Category: Learn programming, 2 beginner

Musical Intro

Introduction

In programming, if statements help in decision-making by performing different actions based on different inputs.

Now you need to make a choice, how you want to learn it:

1. You can use AI to teach you about the different operators. Then you can learn, by your own exploration and in any programming language (scroll down to Using AI)
2. You can use the result I got, from using AI. Then you can rely on my experience to filter it.(keep on reading)
3. You can also do both in any order :-)

Single-line if Statements

Single-line if statements provide a concise way to execute a single action based on a condition. They are particularly useful when you want to simplify your code for simple condition checks.

It is written in Python, but you can use AI to translate it to other languages.

# Given a temperature value and dayIsHot is set
temperature = 26
dayIsHot = False

# When checking if the temperature is above 25 degrees
if temperature > 25: 
    dayIsHot = True  # Note: Python boolean should be 'True' with uppercase 'T'

# Then, print and assert that the day is hot
print(f"Day is hot? {dayIsHot}")
assert dayIsHot == True

The result will be:

and when we change the temperature to 25:

# given a number
number = 10
isLarger = False

# when checking if the number is larger than 9
# <write your code here>

# then the output should state that the number is larger than 9
print(f"number is larger than 9? {isLarger}")
assert isLarger== True

# given a number
number = 10
isLarger = False

# when checking if the number is larger than 9
if(number > 9): isLarger = True

# then the output should state that the number is larger than 9
print(f"number is larger than 9? {isLarger}")
assert isLarger== True

Nested if statements

In Python, “nested if statements” refer to the practice of placing one if statement inside another. This allows for more complex decision-making processes by checking for further conditions after a previous condition has already been met.

x=11
y=10

if x > 10:
    if y > 10:
        print("Both x and y are greater than 10")
    else:
        print("x is greater than 10, but y is not")
else:
    print("x is not greater than 10")

# Given variables 'temperature' and 'weatherCondition'
temperature = 31
weatherCondition = "Sunny"
result = "not yet set"

# When 'temperature' is above 30 degrees and 'weather_condition' is 'Sunny'
# <write your code here>

# Then output must be "It's a hot sunny day."
print(f"{result}")

# set the temperature to 30 and weatherCondition to "Sunny" to see a different result
# set the temperature to 31 and weatherCondition to "Rainy" to see a 3rd result
# set the temperature to 30 and weatherCondition to "Rainy" to see a 4th result

# Given variables 'temperature' and 'weatherCondition'
temperature = 31
weatherCondition = "Sunny"
result = "not yet set"

# When 'temperature' is above 30 degrees and 'weather_condition' is 'Sunny'
if temperature>30:
    if weatherCondition=="Sunny":
      result = "It's a hot sunny day."
    else:
      result = "It's a hot rainy day."
else:
    if weatherCondition=="Sunny":
      result = "It's a cold sunny day."
    else:
      result = "It's a cold rainy day."

# Then output must be "It's a hot sunny day."
print(f"{result}")

# set the temperature to 30 and weatherCondition to "Sunny" to see a different result
# set the temperature to 31 and weatherCondition to "Rainy" to see a 3rd result
# set the temperature to 30 and weatherCondition to "Rainy" to see a 4th result

if statements with logical operators

In Python, “if statements with logical operators” refer to using if statements combined with logical operators (and, or, not) to test multiple conditions at once. For example:

x = 2
if x >= 1 and x <= 9:
    print("x is between 1 and 9")
else:
    print("x is below 1 or above 9")

And the result will be:

“and” means both statements need to be true.

x=2

# the following statement:
if x>=1 and x<=9:
    print("x is between 1 and 9")

# could be written as:
if x>=1:
    if x<=9:
    print("x is between 1 and 9")

“or” means one of the statements need to be true.

x=3

# the following statement:
if x==1 or x==3:
    print("x is either 1 or 3")

# could be written as:
if x==1:
    print("x is either 1 or 3")
if x==3:
    print("x is either 1 or 3")

# Given variables 'temperature' and 'weatherCondition'
temperature = 31
weatherCondition = "Sunny"
result = "not yet set"

# When 'temperature' is above 30 degrees and 'weather_condition' is 'Sunny'
# <write your code here>

# Then output must be "It's a hot sunny day."
print(f"{result}")
assert result == "It's a hot sunny day."

# Given variables 'temperature' and 'weatherCondition'
temperature = 31
weatherCondition = "Sunny"
result = "not yet set"

# When 'temperature' is above 30 degrees and 'weather_condition' is 'Sunny'
if temperature>30 and weatherCondition == "Sunny":
	result = "It's a hot sunny day."

# Then output must be "It's a hot sunny day."
print(f"{result}")
assert result == "It's a hot sunny day."

if-else one-liner (Ternary Operator)

This operator is typically used to assign a value to a variable based on a condition.

