In python, what is the difference between random.uniform() and random.random()?

Question

In python for the random module, what is the difference between random.uniform() and random.random()? They both generate pseudo random numbers, random.uniform() generates numbers from a uniform distribution and random.random() generates the next random number. What is the difference?

Have you read [the documentation](https://docs.python.org/2/library/random.html)? `random.uniform(0, 1)` is the same as `random.random()`. — jonrsharpe, May 04 '15 at 12:53
There is a difference, due to floating-point rounding you can sometimes hit the upper bound in uniform — Padraic Cunningham, May 04 '15 at 12:56
Actually according to the documentation they are not the same... — Roman Kutlak, May 04 '15 at 12:57

score 99 · Answer 1 · edited Aug 29 '17 at 08:18

random.random() gives you a random floating point number in the range [0.0, 1.0) (so including 0.0, but not including 1.0 which is also known as a semi-open range). random.uniform(a, b) gives you a random floating point number in the range [a, b], (where rounding may end up giving you b).

The implementation of random.uniform() uses random.random() directly:

def uniform(self, a, b):
    "Get a random number in the range [a, b) or [a, b] depending on rounding."
    return a + (b-a) * self.random()

random.uniform(0, 1) is basically the same thing as random.random() (as 1.0 times float value closest to 1.0 still will give you float value closest to 1.0 there is no possibility of a rounding error there).

score 11 · Answer 2 · answered Nov 15 '16 at 09:34

In random.random() the output lies between 0 & 1 , and it takes no input parameters

Whereas random.uniform() takes parameters , wherein you can submit the range of the random number. e.g.
import random as ra print ra.random() print ra.uniform(5,10)

OUTPUT:-
0.672485369423 7.9237539416

score 11 · Answer 3 · answered Dec 17 '18 at 14:43

11

Apart from what is being mentioned above, .uniform() can also be used for generating multiple random numbers that too with the desired shape which is not possible with .random()

np.random.seed(99)
np.random.random()

#generates 0.6722785586307918

while the following code

np.random.seed(99)
np.random.uniform(0.0, 1.0, size = (5,2))

#generates this 
array([[0.67227856, 0.4880784 ],
       [0.82549517, 0.03144639],
       [0.80804996, 0.56561742],
       [0.2976225 , 0.04669572],
       [0.9906274 , 0.00682573]])

This can't be done with random(...), and if you're generating the random(...) numbers for ML related things, most of the time, you'll end up using .uniform(...)

answered Dec 17 '18 at 14:43

Daksh Gupta

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This is for numpy's random module, which is different than the Python stdlib's random module. Still, very useful to know! – Michael Scott Asato Cuthbert Jun 12 '22 at 00:19
What is np in this code? Also, I tried using `random.uniform(0.0, 1.0, size = (5,2))` and was given an error that size was an unexpected keyword argument. – Sabatino Ognibene Feb 16 '23 at 20:52

score 6 · Answer 4 · answered May 04 '15 at 12:57

6

The difference is in the arguments. It's very common to generate a random number from a uniform distribution in the range [0.0, 1.0), so random.random() just does this. Use random.uniform(a, b) to specify a different range.

answered May 04 '15 at 12:57

Bill the Lizard

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score 2 · Answer 5 · answered May 04 '15 at 12:57

According to the documentation on random.uniform:

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

while random.random:

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

I.e. with random.uniform you specify a range you draw pseudo-random numbers from, e.g. between 3 and 10. With random.random you get a number between 0 and 1.

In python, what is the difference between random.uniform() and random.random()?

5 Answers5

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