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Date: Mon, 1 Apr 2013 09:28:17 +1100
Subject: Re: Why does 1**2**3**4**5 raise a MemoryError?
From: Chris Angelico <rosuav@gmail.com>
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On Mon, Apr 1, 2013 at 9:06 AM, Alex <foo@email.invalid> wrote:
> Dave Angel wrote:
>
>> On 03/31/2013 02:56 AM, morphex wrote:
>> > > > > 1**2
>> > 1
>> > > > > 1**2**3
>> > 1
>> > > > > 1**2**3**4
>> > 1L
>> > > > > 1**2**3**4**5
>> > Traceback (most recent call last):
>> >   File "<stdin>", line 1, in <module>
>> > MemoryError
>> > > > >
>> >
>> > Does anyone know why this raises a MemoryError?  Doesn't make sense
>> > to me.
>>
>> Perhaps you didn't realize that the expression will be done from
>> right to left.
>
> Really?
>
> The Python 3 documentation
> (http://docs.python.org/3/reference/expressions.html) says in section
> 6.14 (Evaluation order) that "Python evaluates expressions from left to
> right" (an exception being when evaluating assignments, in which case
> the RHS of the assignment is calculated first, in left-to-right order).
>
> Section 6.4 discusses the power operator specifically and does not
> contradict 6.14 except that the power operator uses right-to-left
> evaluation in the presence of unparenthesized unary operators.

http://docs.python.org/3/reference/expressions.html#operator-precedence

Opening paragraph, "... exponentiation, which groups from right to
left". It follows the obvious expectation from mathematics. (The OP is
using Python 2, but the same applies.)

ChrisA