Intro to Python for Non-Programmers

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Intro to Python for Non-Programmers Ahmad Alhour / Team Lead, TrustYou 23 April, 2019

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Overview ● A very basic intro to programming ● Intended for people who have no clue about it ● Mainly, to give you a taste of what it is about ● Hopefully, it’ll put you on the right track to study on your own 3 aalhour.com

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Hello! I am Ahmad I have been doing programming as a hobby since I was a kid, and professionally since 2008. I also have a B.Sc. degree in Computer Science. At TrustYou, I lead several projects, all powered by Python! 4

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15 mins Intro and Setting Expectations 30 mins What is Programming? 10 mins Intro to REPL.it 45 mins Numbers, Variables and Strings 30 mins Functions (Part 1) Plan Until Lunch

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15 mins Recap and Review 45 mins Conditionals 45 mins While Loops and Collections 45 mins For Loops and Functions (Part 2) 30 mins Wrapping Up Plan After Lunch

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1. What Are Your Expectations? 7 aalhour.com

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“ “Blessed is he who expects nothing, for he shall never be disappointed.” ― Alexander Pope 8 aalhour.com

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Group Exercise: Let’s Set Expectations Together ● Learn the basics of Programming ● Learn the basics of Python ● There will be no installation 9 aalhour.com

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2. What is Programming? 10 aalhour.com

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12 Programming 101 ● Is a way of telling the computer how to do certain things by giving it a set of instructions ● These instructions are called Programs ● Everything that a computer does, is done using a computer program aalhour.com

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Example Programs 13 aalhour.com

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3. What is a Programmer? 14 aalhour.com

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15 What is a Programmer? “A programmer is an Earthling who can turn big amounts of caﬀeine and pizza into code!” ― Anonymous aalhour.com

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17 Seriously, what is a programmer? ● A person who writes instructions is a computer programmer ● These instructions come in diﬀerent languages ● These languages are called computer languages aalhour.com

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4. What is a Programming Language? 18 aalhour.com

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19 What is a Programming Language? ● A programming language is a type of written language that tells computers what to do ● They are used to make all the computer programs ● A P.L. is like a set of instructions that the computer follows to do something aalhour.com

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20 Machine Language ● The computer’s native language ● The set of instructions have to be coded in 1s and 0s in order for the computer to follow them ● Writing programs in binary (1s and 0s) is tedious ● Lowest level language aalhour.com

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21 High-level Languages ● Programming languages that are closer to English than Machine code ● Human-readable ● Expresses more by writing less aalhour.com

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5. Example Programs 22 aalhour.com

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23 Displaying “Hello, World!” in Machine Code 0110100001100101011011 0001101100011011110010 0000011101110110111101 1100100110110001100100

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24 Displaying “Hello, World!” in Assembly global _main extern _GetStdHandle@4 extern _WriteFile@20 extern _ExitProcess@4 section .text _main: ; DWORD bytes; mov ebp, esp sub esp, 4 ; hStdOut = GetstdHandle( STD_OUTPUT_HANDLE) push -11 call _GetStdHandle@4 mov ebx, eax ; WriteFile( hstdOut, message, length(message), &bytes, 0); push 0 lea eax, [ebp-4] push eax push (message_end - message) push message push ebx call _WriteFile@20 ; ExitProcess(0) push 0 call _ExitProcess@4 ; never here hlt message: db 'Hello, World', 10 message_end:

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25 #include int main(void) { printf("Hello, World!\n"); return 0; } Displaying “Hello, World!” in C

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26 print(“Hello, World!”) Displaying “Hello, World!” in Python

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6. Enter: Python! 27 aalhour.com

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29 The Python Programming Language ● High-level programming language ● Named after BBC’s "Monty Python’s Flying Circus" show ● One of the most adopted languages world-wide ● Most TY products are powered by it aalhour.com

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30 numbers = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] for each_number in numbers: print(each_number) Example Python Program: Counting to 10

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Let’s take a break!

