Module 1: Programming Foundations of

WELCOME TO GAGENERAL ASSEMBLY

Foundations of Programming

Module 1:

Modules of this course

Module 1: Foundations of Programming

Module 6:EDA with Pandas

Module 2: Introduction to

Python

Module 3: Python Data Structures

Module 5:Introduction to

Pandas

Module 4: Intermediate

Python

“Computer Programming

The process of designing and building an executable computer program to accomplish a specific computing result or to perform a specific task.

Module 1: Lesson Objectives

● Describe the skills that are involved in computational thinking● Understand the four components of computational thinking

○ Decomposition○ Pattern Recognition○ Abstraction○ Algorithms

● Write basic programs to solve problems using the concept of computational thinking

Foundations of Programming

Computational Thinking

● Decomposition○ breaking down a complex problem or system

into smaller, more manageable parts● Abstraction

○ focusing on the important information only, ignoring irrelevant detail

● Pattern Recognition○ looking for similarities among and within

problems● Algorithms

○ developing a step-by-step solution to the problem, or the rules to follow to solve the problem

Karel the Robot

Talk with Karel in Python language to learn the Introduction to Python

Karel is a very simple robot living in a very simple world.

Karel in 2D world

Instructions for Karel

move() Asks Karel to move forward one block. If there is a wall, Karel will be crash and turn off.

turn_left() Ask Karel to rotate 90 degrees to the left (counterclockwise).

put_beeper() Put down a beeper from the current square. (There must be at least one beeper

in bag, otherwise it will turn off.)

pick_beeper() Pick up a beeper from the current square. (There must be a beeper at Karel's

current location, otherwise it will turn off.)

Our First Program

move()pick_beeper()turn_left()move()turn_left()move()put_beeper()

Our First Program

Quick Review: Programming Principles

● Programming is the process of creating a set of instructions with computer programming languages to tell a computer how to perform a task.

○ what the purpose is○ how to arrange it to achieve the goal

Computational Thinking:

Function

Karel moves a beeper to a ledge

Solution

def main(): move() pick_beeper() move() turn_left() move() turn_left() turn_left() turn_left() move() move() put_beeper() move()

Solution

def main(): move() pick_beeper() move() turn_left() move() turn_left() turn_left() turn_left() move() move() put_beeper() move()

Turn right

“Function

A function is a group of statements that together perform a task.

Defining a Function

def main(): move() pick_beeper() move() turn_left() move() turn_right() move() move() put_beeper() move()

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

Create Indentation by using TAB key

Don’t forget colon : and parentheses ()

Otherwise, you’ll encounter a

SyntaxError: invalid syntax

Keywords

function header

Keywords

function header

function definition

code block

Keywords

function definition

The main function calls turn_right function

function header

Quick Review: Function

● Function is a combining many instructions into a single function call to solve subproblems.

● Function definition includes:○ function header○ code block

function definition

code block

function header

indentation

Decomposition

Karel repairs the road

Solution

def main(): move()

turn_right()move()put_beeper()turn_right()turn_right()move()turn_right()move()move()move()...

“Decomposition

breaking a large problem into smaller pieces

Decomposition

def main(): jump_in() put_beeper() jump_out() move() move() jump_in() put_beeper() jump_out()

Decomposition

def main(): jump_in() put_beeper() jump_out() move() move() jump_in() put_beeper() jump_out()

Decomposition

def main(): fill_hole() move() move() fill_hole()

Precondition = standing in front of the hole

Postcondition = the hole is behind Karel

“Subroutine

subprogram that may be repeatedly called

fill_hole() subroutine

def fill_hole(): jump_in() put_beeper() jump_out()

def jump_in(): move() turn_right() move()

def jump_out(): turn_around() move() turn_right() move()

def jump_in(): move() turn_right() move()

def jump_out(): turn_around() move() turn_right() move()

def fill_hole(): move_L() put_beeper() turn_around() move_L()

def move_L(): move() turn_right() move()

def fill_hole(): move_L() put_beeper() turn_around() move_L()

def move_L(): move() turn_right() move()

def turn_around(): turn_left() turn_left()

Quick Review: Decomposition

● Decomposition - The process of breaking a program down into smaller pieces by writing subroutines.

● Decomposition is the main process of programming because it makes easier to tackle and the code is easier to read and understand.

● Decomposition should be the first process of programming.

Control Flow: For loop

“Control Flow

is the order in which instructions, statements and function calls being executed or evaluated when a program is running.

For loop: know how many times the loop should run

def turn_around(): turn_left() turn_left()

def turn_around(): for i in range(2): turn_left()

For loop - Syntax

for i in range(number of loops): First instruction Second loop instruction

What does program do?

def main(): move() for i in range(15): put_beeper() move()

move()

put_beeper()move()put_beeper()move()put_beeper()move()put_beeper()move()put_beeper()move()

move()

put_beeper()put_beeper()put_beeper()put_beeper()put_beeper()move()move()move()move()move()

Quick Review: Control Flow (For loop)

● Uses a for loop when you know how many times the loop should run

● Executes a sequence of statements in each code block

For loop - Syntax

for i in range(number of loops): First loop command Second loop command

Control Flow: While loop

Put Beepers inside except left and right corner

While loop - repeat as long as a given condition is TRUE

● for loop - know how many times to repeat● while loop - repeat as long as a given condition is TRUE

