[issue43628] Incorrect argument errors for random.getstate()

[Raymond Hettinger]

Raymond Hettinger <raymond.hettinger at gmail.com> added the comment:

Here's how to use getstate() and setstate():

>>> import random
>>> state = random.getstate()
>>> random.choices('ABCDE', k=8)
['E', 'A', 'B', 'B', 'A', 'A', 'E', 'D']
>>> # restore the previous state
>>> random.setstate(state)
>>> # now, replay the random selections
>>> random.choices('ABCDE', k=8)
['E', 'A', 'B', 'B', 'A', 'A', 'E', 'D']



> 1. Is the TypeError correct? This should be an inconsistent
> argument number error. There is nothing to do with Type. 

Yes, it is correct, but I agree that it is unintuitive.  It just happens to be the Python way to report an incorrect number of arguments as a TypeError.


> 2. Is the detailed error correct? Doc says random.getstate()
> takes 0 argument, the reported error says getstate() take 1
> positional argument. which is inconsistent. 

This is an artifact of how Python implements object orient programming.  No one really likes this, but at some level it can be viewed as being technically correct — methods prepend an instance argument before calling an underlying function which reports on the number of arguments that it sees.  Presumably, if there were a straight-forward way of improving the error message, it would have been done long ago.

> Besides, I pass one argument to random.getstate(), 
> but the reported error says 2 were given.

Don't pass any arguments into getstate().


> random.getstate() takes 0 argument and return 
> the current setting for the weekday to start each week.

This part doesn't make sense to me.  Why do you think it accepts or returns a weekday?

----------
resolution:  -> not a bug
stage:  -> resolved
status: open -> closed

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Python tracker <report at bugs.python.org>
<https://bugs.python.org/issue43628>
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