# if you change the score value to 75, then you will get a different result.
score = 76

result = "High" if score > 75 else "Low"

print(result)
assert result == "High"

# Given a variable 'age' 'adult' are set to 18 and None
age = 18
adult = None

# When determining if the age qualifies someone as an adult
# <write you code here>

# Then print the age and adult result, and assert the adult result
print(f"age: {age}, adult: {adult}")
assert adult == True

# Given a variable 'age' 'adult' are set to 18 and None
age = 18
adult = None

# When determining if the age qualifies someone as an adult
adult = True if age>=18 else False

# Then print the age and adult result, and assert the adult result
print(f"age: {age}, adult: {adult}")
assert adult == True

Pass statement

In Python, the pass statement is a null operation — when it is executed, nothing happens. It is often used as a placeholder to ensure the syntax of your code is correct, allowing you to maintain the structural integrity of the code while you’re still thinking about the logic or implementing it later.

x = 2

if x>1:
    pass # passholder for future code

else:
    x+=1
    

print(f"x is {x}")
assert x==2

In other programming languages, we could just have written a comment.
We can’t do that in Python, because the line after an if statement, needs to be indent, while the else can’t be it. So we need to write pass with an indent.

# Given we have a variable price with value 50
price = 50

# When the price is above 40, then we want to make a pass-statement as a placeholder for future code. Else the price must be increased by 10%
if price >40:
  # <insert your code here>
else:
  price *=1.1

# Then we print and assert the price
print(f"Price: {price}")
assert price==50

# Given we have a variable price with value 50
price = 50

# When the price is above 40, then we want to make a pass-statement as a placeholder for future code. Else the price must be increased by 10%
if price >40:
  pass
else:
  price *=1.1

# Then we print and assert the price
print(f"Price: {price}")
assert price==50

Conclusion

Today, we embarked on an enlightening journey through various Python programming constructs, those crucial components that guide the flow and decisions within our scripts.

We began by examining single-line if statements, a concise method for executing actions based on conditions. This exploration allowed us to efficiently manage simple checks within our code, reinforcing the ease of conditional programming.

Transitioning to nested if statements, we delved into the realm of complex decision-making. Here, we learned to layer conditions within one another, enhancing our ability to handle more intricate logical sequences based on multiple criteria.

We then ventured into the use of logical operators within if statements, including ‘and’, ‘or’, and ‘not’. This exploration enabled us to evaluate multiple conditions simultaneously, streamlining our code for more sophisticated decision-making processes.

To improve code conciseness and readability, we embraced the if-else ternary operator. This powerful one-liner allowed us to assign values conditionally in a single, elegant statement, further simplifying our conditional assignments.

Delving deeper, we explored the pass statement, a unique Python feature that acts as a placeholder. By using the pass statement, we maintained the structural integrity of our code during the initial stages of development, ensuring that our scripts remained syntactically correct even when specific logic was not yet implemented.

Armed with these skills, we’re better equipped to tackle a wide array of programming tasks and navigate the complex landscape of software development with confidence.

Using AI

All this have been created with the cooperation with AI.

Often it can be more useful just to learn, what is needed in the moment, than to learn everything about a topic. This is where AI is perfect.

We can use the free ChatGPT 3.5 to learn about operators. You are welcome to try other and if you do, please write a comment!

Essential prompts can be:

When we don’t know the name of what we want to learn, then we can ask AI about it:

What is an if statement in Python?

When we want to learn more about the topic

Are there other types of if-statements in Python?

You can ask the same question twice and get more results:

are there other?

Then you can explore each subject with:

I would like to learn more about "if statements with logical operators". 

Can you show me:
1. an example of how it works? (in python)
2. a real world application of it? (in python)

I want the code examples to be written with given, when, and then steps.
The then step needs to contain a print and assert (for manual and automatic verification).

To get an assignment to learn from:

I would like to learn more about "if statements with logical operators". 

Can you make a assignment for me to solve?

The assignment needs to be written in Python as comments.
Use only given, when, and then comments. No code.

And sometimes you might need to start a new session.

Sometimes the AI makes a mistake like writing Given, Then, When (wrong order) and sometimes starting a new session makes it go away.

And you can get AI to solve it for you:

Can you please solve this assignment for me in Python code?

Congratulations – Lesson complete!

Musical Intro

Introduction

In programming, operators are symbols that perform operations like mathematical calculations.

Now you need to make a choice, how you want to learn it:

1. You can use AI to teach you about the different operators. Then you can learn, by your own exploration and in any programming language (scroll down to Using AI)
2. You can use the result I got, from using AI. Then you can rely on my experience to filter it.(keep on reading)
3. You can also do both in any order :-)

Arithmetic operators: + , – , * , / , // , %

Arithmetic operators are used to perform mathematical operations on numerical values.

It is written in Python, but you can use AI to translate it to other languages.

# Given two numbers
num1 = 10
num2 = 3

# When using arithmetic operators
addition = num1 + num2
subtraction = num1 - num2
multiplication = num1 * num2
division = num1 / num2
divisionRoundDown num1 // num2
modulus = num1 % num2  # Returns the remainder of the division

# Then the results should be as expected
print(f"Addition: {addition}")
assert addition == 10+3

print(f"Subtraction: {subtraction}")
assert subtraction== 10-3

print(f"Multiplication: {multiplication}")
assert multiplication== 10*3

print(f"Division: {division}") 
assert division == 10/3 

print(f"divisionRoundDown: {divisionRoundDown}") 
assert divisionRoundDown== 10//3 # is 3.333... rounded down is 3 

print(f"Modulus: {modulus}")
assert modulus== 10%3 # 10 will be split into three 3's and 1 will remain 

The result will be:

In case you wonder over why 10/3 equals 3.3333333333333335, it is because of a floating error (lack of precision). We will go into it on a later stage.

