Python random function

Question

I'm having problems with Python's import random function. It seems that import random and from random import random are importing different things. I am currently using Python 2.7.3

Python 2.7.3 (default, Apr 10 2012, 23:31:26) [MSC v.1500 32 bit (Intel)] on win32
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>>> random()

Traceback (most recent call last):
File "<pyshell#0>", line 1, in <module>
    random()
NameError: name 'random' is not defined
>>> random.randint(1,5)

Traceback (most recent call last):
File "<pyshell#1>", line 1, in <module>
random.randint(1,5)
NameError: name 'random' is not defined
>>> import random
>>> random()

Traceback (most recent call last):
File "<pyshell#3>", line 1, in <module>
random()

TypeError: 'module' object is not callable
>>> random.randint(1,5)
2
>>> from random import random
>>> random()
0.28242411635200193
>>> random.randint(1,5)

Traceback (most recent call last):
File "<pyshell#7>", line 1, in <module>
random.randint(1,5)
AttributeError: 'builtin_function_or_method' object has no attribute 'randint'
>>> 

Answer 1

The random module contains a function named random(), so you need to be aware of whether you have imported the module into your namespace, or imported functions from the module.

import random will import the random module whereas from random import random will specifically import the random function from the module.

So you will be able to do one of the following:

import random
a = random.random()
b = random.randint(1, 5)
# you can call any function from the random module using random.<function>

or...

from random import random, randint   # add any other functions you need here
a = random()
b = randint(1, 5)
# those function names from the import statement are added to your namespace

Answer 2

import random imports the random module, which contains a variety of things to do with random number generation. Among these is the random() function, which generates random numbers between 0 and 1.

Doing the import this way this requires you to use the syntax random.random().

The random function can also be imported from the module separately:

from random import random

This allows you to then just call random() directly.

Answer 3

If you are using PyDev or other clever IDE, make sure it did not import the module automatically, overriding your import. It can be especially confusing here, when module name is equal to a function name, because the error thrown is not a NameError. In my case I added

import random

and later used it:

r = random.radom()

but got:

AttributeError: 'builtin_function_or_method' object has no attribute 'random'

Only after searching I found that PyDev automatically added the line

from random import random

to the end of my imports, so I was in fact calling attribute random of method random. Solution is to delete the automatic import or use it and call the random() method directly.