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7. Let’s REPL.IT 32 aalhour.com

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33 Demo Time! ● General walk through REPL.IT aalhour.com

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8. Hello, World! Your First Python Program 34 aalhour.com

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35 Numbers in Python ● Create a new repl on REPL.IT ● Type in the main.py tab: print(“hello, world!”) ● Click on run >! aalhour.com

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9. Numbers The Art of Calculating Stuﬀ 36 aalhour.com

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37 Numbers in Python ● One of value types ● Demo: ○ Numbers in interactive mode ○ Basic arithmetic aalhour.com

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38 Evaluation Order of Operations ● First, “*” and “/” are evaluated ● Then, “-” and “+” are evaluated ● All operations are evaluated left-to-right aalhour.com

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39 Guess the result of the following: ● 9 * 9 - 9 * 10 / 15 ● 1 + 1 + 1 * 2 + 6 / 2 ● 10 + 1 * 2 - 4 / 20 ● 50 - 5 - 5 - 10 / 2 ● 1 + 2 - 5 * 3 - 7 + 4 * 9 / 12 aalhour.com

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40 Grouping Calculations with Parentheses ● Used for separating calculations into distinct groups ● For example: ○ (10 * 2) + (5 - 3) / (4 + 2) ○ → 20 + 2 / 6 ○ → 20 + 0.333 ○ → 20.333 aalhour.com

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41 Evaluation Order of Operations: Revisited! ● First, what is in “(” and “)” is evaluated ● Then, “*” and “/” are evaluated ● Then, “-” and “+” are evaluated ● All operations are evaluated left-to-right aalhour.com

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42 Guess the result of the following: ● 9 * (9 - 9) * 10 / 15 ● (1 + 1 + 1) * (2 + 6) / 2 ● 10 + 1 * (2 - 4) / 20 ● 50 - 5 - (5 - 10) / 2 ● (1 + 2) - 5 * (3 - 7 + 4) * 9 / 12 aalhour.com

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10. Variables The Art of Naming Stuﬀ 43 aalhour.com

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44 Variables in Python ● Used to give names to values ● You give names to stuﬀ to refer to them later on in your program ● You give names to stuﬀ using the “=” symbol, known as “assignment operator” ● Variable names must begin with a letter aalhour.com

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45 ● Implement one plus one operations using variables Demo Time aalhour.com

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46 Example usage: ● Calculate the average population for Earth in 2015 ● Give it a name ● Everytime you want to refer to it you just use the name rather than to recalculate it again Variables in Python aalhour.com

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47 Break the calculation down using variables: ● (10 * 2) + (5 - 3) / (4 + 2) ● X + Y / Z ● Store result in “result” name Demo Time aalhour.com

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48 Break the following calculations down into sub-calculations and store them into variables: ● 9 * (9 - 9) * 10 / 15 ● (1 + 1 + 1) * (2 + 6) / 2 ● 10 + 1 * (2 - 4) / 20 ● 50 - 5 - (5 - 10) / 2 ● (1 + 2) - 5 * (3 - 7 + 4) * 9 / 12 Exercise aalhour.com

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11. Strings The Art of Texting Stuﬀ 49 aalhour.com

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50 ● Used to represent text in Python ● Examples: ○ “Hello, World!” ○ “My name is Ahmad.” ○ “Bier und Brezel.” ● Any text in between “” is a string in Python Strings in Python aalhour.com

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51 ● Type in the following strings in the interactive shell: ○ “Hello, World!” ○ “My name is Ahmad.” ○ “Bier und Brezel.” ● Use all of the above with print ● Store all of the above in variables and then print them Demo Time aalhour.com

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52 Print the following poem: Doubt thou the stars are ﬁre; Doubt that the sun doth move; Doubt truth to be a liar; But never doubt I love. ― William Shakespeare, Hamlet Exercise aalhour.com

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Let’s take a break!

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54 12. Functions The Art of Naming Computations aalhour.com

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55 ● Just like how variables give name to values, functions give name to calculations/instructions ● It is easier to refer to a group of instructions with a name than write them all over again ● You need three main words to deﬁne functions: “def”, “” and “return” Functions in Python aalhour.com

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56 ● You know functions already! ● Print is a Python function that takes whatever value you’d like and prints it on the screen ● Print can take several values separated by commas, e.g.: ○ print(“My name is:”, “Slim Shady”) ○ print(“One plus one is:”, 2) Functions in Python aalhour.com

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57 ● Deﬁne a new function ● Print William Shakespeare’s poem ● repl.it/@aalhour/WilliamShakespeare Demo Time aalhour.com

