Skip to content

Data types and Variables

Variables

Variables are used to store data in a program. They are like containers that hold values. You can think of them as labels that you can assign to values. In Python, you can create a variable by giving it a name and assigning a value to it using the = operator.

# Assigning a value to a variable
x = 10
y = 3.14
name = "Alice"
is_student = True

Data Types

Numbers

  • Integers (int): represent whole numbers (positive, negative, or zero) with unlimited size. Examples: 10, -23, 0.

  • Floats (float): represent decimal numbers with limited precision (approximately 15 decimal places). Examples: 3.14, -5.2e10 (scientific notation).

Strings

  • A string is a sequence of characters enclosed within single or double quotes. Examples: "hello", 'world', "123".

Boolean

  • A boolean value is either True or False. It is used to represent truth values. Examples: True, False.

None

  • The None keyword is used to represent the absence of a value. It is similar to null in other programming languages.

Operators

Arithmetic Operators

  • + (addition)
  • - (subtraction)
  • * (multiplication)
  • / (division)
  • % (modulus)
  • ** (exponentiation)
  • // (floor division)
# Arithmetic operators
x = 10
y = 3
print(x + y)  # 13
print(x - y)  # 7
print(x * y)  # 30
print(x / y)  # 3.3333333333333335
print(x % y)  # 1
print(x ** y) # 1000
print(x // y) # 3

Comparison Operators

  • == (equal to)
  • != (not equal to)
  • < (less than)
  • > (greater than)
  • <= (less than or equal to)
  • >= (greater than or equal to)
# Comparison operators
x = 10
y = 5
print(x == y)  # False
print(x != y)  # True
print(x < y)   # False
print(x > y)   # True
print(x <= y)  # False
print(x >= y)  # True

Logical Operators

  • and (logical and)
  • or (logical or)
  • not (logical not)
# Logical operators
x = True
y = False
print(x and y)  # False
print(x or y)   # True
print(not x)    # False

Assignment Operators

  • = (assign value)
  • += (add and assign)
  • -= (subtract and assign)
  • *= (multiply and assign)
  • /= (divide and assign)
  • %= (modulus and assign)
  • **= (exponentiate and assign)
  • //= (floor divide and assign)
# Assignment operators
x = 10
x += 5  # equivalent to x = x + 5
x -= 3  # equivalent to x = x - 3
x *= 2  # equivalent to x = x * 2
x /= 4  # equivalent to x = x / 4
x %= 3  # equivalent to x = x % 3
x **= 2 # equivalent to x = x ** 2
x //= 5 # equivalent to x = x // 5

Identity Operators

  • is (object identity)
  • is not (negated object identity)
# Identity operators
x = [1, 2, 3]
y = [1, 2, 3]
z = x
print(x is y)    # False
print(x is not y) # True
print(x is z)    # True

Membership Operators

  • in (sequence membership)
  • not in (negated sequence membership)
# Membership operators
x = [1, 2, 3, 4, 5]
print(3 in x)    # True
print(6 not in x) # True

Type Conversion

You can convert between different data types using built-in functions like int(), float(), str(), bool(), etc.

# Type conversion
x = 10
y = 3.14
z = "20"
print(float(x))  # 10.0
print(int(y))    # 3
print(int(z))    # 20
print(str(x))    # '10'
print(bool(x))   # True
print(bool(0))   # False

Input and Output

Input

You can use the input() function to take user input from the keyboard. The input is always returned as a string.

# Input
name = input("Enter your name: ")
print("Hello, " + name)

Output

You can use the print() function to display output on the screen. You can pass multiple arguments to print() separated by commas.

# Output
x = 10
y = 3.14
name = "Alice"
print("The value of x is", x)
print("The value of y is", y)
print("Hello,", name)

Comments

Comments are used to explain the code and make it more readable. In Python, you can use the # symbol to write a single-line comment.

# This is a single-line comment

For multi-line comments, you can enclose the text within triple quotes.

"""
This is a
multi-line comment
"""