# given we want to arrange team activities for attendies
menAttendees = 27
womenAttendees = 25
childrenAttendees = 11  
groupSize = 5

# when we calculate the number of total attendees
totalAttendees = # please fill this out

# then it must match the expected result
print(f"Total attendees: {totalAttendees}")
assert totalAttendees == 63


# when we calculate the number of groups
numbeOfGroups = # please fill this out

# then it must match the expected result
print(f"Number of groups: {numbeOfGroups}")
assert numbeOfGroups == 12


# when we calculate the number of people without a groups
attendeesWithoutAGroup = # please fill this out

# then it must match the expected result
print(f"Attendeeswithout a group: {attendeesWithoutAGroup}")
assert attendeesWithoutAGroup == 3

print("All calculations are correct!")

# when we calculate the number of total attendees
totalAttendees = menAttendees + womenAttendees + childrenAttendees 

# when we calculate the number of groups
numbeOfGroups = totalAttendees // groupSize

# when we calculate the number of people without a groups
attendeesWithoutAGroup = totalAttendees % groupSize

Assignment Operators: = (and not ==)

When we use = then we assign a value to a variable.
When we use == then we verify if something is equal or not. The result is either true or false

# When we assign three values to three variables with an =
a = 1
b = 1
c = 2

# Then we can verify the values with an ==
print(a==b)
print(a==c)

And the result will be:

# please fix the followin code, so it works
a = 1
b == 1

assert a=b
print("you did it!")

# please fix the followin code, so it works
a = 1
b = 1

assert a==b
print("you did it!")

Comparison operators: == , > , >= , <= , < , !=

We can also verify other than just equal

print("greater than >")
print(f"4>3 -> {4>3}")
print(f"3>3 -> {3>3}")

print("----")
print("greater equal than >=")
print(f"4>=3 -> {4>=3}")
print(f"3>=3 -> {3>=3}")
print(f"2>=3 -> {2>=3}")

print("----")
print("lesser equal than <=")
print(f"4<=3 -> {4<=3}")
print(f"3<=3 -> {3<=3}")
print(f"2<=3 -> {2<=3}")

print("----")
print("lesser than <")
print(f"3<3 -> {3<3}")
print(f"2<3 -> {2<3}")

print("----")
print("not equal !=")
print(f"3!=4 -> {3!=4}")
print(f"3!=3 -> {3!=3}")
print(f"4!=3 -> {4!=3}")

# please fix the followin code, so it works
assert 3>4
assert 4<4
assert 5<4
assert 5=="abc"
print("you did it!")

# please fix the followin code, so it works
assert 3<4
assert 4==4
assert 5>4
assert 5!="abc"
print("you did it!")

Compound assignment operators: += , -= , *= , /=

To make code shorter, we can use:

# When we have a number variable
number = 1
print(number)

# Then we want to increase a number by 3 we can write:
number = number + 3
print(number)
assert number == 4

# Or
number += 3
print(number)
assert number == 7

# When we have a number variable
number = 5
print(number)

# Then we want to decrease a number by 3 we can write:
number = number - 3
print(number)
assert number == 2

# Or
number -= 3
print(number)
assert number == -1

# When we have a number variable
number = 1
print(number)

# Then we want to multiply a number by 3 we can write:
number = number * 3
print(number)
assert number == 3

# Or
number *= 3
print(number)
assert number == 9

# When we have a number variable
number = 8
print(number)

# Then we want to multiply a number by 2 we can write:
number = number / 2
print(number)
assert number == 4

# Or
number /= 2
print(number)
assert number == 2

# refactor the following code to use +=, -=, *=, /=
number1 = 3

number1 = number1 + 3
number1 = number1 - 2
number1 = number1 * 3
number1 = number1 / 2

assert number1 == 6
print("you did it!")

# refactor the following code to use +=, -=, *=, /=
number1 = 3

number1 += 3
number1 -= 2
number1 *= 3
number1 /= 2

assert number1 == 6
print("you did it!")

Rounding operators: round, flour, celling

A number can be rounded to a specific decimal by using a Math library:

# given we have a number variable
number1 = 1.4999999
number2 = 1.5000000

# when we round it in multiple ways:
roundedDown = round(number1)
roundedUp = round(number2)

# then it will be rounded up or down, based on if it's half way or not.
print(f"roundedDown: {number1}->{roundedDown}")
assert roundedDown == 1

print(f"roundedUp:   {number2}->{roundedUp}")
assert roundedUp == 2

To always round down we can use math.floor():

import math

# given we have a number variable
number1 = 1.0000000
number2 = 1.9999999
number3 = 2.0000000

# when we round it in multiple ways:
floor1 = math.floor(number1)
floor2 = math.floor(number2)
floor3 = math.floor(number3)