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58 ● Deﬁne a new function ● Code the one plus one example in variables ● Return the result Demo Time aalhour.com

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59 ● Deﬁne a function to calculate each of the following, with variables, and return the result: ○ 9 * (9 - 9) * 10 / 15 ○ (1 + 1 + 1) * (2 + 6) / 2 ○ 10 + 1 * (2 - 4) / 20 ○ 50 - 5 - (5 - 10) / 2 ○ (1 + 2) - 5 * (3 - 7 + 4) * 9 / 12 Exercise aalhour.com

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60 ● Functions can take values as arguments! ● Useful for doing tasks with user input, for example: ○ Given 5 numbers, return the avg. ○ Given weight and height of a person, calculate their BMI. Functions in Python aalhour.com

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61 ● Define a new function for printing different values ● Define a new function for calculating BMI given height and weight ● repl.it/@aalhour/FuncsWithVars Demo Time aalhour.com

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62 ● Define a function that accepts two arguments and returns the result of their addition ● Define a function that takes five arguments and returns the average Exercise aalhour.com

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Lunch Break See you in an hour!

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15 mins Recap and Review 45 mins Conditionals 45 mins While Loops and Collections 45 mins For Loops and Functions (again!) 30 mins Wrapping Up Plan After Lunch

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13. Recap What Have We Learned So Far? 65 aalhour.com

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66 ● Numbers: 1, 2, 3 ● Order of operations: (, ), *, /, +, - ● Strings: “Hi!” ● Variables: x = 1 ● Functions: def greet(): print(“Hello, world!”) Recap aalhour.com

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14. Conditionals The Art of Comparing Stuﬀ 67 aalhour.com

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68 ● They are the Yes/No questions of programming ● The answer is either a True or a False ● These values are called Booleans ● Conditionals compare values together ● Using simple operators such as: ○ >, <, >=, <= and == Conditionals aalhour.com

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69 Compare several numbers together and check the results: ● 1 < 10 ● 1 <= 10 ● 5 > 2 ● 5 >= 2 ● 1 == 1 ● 0 <= 0 Demo Time aalhour.com

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70 Evaluate the following in your mind and then on REPL.IT: ● 1 + 1 + 1 + 1 + 1 > 4 ● 2 * 2 < 5 / 3 ● 5 * 3 >= 15 ● 10 / 2 == 5 ● (25 * 3) - 100 / 2 < (25 * 2) + 1 Exercise aalhour.com

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71 ● First, what is in “(” and “)” is evaluated ● Then, “*” and “/” are evaluated ● Then, “-” and “+” are evaluated ● Lastly, comparisons are evaluated ○ “>”, “>=”, “<”, “<=”, “==” ● Operations get evaluated left-to-right Evaluation Order of Operations: Expanded aalhour.com

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72 ● A Python statement for making decisions based on a condition ● In a nutshell: if this, then that ● For example: If your age is greater than 18, then you are allowed to enter the bar The If Statement aalhour.com

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73 ● If old enough to enter bar, print “proceed to bar!”. ● If not old enough to enter bar, print “too young still!” Demo Time aalhour.com

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74 Teenager Exercise 01: Deﬁne an “age” variable and insert your age. Write an if statement to display “teenager” if age is less than 21 Exercises aalhour.com

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75 Exercises Positive Number 01: Deﬁne a “number” variable and insert a random value. Write an if statement to display “positive” if the number is greater than 0 aalhour.com

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76 ● Expanded If-Statement for handling cases that don’t match the condition. ● In a nutshell: if this, then that; otherwise, something else ● For example: ○ If your age is greater than 18, then you are allowed to enter the bar; otherwise, you are asked to leave The If-Else Statement aalhour.com

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77 Translate the following into Python: If old enough to enter bar then print “proceed to bar!” else print “please, leave!” Demo Time aalhour.com

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78 ● Teenager Exercise 02: Expand the code and add an else block which prints “adult” if the teenager check is not met ● Positive Number 02: Expand the code and add an else block which prints “negative” if the positive check is not met Exercises aalhour.com

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79 ● Teenager Exercise 03: Wrap the exercise’s code in a function that accepts an “age” argument and returns nothing. ● Positive Number 03: Wrap the exercise’s code in a function that accepts a “number” argument and returns nothing. Exercises aalhour.com

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Let’s take a break!

