Operators and String Manipulation

Operators — The Tools of Calculation

An operator tells Python how to combine or compare values. There are three categories you must know: arithmetic, relational, and logical. Understanding them precisely matters because exam questions often test the output of specific expressions — especially for relational operators where the expected output is True or False, not “yes” or “no”.

Arithmetic Operators

Python supports seven arithmetic operators. Four are familiar: + (addition), - (subtraction), * (multiplication), / (real division — the result can be a decimal). The other three are integer division (//), modulus (%) and exponentiation (**).

print(17 // 5)    # Integer division: 3 (5 goes into 17 three full times)
print(17 % 5)     # Modulus: 2 (17 = 3*5 + 2, remainder is 2)
print(2 ** 8)     # Exponentiation: 256 (2 to the power of 8)
print(7 / 2)      # Real division: 3.5

Relational Operators

Relational operators compare two values and always return a Boolean: True or False. This is a common exam error — students write “yes” or “1” when the correct answer is True.

print(10 == 10)   # True
print(10 != 5)    # True
print(3 < 2)      # False
print(5 >= 5)     # True

The six relational operators are: == (equal to), != (not equal to), < (less than), > (greater than), <= (less than or equal to), >= (greater than or equal to). Note that == tests equality; a single = in Python is assignment, not comparison.

Logical Operators

Logical operators combine or invert Boolean conditions. Python uses and, or, and not (all lowercase).

age = 17
has_consent = True

if age >= 16 and has_consent:
    print("Eligible for trip")

if age < 13 or age > 65:
    print("Reduced price ticket")

if not has_consent:
    print("Permission required")

String Operations

Python has powerful built-in tools for working with strings. The length of a string is found with len(). Indexing retrieves a single character by position, starting at 0. Slicing extracts a section of the string.

name = "Computer"
print(len(name))       # 8
print(name[0])         # C (first character, index 0)
print(name[3])         # p (index 3)
print(name[0:4])       # Comp (index 0 up to but not including 4)

Case Conversion and Concatenation

Python provides two methods for changing a string’s case: .upper() returns a version with all letters capitalised; .lower() returns a version with all letters in lowercase. These are useful when comparing user input regardless of how it was typed.

city = "London"
print(city.upper())    # LONDON
print(city.lower())    # london

# Safe comparison:
response = input("Enter yes or no: ")
if response.lower() == "yes":
    print("Confirmed")

Concatenation joins strings together using +. Only strings can be concatenated — trying to add a string and an integer gives a TypeError. Use str() to convert a number to a string first: "Score: " + str(85).

first_name = input("First name: ")
surname = input("Surname: ")
username = first_name[0].lower() + surname.lower()
print("Username:", username)