Random module not working. ValueError: empty range for randrange() (1,1, 0)

Question

In Python 2.7.1, I import the random module. when I call randint() however, I get the error:

ValueError: empty range for randrange() (1,1, 0) 

This error is caused by an error in the random.py module itself. I don't know how to fix it, not does reinstalling python help. I can't change versions.

can someone please give me code for a working module or tell me what to do?

Solution 1

You called randint like this:

 randint(1,0)

That tells randint to return a value starting as 1 and ending at 0. The range of numbers from 1 to zero is as you surely realize an empty range. Hence the error:

 empty range for randrange()

Solution 2

Trust me, random works just fine. You are calling randint with b < a:

>>> random.randint(1, 0)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "C:\Python27\lib\random.py", line 228, in randint
    return self.randrange(a, b+1)
  File "C:\Python27\lib\random.py", line 204, in randrange
    raise ValueError, "empty range for randrange() (%d,%d, %d)" % (istart, istop
, width)
ValueError: empty range for randrange() (1,1, 0)

randint returns a value between the first argument and the second argument.

Solution 3

random.randint(1, 0) returns an error because whenever you use random.randint(a, b) a must be less than b. Try changing random.randint(1, 0) to random.randint(0, 1) to get a valid result.

Click here for more information about random.randint

Solution 4

If you called randint() by itself, it will most definitely result in an error. You need to provide randint() with a range to choose from. randint(a, b), where a and b are integers, should work, and if it doesn't, your Python installation is broken.

It would also raise an exception if b is less than a. Think of it like you're supplying a range: it would make sense to put the lower bound first, right? So put the smaller bound first.

If you really want to compare your random module with the correct one, the source is at http://svn.python.org/view/python/branches/release27-maint/Lib/random.py?view=markup

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Comments

[Admin]

Pro tip: Just because the random module is at the bottom of the stacktrace, it doesn't have to have caused the error (in fact, that's it's unlikely). As already said, post your code (including stacktrace).

[Lennart Regebro]

Please don't claim module isn't working before reading the documentation.

[John Machin]

Pro tip: Read your stacktrace, your error message, your code, and The Fantastic Manual before you start blaming acts of (God, Gates, Guido, ...); the problem is much more likely to be an act of Goofy.

[bgporter]

Note that the OPs exception is raised whenever b < a

[user551717]

I know that's how you call it. I'm calling it and it throws an error because the random module is corrupt.

[Rafe Kettler]

@user551717 then you should do a diff between your version of the model and the source I posted and see what's up

[Lennart Regebro]

Right, but (1,1, 0) is (a,b+1, b-a+1), so in this case he called it with a=1 and b=0.

[user551717]

okay, thank you. I forgot to add a person to the list of which the length is a before I called it.

[Lennart Regebro]

@user551717: So you are gonna select one item from the list randomly? There is already a function for that in the random module. Please read the documentation. docs.python.org/library/random.html Also note that if you add to the second parameter, randint will give you a random integer between 1 and 1. Ie, it will always return 1.