What is the Random Module?
The random module in Python is used to generate pseudo-random numbers. It’s perfect for:
- Games
- Simulations
- Random sampling
- Shuffling data
- Generating test data
Random Module Methods with Examples
1. random() – Random float between 0.0 and 1.0
Generates a random floating-point number between 0.0 (inclusive) and 1.0 (exclusive).
python
import random
# Example 1: Basic random float
print(random.random()) # Output: 0.5488135079477204
# Example 2: Simulating probability (50% chance)
if random.random() < 0.5:
print("Heads!")
else:
print("Tails!")
# Example 3: Generating percentage-like values
percentage = random.random() * 100
print(f"Progress: {percentage:.2f}%") # Output: Progress: 73.42%
2. uniform(1, 10) – Random float in specified range
Returns a random float between the specified range (inclusive of endpoints).
python
import random
# Example 1: Basic float in range
print(random.uniform(1, 10)) # Output: 6.423434
# Example 2: Temperature simulation
temperature = random.uniform(20.0, 35.5)
print(f"Current temperature: {temperature:.1f}°C") # Output: Current temperature: 28.7°C
# Example 3: Price range
price = random.uniform(99.99, 199.99)
print(f"Product price: ${price:.2f}") # Output: Product price: $156.75
3. randint(1, 100) – Random integer in range
Returns a random integer between the specified range (inclusive of both endpoints).
python
import random
# Example 1: Basic random integer
print(random.randint(1, 100)) # Output: 57
# Example 2: Dice roller (six-sided die)
dice_roll = random.randint(1, 6)
print(f"Dice roll: {dice_roll}") # Output: Dice roll: 4
# Example 3: Age generator
age = random.randint(18, 65)
print(f"Random age: {age} years") # Output: Random age: 34 years
4. randrange(1, 10, 2) – Random with step control
Returns a randomly selected element from a range with specified step.
python
import random
# Example 1: Odd numbers between 1-10
print(random.randrange(1, 10, 2)) # Output: 7 (from 1,3,5,7,9)
# Example 2: Even numbers between 0-20
even_num = random.randrange(0, 21, 2)
print(f"Even number: {even_num}") # Output: Even number: 14
# Example 3: Multiples of 5 between 5-50
multiple_of_5 = random.randrange(5, 51, 5)
print(f"Multiple of 5: {multiple_of_5}") # Output: Multiple of 5: 35
5. choice(list) – Random element from sequence
Returns a random element from a non-empty sequence.
python
import random
# Example 1: Random name from list
names = ["Alice", "Bob", "Charlie", "Diana"]
print(random.choice(names)) # Output: Charlie
# Example 2: Random weekday
weekdays = ["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"]
print(f"Random day: {random.choice(weekdays)}") # Output: Random day: Wed
# Example 3: Rock, Paper, Scissors
choices = ["Rock", "Paper", "Scissors"]
computer_choice = random.choice(choices)
print(f"Computer chose: {computer_choice}") # Output: Computer chose: Paper
6. choices(list, k=2) – Multiple random elements
Returns multiple random elements from a sequence (with replacement).
python
import random
# Example 1: Multiple names
names = ["Alice", "Bob", "Charlie", "Diana"]
print(random.choices(names, k=2)) # Output: ['Bob', 'Alice']
# Example 2: Lottery numbers (can have duplicates)
lottery = random.choices(range(1, 51), k=6)
print(f"Lottery numbers: {lottery}") # Output: Lottery numbers: [12, 45, 12, 33, 7, 28]
# Example 3: Random team selection
players = ["Player1", "Player2", "Player3", "Player4"]
team = random.choices(players, k=2)
print(f"Team members: {team}") # Output: Team members: ['Player3', 'Player1']
7. shuffle(list) – Shuffle sequence in-place
Randomizes the order of elements in a list (modifies the original list).
