Python - math.prod()-CodePudding

I'm having trouble with the following code:

for x in range(13):
   prod(random.SystemRandom().random() for x in range(8))

What exactly does the "for x in range(8)" do in the prod function? I've read the math documentation but I still don't get it. Can someone explain this function?

CodePudding user response：

This is nothing specific to math.prod(). That's a generator expression that produces a sequence of random numbers. It produces 8 of them because of for x in range(8).

The argument to math.prod() is an iterable, and a generator is one type of iterable. prod() multiplies all the values in the iterable sequence.

CodePudding user response：

for x in range(8) is just part of a generator expression, it has nothing to do with math.prod. To answer your question, it creates a sequence of eight random numbers on the interval [0, 1]. You may see this by

import random

list(random.SystemRandom().random() for x in range(8))

[0.003455723936271693, 0.6805747786326888, 0.546261218098562, 0.601146820744067, 0.8435991971789742, 0.9648570965040333, 0.28307143225490927, 0.4388989719001757]

Using the variable name x is bad practice here because it shadows the x in for x in range(13). The established convention for an unused variable is to name it _. A better implementation of this code is:

from math import prod
import random

for x in range(13):
    prod(random.SystemRandom().random() for _ in range(8))

CodePudding user response：

Not sure if you asking about the syntax or step through.

The range function returns a sequence of numbers starting at 0 going up to to the input you specify.

As this is written it will take the product of 9 random numbers between 0 and 1.

prod(random.SystemRandom().random() for x in range(8))

Because you have it in a loop (for x in range(13)) it will do this 14 times.

for x in range(13):
   prod(random.SystemRandom().random() for x in range(8))

If your question is about list comprehension you can read about it in the python docs