COMP 171:Functions, for loops and rangeJohn Barr

Section 03

Slides by Toby Dragon

What is a function?

a block of code that we can call with a single name. "Black Box"

defined in order to provide functionality without dealing with how it works

Some functions are provided to you: input (), print ()

Some functions you have written:drawRect(length, width)

Why functions?

break code into smaller, functional pieces testing parts before trying to solve everythingMake pieces that can be reused for multiple

purposes

simplify (abstract) to make your program easier to understand and to use

Functions: defining the "Black Box"

def drawInitials ():

Tell p

ython w

e're

defining a fu

nction

"Name" t

hat we decid

e

place fo

r parameters

(empty if n

one)

tells pyth

on that th

e functi

on

is sta

rting, e

veryt

hing indented

after t

his will

be part of th

e functi

on

Parameters

def drawInitials ():

def drawSquare (size):

def drawRect (length, width):

No parameters

One parameter

Two parameters

Parameters

Parameters answer questions the function has.e.g., drawRect needs to know the length and

width of the rectangle you want drawn

Use parameters only when necessary!

Practice

Write a function that takes the temperature in Fahrenheit and prints the temperature in Celsius.

To calculate Celsius from Fahrenheit: subtract 32 multiply by 5/9

Practice

Write a function that takes the temperature in Fahrenheit and prints the temperature in Celsius.

To calculate Celsius from Fahrenheit: subtract 32 multiply by 5/9

Functions: using the "Black Box"

when we use a function, we say we are calling the function.

Always end in parentheses! Otherwise, python treats it as a variable

Between parentheses you give values to the parameters

Calling functions and sending Parameters drawInitials ()

drawSquare (100)

sides=100 ends = 200 drawInitials (sides, ends)

the for loop

for num in range(0, 10, 1):

indented code below it will happen multiple times, each with num = a number from the range.

varia

ble you cr

eate

range functi

on

Repetition: the range function

range (10) – give each number,

starting at 0 to less than 10

range (3, 10) – give each number,

starting at 3 to less than 10

range (2, 20, 2) – give each number

starting at 2, to less than 20, and count by 2

name of the

range functi

on

Parameter(s)

Repetition: range practice

[0, 1, 2, 3, ..., 19]

[2, 4, 6, ..., 46, 48]

[50, 48, ..., 0]

Repetition: for loop practice

Write a for loop that prints:3

6

9

…

18

for loop practice

Write a program to print the Celsius equivalent of every 10 degrees Fahrenheit between 0 and 100.

Use your function from earlier!