note: Now both stuff and numWidgets have the same value.) hours = numHours * 2 the ALU evaluates the expression on the right and places the value 30 in the memory location widget

17. ‹#› Assignment Statement What happens in memory numHours = 10; the value 10 is placed in the memory location numHours numHours = numHours + 1; numHours is evaluated. Contains a 10, one is added to 10, 11 is stored at the memory location numHours name = "toby" the four characters t-o-b-y are stored in the memory location name (note: The single quotes are used as delimiters and are not stored in memory.) stuff = numHours; Assuming the value 11 in the memory location numHours , this assignment statement places the value 11 in stuff (note: Now both stuff and numHours have the same value.) hours = numHours * 2 the ALU evaluates the expression on the right and places the value 30 in the memory location hours

18. Assignment Operators ‹#›

19. cosc175/operators ‹#› Modules in Python Module: A module is a file containing Python code that can be used by other modules or scripts. A module is made available for use via the import statement. Once a module is imported, any object defined in that module can be accessed using dot notation. import math math.pow(2, 4)

20. ‹#› Relational Operators op operation < Less than <= Less than or equal to > Greater than >= Greater than or equal to == Equal to != Not equal to <> Different from

21. ‹#› Logical Operators