Python Forum

from random import sample

sample(range(2 ** 63 - 1), 3) # OK
sample(range(2 ** 63), 3) # OverflowError

Error:
Traceback (most recent call last):
  File "c:\...\test.py", line 4, in <module>
    sample(range(2 ** 63), 3) # OverflowError
  File "C:\Users\...\AppData\Local\Programs\Python\Python38\lib\random.py", line 361, in sample
    n = len(population)
OverflowError: Python int too large to convert to C ssize_t

Documentation of random.sample

Quote:random.sample(population, k)
Return a k length list of unique elements chosen from the population sequence or set. Used for random sampling without replacement.

Returns a new list containing elements from the population while leaving the original population unchanged. The resulting list is in selection order so that all sub-slices will also be valid random samples. This allows raffle winners (the sample) to be partitioned into grand prize and second place winners (the subslices).

Members of the population need not be hashable or unique. If the population contains repeats, then each occurrence is a possible selection in the sample.

To choose a sample from a range of integers, use a range() object as an argument. This is especially fast and space efficient for sampling from a large population: sample(range(10000000), k=60).

If the sample size is larger than the population size, a ValueError is raised.

OverflowError will be raised if the population size is larger than (2 ** 63 - 1).

Python version: 3.8.1
OS: Windows 10 pro 1909 (18363.592)

so what is your question?

(Jan-28-2020, 07:03 PM)buran Wrote: [ -> ]so what is your question?

I don't think OverflowError should be raised in this case.
Just because population size can't convert to a 64-bit signed integer? (Even so, why not 'unsigned'?)
The documentation didn't mentioned that 'sample' method has this limit.

---

This error is caused by 'len(range(n))':

len(range(2 ** 63 - 1)) # OK
len(range(2 ** 63)) # OverflowError

Error:
Traceback (most recent call last):
  File "c:\Users\...\test.py", line 6, in <module>
    len(range(2 ** 63))
OverflowError: Python int too large to convert to C ssize_t

Why 'len(range(n))' has this limit?
Is this a bug?

sys.maxsize():

Quote:An integer giving the maximum value a variable of type Py_ssize_t can take. It’s usually 2**31 - 1 on a 32-bit platform and 2**63 - 1 on a 64-bit platform.

Look also at PEP237 - Unifying Long Integers and Integers

(Jan-29-2020, 06:07 AM)perfringo Wrote: [ -> ]sys.maxsize():

Quote:An integer giving the maximum value a variable of type Py_ssize_t can take. It’s usually 2**31 - 1 on a 32-bit platform and 2**63 - 1 on a 64-bit platform.

Look also at PEP237 - Unifying Long Integers and Integers

Thanks for your help. The documentation of range also explained the problem.

Quote:Ranges containing absolute values larger than sys.maxsize are permitted but some features (such as len()) may raise OverflowError.