# then it will be rounded up or down, based on if it's half way or not.
print(f" {number1}-> {floor1}")
assert floor1 == 1

print(f" {number2}-> {floor2}")
assert floor2 == 1

print(f" {number3}-> {floor3}")
assert floor3 == 2

To always round down we can use math.ceil():

import math

# given we have a number variable
number1 = 1.0000000
number2 = 1.0000001
number3 = 1.9999999

# when we round it in multiple ways:
floor1 = math.ceil(number1)
floor2 = math.ceil(number2)
floor3 = math.ceil(number3)

# then it will be rounded up or down, based on if it's half way or not.
print(f" {number1}-> {floor1}")
assert floor1 == 1

print(f" {number2}-> {floor2}")
assert floor2 == 2

print(f" {number3}-> {floor3}")
assert floor3 == 2

import math

# given you have the following numbers
number1a = # insert a correct value here
number1b = # insert a correct value here
number2a = # insert a correct value here
number2b = # insert a correct value here
number3a = # insert a correct value here
number3b = # insert a correct value here

# when you apply math.round math.floor, and math.ceil:
rounded1a = math.round(number1a)
rounded1b = math.round(number1b)
rounded2a = math.floor(number2a)
rounded2b = math.floor(number2b)
rounded3a = math.ceil(number3a)
rounded3b = math.ceil(number3b)

# then you must get the expected values
assert rounded1a == 1, f"{number1a} -> {rounded1a}"
assert rounded1b == 2, f"{number1b} -> {rounded1b}"
assert rounded2a == 3, f"{number2a} -> {rounded2a}"
assert rounded2b == 4, f"{number2b} -> {rounded2b}"
assert rounded3a == 5, f"{number3a} -> {rounded3a}"
assert rounded3b == 6, f"{number3b} -> {rounded3b}"

print("you did it!")

import math

# given you have the following numbers
number1a = 1.499999
number1b = 1.500000
number2a = 3.999999
number2b = 4.000000
number3a = 5.000000
number3b = 5.000001

# when you apply math.round math.floor, and math.ceil:
rounded1a = math.round(number1a)
rounded1b = math.round(number1b)
rounded2a = math.floor(number2a)
rounded2b = math.floor(number2b)
rounded3a = math.ceil(number3a)
rounded3b = math.ceil(number3b)

# then you must get the expected values
assert rounded1a == 1, f"{number1a} -> {rounded1a}"
assert rounded1b == 2, f"{number1b} -> {rounded1b}"
assert rounded2a == 3, f"{number2a} -> {rounded2a}"
assert rounded2b == 4, f"{number2b} -> {rounded2b}"
assert rounded3a == 5, f"{number3a} -> {rounded3a}"
assert rounded3b == 6, f"{number3b} -> {rounded3b}"

print("you did it!")

Exponentiation operators: 2³ , pow(2,3) , 2**3 , √9 , sqrt(9) , 9**.5

If we want write 3², which is 3*3 = 9
or 2³, which is 2*2*2 = 8

We can do that with math.pow()

import math

# when we user mat.pow() method
number1 = math.pow(2,3)
number2 = math.pow(3,2)

# and the ** can also be user
number3 = 2**3

# then we can see the power of the values
print(f" pow(2,3) = 2*2*2 -> {number1}")
assert number1 == 8

print(f" pow(3,2) = 3*3 -> {number2}")
assert number2 == 9

print(f" 2**3 = 2*2*2 -> {number3}")
assert number3 == 8

when we want the opposite of power we can either use math.sqrt() (square root) or fractions in math,pow()

import math

# when we user math.sqrt() method
number1 = math.sqrt(9)

# and we can use the math.power() with fractions
number2 = math.pow(9, 1/2)

# and we can use the math.power() with fractions
number3 = 9**(1/2)

# then we can see the power of the values
print(f" sqrt(9) -> {number1}")
assert number1 == 3

print(f" pow(9, 1/2) -> {number2}")
assert number2 == 3

print(f" 9**(1/2) -> {number3}")
assert number3 == 3

import math

# change the numbers to make the math work:
result1 = math.pow(1,1)
result2 = math.sqrt(4)
result3 = 1**2
result4 = 4**(1/2)
result5 = 9**(.5)

# then you must get the expected values
assert result1 == 25, f"{result1} != 25"
assert result2 == 4, f"{result1} != 4"
assert result3 == 16, f"{result1} -!= 16"
assert result4 == 6, f"{result1} != 6"
assert result5 == 8, f"{result1} != 8"

print("you did it!")

import math

# change the numbers to make the math work:
result1 = math.pow(5,2)
result2 = math.sqrt(16)
result3 = 2**4
result4 = 36**(1/2)
result5 = 64**(.5)

# then you must get the expected values
assert result1 == 25, f"{result1} != 25"
assert result2 == 4, f"{result1} != 4"
assert result3 == 16, f"{result1} -!= 16"
assert result4 == 6, f"{result1} != 6"
assert result5 == 8, f"{result1} != 8"

print("you did it!")

Logical operators: & , |

& and | is more about logic.

3 == 3 gives true, while 3==4 gives false

we can combine the the output with & and | operators.

Beware that in Python it is True and False, with UPPER CASE
In Groovy, JavaScript and C# it is true an false with lower case
In other languages it can be TRUE and FALSE.