python
import random
# Example 1: Shuffle a list of numbers
numbers = [1, 2, 3, 4, 5]
random.shuffle(numbers)
print(numbers) # Output: [3, 1, 5, 2, 4]
# Example 2: Shuffle a deck of cards
cards = ["Ace", "King", "Queen", "Jack", "10"]
random.shuffle(cards)
print(f"Shuffled deck: {cards}") # Output: Shuffled deck: ['Jack', 'Ace', '10', 'Queen', 'King']
# Example 3: Shuffle quiz questions
questions = ["Q1", "Q2", "Q3", "Q4", "Q5"]
random.shuffle(questions)
print(f"Quiz order: {questions}") # Output: Quiz order: ['Q4', 'Q1', 'Q3', 'Q5', 'Q2']
8. seed(10) – Initialize random generator
Sets the seed value for reproducible random sequences.
python
import random
# Example 1: Reproducible random numbers
random.seed(10)
print(random.random()) # Always: 0.5714025946899135
print(random.random()) # Always: 0.4288890546751146
# Example 2: Same seed = same results
random.seed(42)
result1 = [random.randint(1, 10) for _ in range(3)]
random.seed(42)
result2 = [random.randint(1, 10) for _ in range(3)]
print(f"Result 1: {result1}") # Output: Result 1: [2, 1, 5]
print(f"Result 2: {result2}") # Output: Result 2: [2, 1, 5] (same!)
# Example 3: Testing with fixed seed
random.seed(123)
test_data = [random.uniform(0, 1) for _ in range(3)]
print(f"Test data: {test_data}") # Always same for testing
9. getstate() / setstate() – Save/restore random state
Saves and restores the internal state of the random number generator.
python
import random
# Example 1: Save and restore state
print("First number:", random.randint(1, 100)) # Output: First number: 45
# Save current state
state = random.getstate()
print("Second number:", random.randint(1, 100)) # Output: Second number: 78
print("Third number:", random.randint(1, 100)) # Output: Third number: 23
# Restore to saved state
random.setstate(state)
print("After restore:", random.randint(1, 100)) # Output: After restore: 78 (same as second)
print("Next number:", random.randint(1, 100)) # Output: Next number: 23 (same as third)
# Example 2: Continue from saved point
random.seed(100)
print(random.random()) # Output: 0.1456692551041303
saved_state = random.getstate()
print(random.random()) # Output: 0.45492700451402135
random.setstate(saved_state)
print(random.random()) # Output: 0.45492700451402135 (same as above)
# Example 3: Multiple save points
state1 = random.getstate()
num1 = random.randint(1, 10)
state2 = random.getstate()
num2 = random.randint(1, 10)
random.setstate(state1)
print(f"From state1: {random.randint(1, 10)}") # Same as num1
random.setstate(state2)
print(f"From state2: {random.randint(1, 10)}") # Same as num2
10. getrandbits(3) – Random number by bit count
Generates a random number with the specified number of bits.
python
import random
# Example 1: 3 bits (0-7 range)
print(random.getrandbits(3)) # Output: 5 (binary: 101)
# Example 2: Different bit sizes
print(f"4 bits: {random.getrandbits(4)}") # Range: 0-15
print(f"8 bits: {random.getrandbits(8)}") # Range: 0-255
print(f"16 bits: {random.getrandbits(16)}") # Range: 0-65535
# Example 3: Generating binary numbers
bits_3 = random.getrandbits(3)
bits_5 = random.getrandbits(5)
print(f"3-bit number: {bits_3} (binary: {bin(bits_3)})")
print(f"5-bit number: {bits_5} (binary: {bin(bits_5)})")
# Output: 3-bit number: 3 (binary: 0b11)
# Output: 5-bit number: 17 (binary: 0b10001)
📊 Quick Reference
| Method | Purpose | Range/Output |
|---|---|---|
random() | Random float | 0.0 to 1.0 |
uniform(a,b) | Float in range | a to b |
randint(a,b) | Integer in range | a to b (inclusive) |
randrange(s,e,step) | Integer with step | s to e with step |
choice(seq) | One random element | From sequence |
choices(seq,k) | Multiple elements | List of k elements |
shuffle(list) | Reorder list | Modifies original |
seed(n) | Set starting point | Reproducible results |
getstate()/setstate() | Save/restore | Continue sequence |
getrandbits(k) | Random by bits | 0 to 2^k-1 |
