Variable Examples in Python

Variable Naming Rules

• Variable names should start with alphanumeric characters, an underscore (_), or a string.
• Variable names must not start with numbers or hyphens.
• Variable names are case-sensitive.

Invalid Variable Examples

# Throws `SyntaxError: invalid decimal literal`
# 1fruit = 'hello'

# Throws `SyntaxError: cannot assign to expression here. Maybe you meant '==' instead of '='?`
# -adhi = 'graduated'
# =adhi = 'graduated'

Multiple Variables

Assigning Multiple Values

x, y, z = 1, 2, "Three"
print(f"X is {x}, Y is {y}, Z is {z}")

Swapping Variables

Using Unpacking

a = 'apple'
b = 'bat'
b, a = a, b  # Time and Space complexity is O(1)
print(f"After Unpacking: A value is {a}, B value is {b}")

- Time Complexity: O(1) - Simply swapping references to the string objects. - Space Complexity: O(1) - No additional space is required.

Using Additional Memory

c = b
b = a
a = c
print(f"After using additional memory: A value is {a}, B value is {b}")

- Time Complexity: O(1) - Each assignment is a constant-time operation. - Space Complexity: O(1) - Introduces a single additional variable c.

Using Slicing Without Additional Memory

a = a + b
b = a[:len(a) - len(b)]
a = a[len(b):]
print(f"After Slicing: A value is {a}, B value is {b}")

- Time Complexity: O(n + m) - Where n is the length of string a and m is the length of string b. - Space Complexity: O(n + m) - Slicing operations create new strings.

Integer Swapping

Using Unpacking

a = 1
b = 2
b, a = a, b
print(f"Now Integer A position is {a}, B position is {b}")

Using Arithmetic Operations

a = a + b
b = a - b
a = a - b
print(f"After computation of a+b, a-b, a-b ==== Now Integer A position is {a}, B position is {b}")

Using XOR Approach

a ^= b
b ^= a
a ^= b
print(f"After XOR Approach ==== Now Integer A position is {a}, B position is {b}")

One Value to Multiple Variables

previous = current = next = 1
print(f"previous: {previous}, current: {current}, next: {next}")

Unpack a Collection

List Example

fruits = ["apple", "banana", "cherry"]
firstFruit, secondFruit, thirdFruit = fruits
print(f"firstFruit: {firstFruit}, secondFruit: {secondFruit}, thirdFruit: {thirdFruit}")