The following gives an overview. It will make more sense with if-statements, that will come in a later lesson..

print("and &")
print(f"True & True   -> {True & True}")
print(f"True & False  -> {True & False}")
print(f"False & True  -> {False & True}")
print(f"False & False -> {False & False}")

print("----")
print("and |")
print(f"True | True   -> {True | True}")
print(f"True | False  -> {True | False}")
print(f"False | True  -> {False | True}")
print(f"False | False -> {False | False}")

True and false can also be written as 1 (true) and 0 (false)

print("and &")
print(f"1 & 1 -> {1 & 1}")
print(f"1 & 0 -> {1 & 0}")
print(f"0 & 1 -> {0 & 1}")
print(f"0 & 0 -> {0 & 0}")

print("----")
print("and |")
print(f"1 | 1 -> {1 | 1}")
print(f"1 | 0 -> {1 | 0}")
print(f"0 | 1 -> {0 | 1}")
print(f"0 | 0 -> {0 | 0}")

Data consistency operators: Math.abs()

Math.abs() makes all values positive.

import math
print(-5)
print(math.abs(-5))
print(math.abs(5))
print(5)

import math

# given you have the following values
number1 = -2
number2 = -3

# when you add them together correctly
result = number1 + number2

# then you must get the expected values
assert number1 == -2, f"number1 must be -2, but is {number1}"
assert number2 == -3, f"number1 must be -3, but is {number2}"
assert result == 5, f"result must be 5, but is {result}"

print("you did it!")

# when you add them together correctly
result = math.abs(number1) + math.abs(number2)

Other advanced operators

There are many other operators like: sin(), cos(), tan(), asin(), acos(), atan(), atan2(), log(), log10(), log2(), mean(), median(), variance(), std(), etc.

We will cover these in a later lesson.

Conclusion

Today, we embarked on an adventurous journey into the realm of operators, those magical symbols that enable us to manipulate data in programming.

We began by mastering arithmetic operators like addition, subtraction, multiplication, division, and modulus, empowering us to perform fundamental mathematical calculations effortlessly.

Transitioning to assignment operators, we learned to assign values to variables with “=“, and verify equality with “==“, streamlining our code for efficient data management.

We then ventured into comparison operators, including greater than (>), greater than or equal to (>=), lesser than (<), lesser than or equal to (<=), and not equal (!=), enabling us to make logical decisions based on variable comparisons.

To enhance code readability and efficiency, we embraced compound assignment operators like increment (+=), decrement (-=), multiply (*=), and divide (/=), simplifying variable modifications.

Delving deeper, we explored mathematical rounding techniques such as round(), math.floor(), and math.ceil(), ensuring precision in numerical calculations.

We harnessed the power of exponentiation with the ** operator and math.pow() function, facilitating easy calculation of powers and square roots math.sqrt().

Additionally, we harnessed logical operators like AND (&) and OR (|), enabling us to evaluate complex logical expressions with ease.

Ensuring data consistency operator, we utilized the Math.abs() function to transform negative numbers into positive ones, maintaining uniformity in data processing.

While we’ve only scratched the surface of operators in programming, today’s journey has provided us with a solid foundation to build upon. Armed with these newfound skills, we’re better equipped to tackle a wide array of computational tasks and navigate the diverse landscapes of programming with confidence.

Using AI

All this have been created with the cooperation with AI.

Often it can be more useful just to learn, what is needed in the moment, than to learn everything about a topic. This is where AI is perfect.

We can use the free ChatGPT 3.5 to learn about operators. You are welcome to try other and if you do, please write a comment!

Essential prompts can be:

When we don’t know the name of what we want to learn, then we can ask AI about it:

What do we call + - * and / in Python?

When we want to learn more about the topic

What other operators are there?

You can ask the same question twice and get more results:

Are there others?

Then you can explore each operator with:

I would like to learn more about Floor Division Operator //.

Can you make a assignment for me to solve?

The assignment needs to be written in Python as comments.
Use only given, when, and then comments. No code.

To get an assignment to learn from:

I would like to learn more about Floor Division Operator //.

Can you show me:
1. an example of how it works? (in python)
2. a real world application of it? (in python)

I want the code examples to be written with given, when, and then steps.
The then step needs to contain a print and assert (for manual and automatic verification)

And sometimes you might need to start a new session.

Sometimes the AI makes a mistake like writing Given, Then, When (wrong order) and sometimes starting a new session makes it go away.

And you can get AI to solve it for you:

Can you please solve this assignment for me in Python code?
--
# Given:
# Assume you are organizing a marathon event.
# You have a total of 152 registered participants.
# Each starting block can accommodate a maximum of 40 runners.

# When:
# Calculate the total number of starting blocks needed for the marathon.
# Use the floor division operator (//) to ensure that any partial block
# needed is rounded up to the nearest whole block.

# Then:
# Print the total number of starting blocks required for the marathon.
# Assert that the calculated total matches the expected value.
--

Congratulations – Lesson complete!

Musical Intro

Introduction

In programming, a “string” is simply text data – like words in a book or letters in your name.
Technically it is a variable, where you store text in it.

