python_function.pdf
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This document provides an introduction to functions in Python programming. It defines what a function is, how to define and call functions that do and do not return values, and how to work with local and global variables within functions. It also discusses passing arguments to functions and functions that return values. Examples are provided throughout to illustrate key concepts.
python_function.pdf
- 1. Beginnings of programming in Python Functions Artur Machura 16.06.2023, Katowice
- 2. Abstract ▪ Introduction to functions ▪ Defining and calling functions (non- returning and returning values) ▪ Local and global variables/constants ▪ Forwarding function arguments
- 3. Introduction to functions ▪ A function is a set of commands that is used to perform a certain task in a program. ▪ The rationale for using the function is the divide-and- conquer rule (dividing the program into smaller tasks) ▪ A distinction is made between functions that return a value and those that do not return a value Example: command command command command command command command command command Example: def function1(): command command command def function1(): command command command def function1(): command command command
- 4. Defining and calling a function that does not return a value ▪ Program code placed in a function is called a function definition. To execute a function, use the command that calls it. ▪ Naming rules in Python: avoid keywords, no spaces, python is case sensitive, names refer to the task ▪ In the first line is placed the header of the function ▪ The set of commands below the header is called a block ▪ block must be indented (each line starts with the same number of spaces) Example: def main(): print(’ I would like to introduce myself.’) introduce_yourself() def introduce_yourself(): print(’My name is Artur’) main()
- 5. Local variables ▪ A local variable is declared inside a function and cannot be referenced outside of that function (concept of function scope). ▪ The coincidence of names between local variables in different functions does not matter. ▪ Inside the function, the place of the variable is also important (you can refer to a variable declared earlier/higher in the code). Example: def main(): texas() california() def texas(): birds = 5000 print(’Texas has’, birds, ’bird species.’) def california(): birds = 8000 print(’California has’, birds, ’bird species.’) main()
- 6. Global variables and constants ▪ Global variables can be used in all functions in a program file. This is possible when the variable is created outside all functions (see example 1). ▪ If you want to assign a value to a global variable, you must additionally use the global command (see example 2). Example 1: my_value = 10 def show_value(): print(my_value) show_value() Example 2: Number = 0 def main(): global number number = int(input(’Enter the number: ’)) show_number() def show_number(): print(’The figure given is’, number) main()
- 7. Forwarding function arguments ▪ An argument is the data that is passed to a function when it is called. ▪ A parameter is a variable in which the argument passed to the function is stored. ▪ The scope of a parameter usually includes the entire function in which it is defined (commands outside the function cannot access it). ▪ Passing several arguments ▪ Arguments in the form of keywords (see example 2) Example 1: def main(): print(’ 'The sum of the numbers is’) show_sum(12, 45) def show_sum(num1, num2): result = num1 + num2 print(result) Example 2: def main(): show_interest(rate=0.01, periods=10, principal=10000.0) def show_interest(principal, rate, periods): interest = principal * rate * periods print('The amount of interest is ’, format(interest, ’.2f’), sep=’’) main()
- 8. Defining and calling a function that returns a value. ▪ A value return function is a function that returns a value to the component that calls it. ▪ Python offers a library of ready-made functions to perform various operations (the term library function is used). ▪ A function that returns a value contains a return statement that passes the return value to the component that called it (example 2). Example 1: import random def main(): number = random.randint(1, 10) print(’ The number is’, number) main() Example 2: def main(): first_age = int(input(’ Enter your age: ’)) second_age = int(input(’ Enter your age: ’)) total = sum(first_age, second_age) print(’ Together you have’, total) def sum(num1, num2): result = num1 + num2 return result main()
- 9. Source ▪ Gaddis T., Python dla zupełnie początkujących. Wydanie IV. Helion 2019. ▪ Official source form Python community ▪ https://docs.python.org/3.11/tutorial/index.ht ml
- 10. Thank you for your attention! Please submit any comments on the software-engineers.org PhD Artur Machura arturmachura.info