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Anubhav Kumar

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The Anubhav portal was launched in March 2015 at the behest of the Hon'ble Prime Minister for retiring government officials to leave a record of their experiences while in Govt service .

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Anubhav Kumar

Anubhav Kumar

25-Nov-2025

NumPy Random Numbers

NumPy provides random number functions through:

numpy.random

There are many ways to generate random numbers:

1. Random Integer (randint)

import numpy as np

# Random integer between 0 and 10 (exclusive)
x = np.random.randint(0, 10)
print(x)

Generate multiple random integers:

arr = np.random.randint(0, 100, size=5)
print(arr)

2. Random Floats (rand, randn, random)

Uniform distribution (0 → 1)

x = np.random.rand()
print(x)

Multi-dimensional:

arr = np.random.rand(3, 2)
print(arr)

Normal distribution (mean=0, std=1)

x = np.random.randn(5)
print(x)

General random floats

arr = np.random.random((2, 3))
print(arr)

3. Random Choice (choice)

Select random values from a list or array:

items = np.array([10, 20, 30, 40, 50])

x = np.random.choice(items)
print(x)

Select multiple:

arr = np.random.choice(items, size=3)
print(arr)

With replacement disabled:

np.random.choice(items, size=3, replace=False)

4. Random Shuffle

Shuffle array in-place:

arr = np.array([1, 2, 3, 4, 5])
np.random.shuffle(arr)

print(arr)

5. Random Permutation (returns new array)

arr = np.random.permutation(10)
print(arr)

6. Random Seed (reproduce results)

To get same random numbers every time:

np.random.seed(42)

print(np.random.rand(3))

If you run again with seed=42, output will match exactly.

7. Random distribution samples

Normal distribution with custom mean & std

arr = np.random.normal(loc=50, scale=10, size=5)
print(arr)

Binomial distribution

arr = np.random.binomial(n=10, p=0.5, size=5)
print(arr)

Poisson distribution

arr = np.random.poisson(lam=4, size=5)
print(arr)

8. New Generator API (recommended)

NumPy recommends using:

rng = np.random.default_rng()

Example:

rng = np.random.default_rng()

print(rng.integers(0, 10, size=5))
print(rng.random(3))

Summary Table

Purpose Function
Random integer randint, integers
Random float 0–1 rand, random
Normal distribution randn, normal
Random choice from array choice
Shuffle array shuffle, permutation
Reproducibility seed
Modern API default_rng()

 

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