# when we have a text string
aTextString = "hello world"

# then we can print it to show it's content
print(aTextString)

Now you need to make a choice, how you want to learn it:

1. You can use AI to teach you. Then you can learn, by your own exploration and in any programming language (scroll down to Using AI)
2. You can use the result I got, from using AI. Then you can rely on my experience to filter it.(keep on reading)
3. You can also do both in any order :-)

Joining Strings Together (Adding / Concatenation)

# given we have two texts
var1 = "hello"
var2 = "world"

# when we add them together
result = var1 + var2 

# then they put together
print(result)
assert result == "helloworld"

Adding works differently with numbers:

# given we have two numbers
var1 = 1
var2 = 2

# when we add them together
result = var1 + var2 

# then they give the sum
print(result)
assert result == 3

If we put the numbers as text (with quotation marks), then they will add as strings and not numbers:

# given we have two numbers
var1 = "1"
var2 = "2"

# when we add them together
result = var1 + var2 

# then they put together (and not the sum)
print(result)
assert result == "12"

Also if you want to have a space between to words, that you add together, then you need to remember to also add a space:

# given we have two texts
text1 = "hello"
text2 = "world"
space = " " # the space

# when we add them together
result = text1+ space + text2

# then they put together
print(result)
assert result == "hello world"

Challenge, weather report

Try to write a code, where you

# given the weather is describe with the following parts:
city = "Praestoe"
temperature = "22°C"

# When we concatenate them to form a weather report
# (write your code here)

# Then the result should exactly match the expected report.
print(result)
assert result == "The current weather in Praestoe is 22°C"

result = "The current weather in " + city + " is " + temperature

G-, F-, Template- and interpolated-strings

G-Strings are a special kind of strings that are used in Groovy. They have other names in other languages:

They seem much more complex that a regular string, except they make our lives much easier.

Which one of these text addition do you find easiest to use?

# example 1 (the regular string)
result = "Mr. "+ name

# example 2 (the f-string)
result = f"Mr. {name}"

When we write a f in front of a “
Then we can just add { } with a variable name inside the text.

This makes it much easier with much more complicated strings, where we can use spaces inside the string, instead of adding extra spaces or adding them as variables:

# example 1 (the regular string)
result = title + " " + firstName + " " + lastName

# example 2 (the regular string with space variables)
result = title + space + firstName + space + lastName

# example 3 (the f-string)
result = f"{title} {firstName} {lastName}"

Challenge, F-weather

Rewrite the previous challenge by using f-strings

# given the weather is describe with the following parts:
city = "Praestoe"
temperature = "22°C"

# When we concatenate them to form a weather report
# (write your code here)

# Then the result should exactly match the expected report.
print(result)
assert result == "The current weather in Praestoe is 22°C"

Slicing

Since we can add strings together, then we can also slice them up into smaller parts and only keep the important part.

# given we have a text string
greeting = "Hello world"

# when we slice off the first letter
without_first = greeting[1:]

# then we only have the rest left
print(without_first)
assert without_first == "ello world"

And the same can be done on the other side of the string:

# given we have a text string
greeting = "Hello world"

# when we slice of the 2 last letters
without_last = greeting[:-2]

# then we only have the rest left
print(without_first)
assert without_first == "hello wor"

We use negative numbers, to count letters from the back of the string
We use positive numbers, to count letters from the front of the string

Challenge, slicing the world

# given we have a text string
greeting = "12345"

# when the ? is replaced with a positive number
result_1_1 = greeting[?:]
result_1_2 = greeting[:?]
result_1_3 = greeting[?:?]

# and the ? is replaced with a negative number
result_2_1 = greeting[:-?]
result_2_2 = greeting[-?:]
result_2_3 = greeting[-?:-?]

# then the strings are sliced to
assert result_1_1 == "2345"
assert result_1_2 == "12"
assert result_1_3 == "2"

assert result_2_1== "1234"
assert result_2_2== "45"
assert result_2_3== "4"

result_1_1 = greeting[?:] # [1:] from after letter 1
result_1_2 = greeting[:?] # [:2] until after letter 2
result_1_3 = greeting[?:?] # [1:2] from after letter 1 until after letter 2

result_2_1 = greeting[:?] # [:-1] until before letter 1 from behind
result_2_2 = greeting[?:] # [-2:] from before letter 2 from behind
result_2_3 = greeting[?:?] # [-2:-1] from before letter 2 from behind until

result_3_1 = greeting[?:?] # [1:-2]from after letter 1 until before letter -2 from behind
result_3_1 = greeting[?:?] # [-3:1]from after letter 1 until before letter -2 from behind

Length of a string

We can also measure the length of a string, which can be important if we want a password to have a minimum length.

Trim or strip

Sometimes Strings are written with spaces before and after the text: ” hello world “

The easiest way to remove the spaces is to use the command strip() in Python, trim() in JavaScript and Groovy, and Trim() in C#.

# Given the original text with leading and trailing space
originalText = " hello world "
print(f"original: ${originalText }")

# When we apply strip in it's 3 variations:
text1 = originalText.lstrip()
text2 = originalText.rstrip()
text3 = originalText.strip()

# Then text1 should be with no leading whitespace
print(f"lstrip:  |{text1}|")
assert text1 == "hello world "

# And text2 should be with no trailing whitespace
print(f"rstrip:  |{text2}|")
assert text2 == " hello world"

# And text3 should be with no leading or trailing whitespace
print(f"strip:   |{text3}|")
assert text3 == "hello world"

Padding

To add spaces, or any other symbol, before a text can be done with rjust() in Python, padStart() in JavaScript, padLeft() in Groovy, PadLeft() in C#.

