Lecture Introduction to Python 2024.pptx
- 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 7
- 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 """ 8
- 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 9
- 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. 10
- 11. cosc175/data 11 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. 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. 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; 14
- 15. 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. 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. 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
- 19. cosc175/operators 19 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. 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