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15. While Loops The Art of Repeating Stuﬀ 81 aalhour.com

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82 ● Loops are good for repeating instructions for a number of times ● They’re good because we don’t have to duplicate code, but we just tell the program to keep repeating stuﬀ ● Loops repeat stuﬀ according to a condition as well While Loops aalhour.com

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83 ● Example: ○ While my BMI is above 100, keep working out! ○ While my coﬀee is not empty, keep writing code! ● You need two words to loop stuﬀ: ○ “while” and “break” ○ Break is used to stop looping or else you will loop forever! While Loops aalhour.com

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84 while True: print(1) # Prints 1 forever while 1 == 1: print(1) # Prints 1 forever while 5 > 2: print(1) # Prints 1 forever Code Examples aalhour.com

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85 # Prints 1 once, then stops while True: print(1) break # Prints 1 once, then stops while 1 == 1: print(1) break Code Examples aalhour.com

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86 ● Print “Hello, World!” forever! ● Print your own name forever! ● Calculate the following formula and print the result forever: ○ 10 * 312 / 57 + 23 * 5 + 823 / 74 Play Time aalhour.com

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87 ● To avoid running forever, we need to maintain a counter and a limit ● Counters are variables that keep track of how many times a loop ran ● Limits allow us to break out of the loop once the loop runs for a max. number of times Counters and Limits aalhour.com

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88 counter = 1 while counter < 10: print(counter) counter = counter + 1 Code Example aalhour.com

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89 ● Add a counter number and increment it inside the loop. Print the counter to show that its value changes. ● Add a limit check before the work with a break. Demo Time aalhour.com

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90 ● Print numbers from 0 until 1 million ● Teenager Exercise 04: Deﬁne age variable and assign it to 1. Run the loop with the teenager check. The loop should print the age and then increment it until the age is no longer teeanger, after which the loop should terminate Exercises aalhour.com

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91 ● You can ask for the user’s input using the built-in “input” function ● For example: input(“Enter a number:”) ● Useful for asking the user for data. User Input aalhour.com

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92 ● Ask the user for their name and then print it out. ● Ask the user for their age and print it out with the statement: “Your age is:” Demo Time aalhour.com

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93 Teenager Exercise 05: Ask the user for their age. Run the loop with the teenager check on the user input. The loop should print “You are still a teenager” alongside the age and then increment it until the age is no longer teeanger, after which the loop should terminate. Exercises aalhour.com

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94 Teenager Exercise 06: Wrap the Teenager Exercise #05 with a function that asks the user for their age and then prints out the message: “You are still a teenager:” alongside their age. Increments the age number until the loop no longer runs. Exercises aalhour.com

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Let’s take a break!

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16. Collections The Art of Grouping Stuﬀ 96 aalhour.com

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97 ● Collections are a way of keeping items together, e.g.: bags! ● We will take a look at lists in Python ● Lists are good for memorizing the order in which we keep things too Collections aalhour.com

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98 A list of numbers: [1, 2, 3, 4, 5] A list of strings: [“Alice”, “Bob”, “Claire”] A mixed list of things: [123, “Ahmad”, message] Examples of Collections aalhour.com

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99 Anything in between “[” and “]” is considered a list A list can contain anything in Python: ● Numbers ● Strings ● Variables ● Other lists How can I create a collection? aalhour.com

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100 ● Create a list of the English alphabet ● Create a list that contains your: ○ ﬁrst name ○ last name ○ your lucky number ○ your current address ● Print the above lists using the print() function Exercises aalhour.com

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101 ● Ranges in Python are useful functions for generating collections of numbers ● More like a shortcut ● Easy to use ● Example: ○ range(1, 10): generates a collection of all numbers from 1 until 9 (stops at 10 but doesn’t include it) Ranges aalhour.com

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102 ● range() takes three arguments: ○ Start: number to start with ○ End: number to stop at ○ Step: increment size ● Examples: ○ range(0, 5, 1) → [0,1,2,3,4,5] ○ range(0, 6, 2) → [0, 2, 4] ○ range(0, 6, 3) → [0, 3] Ranges: In Detail aalhour.com

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103 ● start = 0 by default, unless specified ● step = 1 by default, unless specified ● end is mandatory and must be always specified ● Examples: ○ range(6) → [0,1,2,3,4,5] ■ Same as: range(0, 6, 1) Ranges: Default Behavior aalhour.com

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104 ● Generate a list of all odd numbers greater than 0 and less than 1000 ● Generate a list of all even numbers greater than 29 and less than 250 ● Generate a list of all numbers less than -1 and greater than -132 ● Generate a list of all even numbers less than -250 and greater than -277 Exercises aalhour.com

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Let’s take a break!