While loop demo

def main(): move_to_wall()

def move_to_wall(): while front_is_clear(): move()

While loop syntax

while loop - Syntax

while (condition that is True/False): First instruction Second instruction

For loop - Syntax

for i in range(number of loops): First instruction Second instruction

“Boolean

True or False values

Karel's Booleans

Test Opposite What it checks

front_is_clear() front_is_blocked() Is there no wall in front of Karel?

beepers_present() no_beepers_present() Is there a beeper where Karel is standing?

left_is_clear() left_is_blocked() Is there no wall to Karel’s left?

right_is_clear() right_is_blocked() Is there no wall to Karel’s right?

beepers_in_bag() no_beepers_in_bag() Is there a beeper in Karel bag?

facing_north() not_facing_north() Is Karel facing north?

facing_south() not_facing_south() Is Karel facing south?

facing_east() not_facing_east() Is Karel facing east?

facing_west() not_facing_west() Is Karel facing west?

While loop syntax

while loop - Syntax

while boolean: First instruction Second instruction

For loop - Syntax

for i in range(number of loops): First instruction Second instruction

Put beepers inside except left and right corner

def main(): move() while front_is_clear(): put_beeper() move()

Abstraction

def main(): move() while front_is_clear(): put_beeper() move() front_is

_clear?

put_beeper()

move()

“Abstraction

focusing on the important information only, ignoring irrelevant detail

Quick Review: Control Flow (While loop)

● while loop - Syntax

instruction 1while boolean: instruction2 instruction 3instruction 4

instruction 2

instruction 3

instruction4

instruction 1

Control Flow: If-Statement

What happens if Karel is moved forward?

● Check before run

beeper_line2_crash.py

if Diagram

def safe_move():if front_is_clear():

move() front_is_clear?

move()

beeper_line3_safemove.py

while vs if

instruction 1while boolean: instruction 2 instruction 3instruction 4 True?

instruction 2

instruction 3

instruction 4

instruction 1

while vs if

instruction 1while if boolean: instruction 2 instruction 3instruction 4 True?

instruction 2

instruction 3

instruction 4

instruction 1

Invert beepers demo

if-else

def invert_beeper(): if beepers_present(): pick_beeper() else: put_beeper() beepers_

present?

pick_beeper()

put_beeper()

Quick Review: If-statement

● Control flow has three types: for, while, if● if choose to run code block inside? but not repeat● if-else choose to run which code block but not repeat

Boolean Logic

Problem: Remove barrier (pick beepers)

How to solve?

def main(): for i in range(4): remove_fence()

def remove_fence(): pass

How to solve?

def remove_fence(): while left_is_blocked(): if beepers_present(): pick_beeper() move()

fence_karel.py

OR operator

def remove_fence(): while left_is_blocked() or beepers_present(): if beepers_present(): pick_beeper() move() turn_left() move()

boolean logic: OR operation

is_left_blocked() beepers_present()is_left_blocked() orbeepers_present()

True True True

True False True

False True True

False False False

boolean logic: AND operation

is_left_blocked() beepers_present()is_left_blocked() andbeepers_present()

True True True

True False False

False True False

False False False

Quick Review: Boolean Logic

● Booleans represent one of two values: True or False● Booleans can be used with boolean operators such as AND, OR● Use Booleans in programming to make comparisons and to determine the flow of

control in a given program.

Solving a Programming Problem

How to do when face difficult problems

● Put Beepers all over the mountains● There is a beeper at the foothill● Mountains come in many sizes.● Have any number of mountains● The world can be any size● Karel starts with lower left corner and end with

lower right corner

Problem: Climbing Mountains

Top-down strategy (Top to bottom, Big to small)

1. Write pseudocode and plan all of the functions 2. Write and test each function

a. If it has loop, you will test code block inside the loop first3. Test overall program

“Pseudocode

is an informal way of programming description that does not require any strict programming language syntax or underlying technology

Pseudocode

while the front is clear Move until find foothill If find beeper

Jump across and put beeper

Pseudocode

while the front is clear Move until find foothill If a beeper is found

Jump across and put beeper

def main(): while front_is_clear(): move_to_foothill() if beepers_present(): jump_across()

Top-down strategy (Top to bottom, Big to small)

1. Write pseudocode and plan all of the functions 2. Write and test each function

a. If it has loop, you will test code block inside the loop first3. Test overall program

Manage function in loop first

def main(): while front_is_clear(): move_to_foothill() if beepers_present(): jump_across()

def main(): move_to_foothill()

hurdle_karel.py

Quick Review: Top-down strategy (Top to bottom, Big to small)

● Write pseudocode and plan all of the functions● Write and test each function

○ If it has loop, you will test code block inside the loop first● Test overall program

Module Summary

We’ve learned:● Computational thinking

○ decomposition - breaking down a complex problem or system into smaller, more manageable parts

○ pattern recognition – looking for similarities among and within problems○ abstraction – focusing on the important information only, ignoring irrelevant

detail○ algorithms - developing a step-by-step solution to the problem, or the rules to

follow to solve the problem● Python’s control flow - if, for, while● Boolean logic● Top-down strategy

THANK YOU!

See you next time!

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