If Statements Example

Example

Result World

Quick Docs

If statements:

if balls_present():
    commands to execute

For loop:

for i in range(#):
    commands to execute

Karel’s basic commands:

move()
turn_left()
turn_right()
turn_around()
put_ball()
take_ball()

14: If Statements Example

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for i in range(8):
    move()
    if balls_present():
        take_ball()
move()
 
 
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Run! Reset

Errors:

Looks like something is taking longer than usual. We stopped running your code. Please try again.

HINT: You might have an infinite loop in your code.

5 points

This program has Karel walk down the street and pick up litter as she goes. You can change the world to see how Karel’s cleanups are impacting the amount of litter from week to week. Notice how the if statement enables Karel to use the same program to clean up her community even when the litter is in different places!

Exploration Questions:

How does changing the world impact the program?
What happens when you move the first move() command to inside of the if statement?
What happens when you change the number inside the for loop?

Ending World

Karel's Built in Commands

Karel Commands

`move()` Python		`turn_left()` Python
`put_ball()` Python		`take_ball()` Python

UltraKarel

UltraKarel Commands

paint(color)Python

UltraKarel Conditions

random_chance()Python

color_is(color)Python

Color

# Paints a square red.
paint(color['red'])


# Colors:
color['red']
color['blue']
color['green']
color['yellow']
color['cyan']
color['orange']
color['white']
color['black']
color['gray']
color['purple']


# Creates a color using a color string
# Syntax: paint('color_string')
paint('cyan')


# Color Strings:
'red'
'blue'
'green'
'yellow'
'cyan'
'orange'
'white'
'black'
'gray'
'purple'


# Creates a color using an RGB value to paint
# Syntax: paint('rgb(red_value, green_value, blue_value)')
paint('rgb(130, 50, 32)')


# Creates a color using a Hex color code string
# Syntax: paint(hex_color_string)
paint('#63c151')


# Determine if a square is a certain color
if color_is(color['red']):
    move()
        Python

Random

# Returns true 50% of the time
random_chance()
# Returns true probability percentage of the time
random_chance(probability)
# Returns true 20% of the time.
random_chance(0.2)
# Example
if random_chance(0.8):
        put_ball()
Python

Functions

Writing a Function

Writing a function is like teaching karel a new word.

Naming Functions: You can name your functions whatever you want, but you can't have spaces in the function name.

Remember that commands in functions must be indented one level

def turn_right():
    turn_left()
    turn_left()
    turn_left()

def turn_around():
    turn_left()
    turn_left()

def your_function_name():
  # Code that will run when you make a call to
  # this function.Python

Calling a Function

You call a function to tell the computer to actually carry out the new command.

# Call the turnn_around() function once
turn_around()

# Call the turn_right() function 2 times
turn_right()
turn_right()Python

Conditional Statements

Remember that comands in conditional statements must be indented one level.

If statements

if condition:
    #code that will run if the condition is truePython

If/Else statements

if condition:
    #code that will run if the condition is true
else:
    #code that will run if condition is not truePython

Example of if statements

if front_is_clear():
  move()

if balls_present():
  take_ball()
else:
  move()Python

Karel Conditions

Don't forget the () at the end!

front_is_clear()
left_is_clear()
right_is_clear()

facing_north()
facing_south()
facing_east()
facing_west()

balls_present()
            Python

front_is_blocked()
left_is_blocked()
right_is_blocked()

not_facing_north()
not_facing_south()
not_facing_east()
not_facing_west()

no_balls_present()
            Python

Loops

Remember that commands in a loop statement must be indented one level.

While Loops

while CONDITION:
  # Code that will run while the CONDITION is true.
  # Once the CONDITION is no longer true,
  # it will stop.Python

Example of while loops

# This moves Karel to a wall
while front_is_clear():
    move()Python

For Loops

for i in range(COUNT):
  # Code that will run 'COUNT' timesPython

Example of for loops

# This puts down 10 balls */
for i in range(10):
    put_ball()Python

You can have multiple statements or function calls in a for loop.

# This puts down five balls and moves after each one
for i in range(5):
    put_ball()
    move()Python

Use for-loops when you want to repeat something a fixed number of times.

Use while-loops when you want to repeat something as long as a condition is true.

Comments

"""
A multi-line comment describes your code
to someone who is reading it.
"""

# Use single line comments to clarify code.Python

Autograder Results

Your Output

Solution Output

Errors:

Ending World

Karel's Built in Commands

Karel Commands

UltraKarel

UltraKarel Commands

UltraKarel Conditions

Color

Random

Functions

Writing a Function

Calling a Function

You call a function to tell the computer to actually carry out the new command.

Conditional Statements

If statements

If/Else statements

Example of if statements

Karel Conditions

Loops

While Loops

Example of while loops

For Loops

Example of for loops

Comments

Comments

Products

Computer Science Curriculum

Customizable K-12 Computer Science Curriculum

Example 14 If Statements Example

Error: Line -1

Autograder Results

Your Output

Solution Output

Errors:

Ending World

Karel's Built in Commands

Karel Commands

UltraKarel

UltraKarel Commands

UltraKarel Conditions

Color

Random

Functions

Writing a Function

Calling a Function

You call a function to tell the computer to actually carry out the new command.

Conditional Statements

If statements

If/Else statements

Example of if statements

Karel Conditions

Loops

While Loops

Example of while loops

For Loops

Example of for loops

Comments

Comments