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17. For Loops The Art of Iterating Over Collections 106 aalhour.com

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107 ● For loops are another way to apply the same computation more than once according to a check in your program ● Similar to While Loops but easier to maintain ○ No need for a counter ○ No need for a beaking check For Loops aalhour.com

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108 For loops need a collection in order to… well, loop! :P Example: for every item in shopping cart, print it out on the screen: for item in [“Shoes”, “Tablet”]: print(item) For Loops aalhour.com

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109 for number in [1, 2, 3, 4, 5]: print(number) for number in range(6): print(number) for person in [“AA”, “AM”, “DW”, “DV”]: print(person) For Loops: Examples aalhour.com

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110 ● Syntax: ○ for in : ■ List of commands ● The variable name can be whatever you want ● The collection can have whatever you want but it must be a collection, not anything else How do I make a for loop? aalhour.com

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111 1. For every item in the collection: a. Assign the item to the variable name that the programmer wrote b. Enter the block c. Execute all commands d. Go to 1 and grab the next the item 2. If the collection is empty or has no more items to see, then exit the block How do for loops work? aalhour.com

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112 for number in [1, 2, 3, 4, 5]: print(number) Loop execution log: number = 1 → print(1) number = 2 → print(2) number = 3 → print(3) number = 4 → print(4) number = 5 → print(5) Demo aalhour.com

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113 ● Using range() and a for loop: ○ Print your name 25 times ○ Print “Hello, World!” 10 times Play time! aalhour.com

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114 Teenager Exercise 01: Reloaded Ask the user for their age. Check if the user is a teenager. Run a for loop over a range of ages until an age value that is not a teenage number anymore. Run a for loop and display the “you’re a teenager” message according to the list of ages (range) Exercises aalhour.com

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115 Teenager Exercise 02: Reloaded Wrap your solution for the “Teenager Exercise 01: Reloaded” exercise with a function that asks the user for their age and then prints out the message: “You are still a teenager:” alongside their age. Exercises aalhour.com

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Let’s take a break!

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18. Functions: Reloaded The Art of Naming Computations 117 aalhour.com

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118 Let’s solve the FizzBuzz challenge! Functions: Reloaded aalhour.com

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17. Wrapping Up 119 aalhour.com

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120 ● Numbers: 1, 2, 3 ● Order of operations: (, ), *, /, +, -, <, >, >=, <=, == ● Strings: “Hi!” ● Variables: x = 1 ● Functions: def greet(person): print(“Hello, ”, person) ● Conditionals: 1 >= 10 What You’ve Learned So Far aalhour.com

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121 ● While Loops: while True: greet(“Ahmad”) ● Lists: [1, 2, 3, “Alice”, “Bob”] ● Ranges: range(10) → [1, 2, 3, …, 9] ● For Loops: for number in range(10): print(number) What You’ve Learned So Far aalhour.com

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18. Resources for Further Study 122 aalhour.com

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123 Online Courses ● Intro to Python - by Udacity ○ https:/ /bit.ly/2N45h6F ○ 5 weeks long. Completely FREE. ● Intro to Python: Absolute Beginner - by edX ○ https:/ /bit.ly/2NJg2MW ○ 5 weeks. Completely FREE. ● Python for Everybody - by Coursera ○ https:/ /bit.ly/1KSzsbb ○ 7 weeks long. Only ﬁrst seven days are free. Resources for Further Study aalhour.com

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124 Resources for Further Study Interactive Learning ● Codecademy - Learn by Coding ○ https:/ /www.codecademy.com ○ Completely Free. Books ● Think Python, 2nd edition ○ http:/ /greenteapress.com/thinkpython2 ○ Completely Free Online. aalhour.com

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Thanks! Any questions? 125 Find me at: aalhour.com github.com/aalhour twitter.com/ahmad_alhour aalhour.com