To add spaces, or any other symbol, after a text can be done with ljust() in Python, padEn() in JavaScript, padRight() in Groovy, PadRight() in C#.

# Given product names and prices
product1 = "Orange"
price1 = "25 EUR"

product2 = "Computer"
price2 = "1000 EUR"


# When combining product names and prices with normal addition
productText1a = product1 + " " + price1
productText2a = product2 + " " + price2

# Then the product text is not formatting in a pretty way
print(productText1a)
print(productText2a)
print("---------  ---------")


# When aligning product names with spaces as padding
productText1b = product1.ljust(10, " ") + price1.rjust(10, " ")
productText2b = product2.ljust(10, " ") + price2.rjust(10, " ")

# Then the product text should have a pretty formatting
print(productText1b)
print(productText2b)
print("---------  ---------")


# When aligning product names with dots as padding
productText1c = product1.ljust(10, ".") + price1.rjust(10, ".")
productText2c = product2.ljust(10, ".") + price2.rjust(10, ".")

# Then the product text should have even prettier formatting
print(productText1c)
print(productText2c)
print("---------  ---------")

Which will give the following output:

Escape sequences to make line breaks, tabulators, and quotes within quotes

To have a line break in a string, then a \n can be put into it. Because we can’t write:

print("line 1
line 2")
# creates an error

To have a tab a \t can be use, even though we sometimes can add tabs, but not always. Sometimes they are added as 2 or 4 spaces instead of a tab:

print("word 1  word 2")
# creates an error

To have a quote within a quote requires an \”, because we can’t write the following without creating an error:

print("word 1 "word 2" word 3")
# creates an error

And because we use \ to write special characters, we need to write \\ to tell the computer we want to write an \, otherwise it will expect an special character.

To write it correctly please do:

Conclusion

Today, we took a fun dive into the colorful world of strings, discovering that strings are like little containers for text—holding everything from single words to lengthy paragraphs.

We kicked things off by learning how to add strings together, transforming “hello” and “world” into “hello world.”

We then looked into f-strings (Python), G-strings (Groovy), template-strings (JavaScript) and interpolated strings (C#).

We also got crafty with slicing strings, which is a bit like sculpting: you chisel away the parts you don’t need or shuffle them around to create something entirely new.

And we played around with replacing a word in a string with another word. Quite fancy when you want to anonymize a text.

We also looked into the length of strings. It’s like having a tiny ruler at your fingertips, perfect for checking the length of a text, ensuring passwords meet security standards, or just satisfying your curiosity about how much you’ve actually typed.

We played with to uppercase and lowercase, which helps keep everything looking neat and tidy, no matter how chaotic the input might be.

We ended with a fun exercise where we had to combine all what we learned together, by making “eLISAbeTH “into “Elisabeth”

We looked into trim/strip to remove spaces.

Padding to add spaces and other symbols.

Escape sequences such as line breaks, tabulators, and quotes within quotes.

By now, you should feel pretty equipped to handle text in your programming projects. Whether you’re crafting messages, tidying up data, or just indulging your inner nerd, the skills you’ve embraced today are essential tools in your programming kit. Let’s keep that inner child curious and eager to learn more as we continue exploring the vast and vibrant world of coding!

---

Using AI

All this have been created with the cooperation with AI.

Often it can be more useful just to learn, what is needed in the moment, than to learn everything about a topic. This is where AI is perfect.

We can use the free ChatGPT 3.5 to learn about operators. You are welcome to try other and if you do, please write a comment!

Essential prompts can be:

Learning about Strings

I would like to learn about Strings (text) in Python.
What things are critical to learn?

When we want to learn more about the topic

I would like to learn more about Escape Sequences, what should I be able to do?

It answered much more, but there is no need to show it all, because the amount of data can be overwhelming: (Multiline Strings, Unicode Character, Escape Sequence as Literal, Control Characters, Hexadecimal and Octal Escapes)

Take one of them and go further into it.

Then you can explore each theme with:

I would like to learn more about Special Characters such as '\n', '\t', and '\\'.

Can you show me:
1. an example of how it works? (in python)
2. a real world application of it? (in python)

I want the code examples to be written with given, when, and then steps.
The then step needs to contain a print and assert (for manual and automatic verification)

And we can always test the code in our web editors: 💻 Python / 💻 JavaScript / 💻 Groovy / 💻 C#

To get an assignment to learn from:

Can you make a assignment for me to solve?
It has to be about using Special Characters such as '\n', '\t', and '\\'.

The assignment needs to be written in Python as comments.
Use only given, when, and then comments. No code.

And sometimes you might need to start a new session.

Sometimes the AI makes a mistake like writing Given, Then, When (wrong order) and sometimes starting a new session makes it go away.

