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