Python random Introduction














































Python random Introduction



INTRODUCTION TO PYTHON random MODULE

 Python has a built-in random module that implements pseudo-random number generators for various distributions.This module contains methods that let us directly solve many different programming issues where randomness comes into play.
The random module is based on Marsenne Twister - a very popular algorithm, which is the default pseudo-random number generator not only for Python, but also for many other popular software systems such as Microsoft Excel, MATLAB, R, or PHP. Its important advantages include permissive licensing, random-likeness confirmed by many statistical tests, and relatively high speed compared to other pseudo random number generators.

What are Pseudo Random Number Generators ?

 In many programming cases, all we need are sets of numbers that seem random. This kind of data can be derived from pseudo-random number generators. These are algorithms, that use a tiny portion of information (called a seed) and then apply complicated mathematical formulas in order to generate deterministic sets of numbers resembling truly random sets.
How to use a random module?
 You need to import the random module in your program, and you are ready to use this module. Use the following statement to import the random module in your code.

import random

Code for some random module functions use:

Output:


random Module Functions :-

  • random() is the most basic function of the random module.
  • Almost all functions of the random module depend on the basic function random().
  • random() return the next random floating-point number in the range [0.0, 1.0).

   --> random module has a set of methods which are defined below :-


           Bookkeeping functions :


 
random.seed()

Initialize the random number generator.


random.getstate()

Return an object capturing the current internal state of the generator. This object can be passed to setstate() to restore the state.

random.setstate(state)

state should have been obtained from a previous call to getstate(), and setstate() restores the internal state of the generator to what it was at the time getstate() was called.

random.getrandbits(k)

Returns a Python integer with k random bits.

 


Functions for Integers :

random.randrange(stop)
random.randrange(start, stop, step)
   Returns a randomly selected element from the given range.
random.randint(a, b)

Return a random integer N such that a <= N <= b. 

    

Functions for Sequences :


random.choice(seq)

Return a random element from the non-empty sequence seq.  seq is empty will raises to index Error.

random.choices(seq,k=1)

Return a k sized list of elements chosen from the seq. If the seq is empty, raises index Error.

random.shuffle(x[, random])

Take a sequence and returns the sequence in random order.

random.sample(seq, k)

Return a k length list of unique elements chosen from the seq .


Real-valued distributions :

The following functions generate specific real-valued distributions. Function parameters are named after the corresponding variables in the distributions equation, as used in common mathematical practice; most of these equations can be found in any statistics text.

random.random()

Return the next random floating point number in the range [0.0, 1.0).

random.uniform(a, b)

Return a random floating point number N such that a <= N <= b for a <= b and b <= N <= a for b < a.


random.triangular(low, high, mode)

Return a random floating point number N such that low <= N <= high and with the specified mode between those bounds. The low and high bounds default to zero and one. The mode argument defaults to the midpoint between the bounds, giving a symmetric distribution.

random.betavariate(alpha, beta)

Returns a random float number between 0 and 1.Conditions on the parameters are alpha > 0 and beta > 0

random.expovariate(lmbd)

Exponential distribution. lmbd is 1.0 divided by the desired mean. It should be nonzero. (The parameter would be called lambda, but that is a reserved word in Python.) Returned values range from 0 to positive infinity if lmbd is positive, and from negative infinity to 0 if lmbd is negative.

random.gammavariate(alpha, beta)

Gamma distribution. (Not the gamma function!) Conditions on the parameters are alpha > 0 and beta > 0.

random.gauss(mu, sigma)

Gaussian distribution. mu is the mean, and sigma is the standard deviation. This is slightly faster than the normalvariate() function defined below.

random.lognormvariate(mu, sigma)

Log normal distribution. If you take the natural logarithm of this distribution, you get a normal distribution with mean mu and standard deviation sigma. mu can have any value, and sigma must be greater than zero.

random.normalvariate(mu, sigma)

Normal distribution. mu is the mean, and sigma is the standard deviation.

random.vonmisesvariate(mu, kappa)

mu is the mean angle, expressed in radians between 0 and 2*pi, and kappa is the concentration parameter, which must be greater than or equal to zero. If kappa is equal to zero, this distribution reduces to a uniform random angle over the range 0 to 2*pi.

random.paretovariate(alpha)

Pareto distribution. alpha is the shape parameter.

random.weibullvariate(alpha, beta)

Weibull distribution. alpha is the scale parameter and beta is the shape parameter.


Alternative Generator :


class random.Random([seed])

Class that implements the default pseudo-random number generator used by the random module.

class random.SystemRandom([seed])

Class that uses the os.urandom() function for generating random numbers from sources provided by the operating system. Not available on all systems. Does not rely on software state, and sequences are not reproducible. Accordingly, the seed() method has no effect and is ignored. The getstate() and setstate() methods raise NotImplementedError if called.


***Go and visit my next articles to learn more about every random module functions in details***

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