Python

I wouldn't worry about the random argument or use it in any new code as it has been deprecated in Python 3.9:

random.shuffle(x[, random])

Shuffle the sequence x in place.

The optional argument random is a 0-argument function returning a random float in [0.0, 1.0); by default, this is the function random().

...

Deprecated since version 3.9, will be removed in version 3.11: The optional parameter random.

If you are interested in how it works anyway here is the actual source code that makes it pretty clear:

def shuffle(self, x, random=None):
        """Shuffle list x in place, and return None.
        Optional argument random is a 0-argument function returning a
        random float in [0.0, 1.0); if it is the default None, the
        standard random.random will be used.
        """

        if random is None:
            randbelow = self._randbelow
            for i in reversed(range(1, len(x))):
                # pick an element in x[:i+1] with which to exchange x[i]
                j = randbelow(i + 1)
                x[i], x[j] = x[j], x[i]
        else:
            _warn('The *random* parameter to shuffle() has been deprecated\n'
                  'since Python 3.9 and will be removed in a subsequent '
                  'version.',
                  DeprecationWarning, 2)
            floor = _floor
            for i in reversed(range(1, len(x))):
                # pick an element in x[:i+1] with which to exchange x[i]
                j = floor(random() * (i + 1))
                x[i], x[j] = x[j], x[i]