Introduction to Operations

What are operations?

Operations are actions you can perform on values and variables in your program. You can think of them as the “verbs” of programming - they tell the computer what to do with data (values and variables).

Example:

# Feel free to play around with this code age = 25 next_year = age + 1 print(next_year) 





Here, + is an operation that adds two numbers together.



Operators



An operator is a symbol that performs an operation. It’s like a mathematical symbol that tells the computer what action to take.



Examples of operators:


    
  
  • + (addition operator)
    • 
  
  • - (subtraction operator)
    • 
  
  • == (equality operator)
    • 
  
  • * (multiplication operator)
    • 







Arithmetic Operations



These operations work with numbers (integers and floats):



1. Addition (+)



The + symbol adds two numbers together.




  

# Feel free to play around with this code
score1 = 85
score2 = 92
total = score1 + score2
print(total)  


  
  






  

# Feel free to play around with this code
score1 = 85.5
score2 = 92.3
total = score1 + score2
print(total)  


  
  





2. Subtraction (-)



The - symbol subtracts one number from another.




  

# Feel free to play around with this code
price = 50
discount = 10
final_price = price - discount
print(final_price) 


  
  





3. Multiplication (*)



The * symbol multiplies two numbers.




  

# Feel free to play around with this code
length = 5
width = 3
area = length * width
print(area)  


  
  





4. Division (/)



The / symbol divides one number by another (always gives a float result).




  

# Feel free to play around with this code
total_cookies = 20
people = 4
cookies_per_person = total_cookies / people
print(cookies_per_person)  


  
  





5. Integer Division (//)



The // symbol divides and rounds down to the nearest whole number.




  

# Feel free to play around with this code
total_cookies = 23
people = 4
whole_cookies = total_cookies // people
print(whole_cookies) 


  
  





6. Modulo (%)



The % symbol gives the remainder after division.




  

# Feel free to play around with this code
total_cookies = 23
people = 4
leftover_cookies = total_cookies % people
print(leftover_cookies)  


  
  





7. Exponentiation (**)



** raises a number to a power.




  

# Feel free to play around with this code
base = 2
power = 3
result = base ** power
print(result)  


  
  





Order of Operations



Python follows mathematical order of operations (PEMDAS):


    
  
  1. Parentheses ()
    2. 
  
  2. Exponents **
    3. 
  
  3. Multiplication * and Division /
    4. 
  
  4. Addition + and Subtraction -
    5. 





  

# Feel free to play around with this code
result = 2 + 3 * 4
print(result)  

result_with_parentheses = (2 + 3) * 4
print(result_with_parentheses)  
```


  
  








Comparison Operations



These operations compare values and give True or False results:



1. Equal to (==)



The double equals == symbol checks if two values are the same (this is different from a single =, which assigns a value to a variable).




  

# Feel free to play around with this code
age = 18
is_adult = age == 18
print(is_adult)  


  
  





2. Not equal to (!=)



The symbol ! when combined with = negates equality, therefore != checks if two values are different.




  

# Feel free to play around with this code
password = "secret"
is_wrong = password != "password123"
print(is_wrong)  


  
  





3. Greater than (>)



The symbol > checks if the value on the left is greater than the value on the right.




  

# Feel free to play around with this code
score = 85
passed = score > 60
print(passed) 


  
  





4. Less than (<)



The symbol < checks if the value on the left is less than the value on the right.




  

temperature = 15
is_cold = temperature < 20
print(is_cold)  # Output: True


  
  





5. Greater than or equal to (>=)



Combining the > symbol and = in >= checks if the value on the left is greater than or equal to the value on the right.




  

# Feel free to play around with this code
age = 18
can_vote = age >= 18
print(can_vote)  


  
  





6. Less than or equal to (<=)


Combining the < symbol and = in <= checks if the value on the left is less than or equal to the value on the right.




  

# Feel free to play around with this code
speed = 50
within_limit = speed <= 60
print(within_limit) 


  
  








String Operations



1. Concatenation (+)


When applied to strings, the + symbol joins strings together.




  

# Feel free to play around with this code
first_name = "Alice"
last_name = "Smith"
full_name = first_name + " " + last_name
print(full_name)  


  
  





2. Repetition (*)


When applied to strings, the * symbol repeats a string multiple times.




  

# Feel free to play around with this code
laugh = "ha"
big_laugh = laugh * 3
print(big_laugh) 


  
  








Practice Exercises



Test your understanding of operations with these exercises.



Q1: Multiplication and addition



Write a program that asks the user for the length and width of a rectangle, then calculates and displays both the area and perimeter.



Formulas:


    
  
  • Area = length × width
    • 
  
  • Perimeter = 2 × (length + width)
    • 




Expected output:


Enter length: 5
Enter width: 3
Area: 15.0
Perimeter: 16.0





  Example solution
  
area = length * width
perimeter = 2 * (length + width)

print(f"Area: {area}")
print(f"Perimeter: {perimeter}")

  





Q2: Integer division and modulo



Write a program that asks how many cookies you have and how many people need to share them. Calculate:


    
  
  • How many whole cookies each person gets
    • 
  
  • How many cookies are left over
    • 




Expected output:


How many cookies do you have? 23
How many people are sharing? 5
Each person gets: 4 cookies
Leftover cookies: 3





  Example solution
  
cookies_per_person = total_cookies // people
leftover = total_cookies % people

print(f"Each person gets: {cookies_per_person} cookies")
print(f"Leftover cookies: {leftover}")

  





Q3: Comparison operators



Write a program that asks for a temperature in Celsius and checks if it’s:


    
  
  • Below freezing (< 0)
    • 
  
  • At freezing (== 0)
    • 
  
  • Above freezing but cool (> 0 and <= 15)
    • 
  
  • Warm (> 15)
    • 




Display an appropriate message for each case.



Expected output:


Enter temperature in Celsius: -5
It's below freezing!

Enter temperature in Celsius: 0
It's exactly freezing point.

Enter temperature in Celsius: 10
It's above freezing but cool.

Enter temperature in Celsius: 20
It's warm!





  Example solution
  
if temp < 0:
    print("It's below freezing!")
elif temp == 0:
    print("It's exactly freezing point.")
elif temp <= 15:
    print("It's above freezing but cool.")
else:
    print("It's warm!")

  





Q4: String concatenation and repetition



Write a program that asks the user for:


    
  
  • Their name
    • 
  
  • A word they want to repeat
    • 
  
  • How many times to repeat it
    • 




Then display:


    
  
  • A personalized greeting using their name
    • 
  
  • The word repeated the specified number of times
    • 




Expected output:


Enter your name: Alice
Enter a word to repeat: Hello
How many times? 3
Hi Alice, nice to meet you!
HelloHelloHello





  Example solution
  
greeting = "Hi " + name + ", nice to meet you!"
repeated_word = word * times

print(greeting)
print(repeated_word)

  


  
Alternative using f-strings:

  
name = input("Enter your name: ")
word = input("Enter a word to repeat: ")
times = int(input("How many times? "))

print(f"Hi {name}, nice to meet you!")
print(word * times)