Module 4 - Functions Flashcards
What is a function?
A group of statements in a program that perform a specific task
A function is a block of code which only runs when it is called. You can pass data, known as parameters, into a function. A function can return data as a result.
What is the ‘divide and conquer’ approach?
The problem is divided into smaller sub-problems and then each problem is solved independently
What is modularized programming?
Each task within the program is in its own function
(you have a dishwasher, washing machine, robot vacuum - if one breaks, the other machines won’t be disturbed = MODULARIZATION!)
What is a void function?
Simply executes the statements it contains then terminates or stops, without returning a value
What is a value-returning function?
Executes the statements it contains, and then it returns a value back to the statement that called it
What are the rules for naming functions?
- can only contain numbers, letters and underscores
- cannot start with a number
- cannot use keywords
- case sensitive!
Define function syntax
def function_name():
____statement1
____statement2
What are the different parts of a function?
Header = keyword and function name, followed by paranthesis and a colon
Body (called blocks) = indented statements included in the function
What are the three important things to consider when defining a function?
- Major goal of the function (this will define the statements inside the function)
- What input data does it need (this will specify the argument list)
- What value does it need to give back to the caller (this is the return value)
Write a function to determine the larger of two numbers and print it. Then call that function with numbers 7 and 3.
def large_num(num1,num2): \_\_\_if num1>num2: \_\_\_\_\_\_\_print(num1) \_\_\_else: \_\_\_\_\_\_\_print(num2)
large_num(7,3)
What is the main function?
A function that activates (calls) other functions when they are needed
Main function is called when the program starts
What does a function look like in a flowchart?
Function call shown as rectangle with vertical bars at each side
Function name is written inside the rectangle
End terminal symbol usually reads ‘return’
Typically draw a separate flowchart for each function
What is top down design?
A technique for breaking algorithm into functions
What does a hierarchy (structure) chart do?
Depicts relationship between functions
Boxes represent functions; lines connecting boxes represent the functions called by each function
What is the math module?
Part of standard library that contains functions that are useful for performing mathematical calculations
How do you access the math module?
Use import statement “import math”
How do you access the math functions?
To access one of the functions, you have to specify the name of the module and the name of the function, separated by a dot (also known as a period). This format is called dot notation:
math. sin(x)
math. pi
Does the argument of a function have to be a literal?
No, the argument of a function can be any kind of expression, including arithmetic operators:
x = math.sin(degrees / 360.0 * 2 * math.pi)
And even function calls:
x = math.exp(math.log(x+1))
Almost anywhere you can put a value, you can put an arbitrary expression
How do you end a function?
Enter an empty line
What do you have to keep in mind with flow of execution and functions?
You must define a function before it is called
What are parameters?
Variables that arguments get assigned to
When you define a function, the parameter is what’s in the parentheses
Then, when you call it, you enter in your arguments
T/F: when you create a variable inside a function, it is local
True
Are parameters local or global variables?
Local
Is print_twice a void or value-returning function?
Void because it simply performs the task (print the argument twice) without returning a value
How can you tell if a function is void or value-returning?
If you assign the result to a variable, then print(variable) the output will be a value called ‘none’
Is the value ‘none’ the same as the string ‘none’?
No, it is a special value with its own type ‘NoneType’
Write the code to call a function named send_variable and that expects a single int parameter.
Suppose a variable called x refers to an int. Pass this variable as an argument to send_variable.
send_variable(x)
What is the syntax of a statement that calls a function?
function_name()
*MUST INCLUDE parentheses even if no arguments!!!
Given that add, a function that expects two int parameters and returns their sum, and given that two variables, euro_sales and asia_sales, have already been defined:
Write a statement that calls add to compute the sum of euro_sales and asia_sales and that associates this value with a variable named eurasia_sales.
eurasia_sales=add(euro_sales,asia_sales)