And you can get AI to solve it for you:

Can you please solve this assignment for me in Python code?
--
# Given a string containing multiple lines of text separated by '\n' characters,
# where some words are separated by '\t' characters,
# and some backslashes are used to escape special characters.

# When the string is given as input,
# Then write a Python program to perform the following tasks:

# 1. Split the string into individual lines using the '\n' character as the delimiter.
# 2. For each line, split the line into words using the '\t' character as the delimiter.
# 3. If a word contains the sequence '\\', replace it with a single backslash character '\'.
# 4. Print each word on a new line.

# For example:
# Given input string:
# "Hello\tworld!\nThis\tis\tan\texample\nString\twith\\tSpecial\tCharacters\n"

# The output should be:
# Hello
# world!
# This
# is
# an
# example
# String
# with\tSpecial
# Characters
--

And we can run it in our web editor:

You can ask for a new assignment – as many times as you want.

You can make the AI solve it for you.
You can make the AI help you solve it.
You can solve it yourself.
Limitless learning with a 24/7 tutor!!!

Congratulations – Lesson complete!

Musical Intro

Why variables?

Ever wonder how your favorite video games come to life?

Picture invisible shelves filled with jars, each holding pieces of the game world.

One jar might decide the name of your character, , while another controls the speed of your racing car.

const charachterName = "Bartek";
let maxSpeedOfCar =  200;

In the example above we set the characterName to be “Bartek” and the maxSpeedOfCar to 200.

These jars or variables are at work behind the scenes, making digital experiences thrilling and interactive. They’re the unseen magic that breathes life into pixels and bytes, transforming them into adventures and stories that enthrall us.

Naming variables

The name of a variable has 2 important parts:

1. Computer friendly name: The computer needs to be able to read the name.
2. Human friendly name: We coders need to know, what the variable contains

Computer friendly name

For the computer to read it, it needs to be a single text without spaces:

There is also PascalCase, snake_case, UPPER_SNAKE_CASE, kebab-case, etc. but we will cover them, when the need arise.

Human friendly name

It is also a good idea to give it a name, that we humans can understand, because it will be difficult to understand what this code do:

fn = t + n1 + n2

While this is much easier to read:

fullName = title + firstName + lastName

because we can read, that we take the title putting it together with the first name and the last name and store it as the full name.

Questions about naming

Which variables are ok, and which are not?

const playerName = "Bartek"
const player name = "Bartek"
const player-name = "Bartek"
const pn = "Bartek"
const PlayerName = "Bartek"

Assigning a variable

We assign variables in different ways in different languages.
Just select the language, that you would like to learn. No need to learn all of them.
We use constants, when we don’t want the value to change in the future.
We use variable, when we want the value to change in the future.

GREETING = "hello" 
name = "Bartek"
name = "Patrick"
GREETING = "hi"

const GREETING = "hello";
let name = "Bartek";

name = "Patrick";
GREETING = "hi"; // this will throw an error

def GREETING = "hello" 
def name = "Bartek"
name = "Patrick"
GREETING = "hi"

const string GREETING = "hello";
int name = 2;

name = 3;
GREETING = "hi" // this will throw an error
name = "Bartek" // will also throw an error

Challenges introduction

You can use free ChatGPT 3.5 to translate it from Python to other languages (read how)

And use the Web editors: 💻 Python / 💻 JavaScript / 💻 Groovy / 💻 C#

We have this working code example for inspiration, to solve the challenges:

# Given we have 2 numbers: 1 and 2
number1 = 1
number2 = 2

# When we add them together
result = number1 + number2

# Then the result will be printed and asserted
print(result)
assert result == 3

Challenge 1

Can you add the required details, to make the code work?

# Given we have 3 numbers: 1, 2, 3
number1 = 1
number2 = 2
# <add something here>

# When we add them together
result = number1 + number2

# Then the result will be printed and asserted
print(result)
assert result == 6

Challenge 2

Can you add the required details, to make the code work?

# Given we have 4 numbers: 1, 2, 3, 5

# When we add them together

# Then the result will be printed and asserted
print(result)
assert result == 11

Challenge 3

Can you add the required details, to make the code work?

# Given we have 5 numbers: 1, 2, 3, 5, 7

# When we add them together

# Then the result will be printed and asserted

Conclusion

In the journey through the realms of coding, we’ve seen how variables act as the fundamental building blocks, allowing us to store, manipulate, and retrieve data with ease.

Just as jars can hold anything from spices to cookies in the kitchen, variables in programming hold the pieces that bring digital experiences to life, from the names of characters in a video game to the speeds of racing cars.

We learned to name variables, so we know what they actually mean, because anyone can understand ourAge = yourAge + myAge, while nobody can guess what oa = ya + ma means.

We learned to use camelCase for variables, and CAPITAL for constants. And remember not to use spaces, because computers don’t get understand it.

You have also solved 3 challenges – congratulations!

Remember, the power of coding is at your fingertips, and variables are one of the first keys to unlocking that potential. Happy coding!

And you can always create your own challenges, with multiple variables, different values or even using minus, multiplication, or division, instead of plus.

Congratulations – Lesson complete!

How to write a comment:

# This is a comment in Python

// This is a comment in Python

// This is a comment in Python

// This is a comment in Python

Congratulations – Lesson complete!