Raising numbers to power **

[GJG]

Hi there!
I've noticed something that I can't quite wrap my head around:
if I raise 2**2 I get 4
and if I raise 4**3 I get 64
but if I do something like 2**2**3 I get 256 ???

Why am I getting this result rather than 64 ?
Thanks !

[deanhystad]

Precedence rules. Is evaluated as 2**(2**3). Always use parenthesis when precedence is unclear, even if they aren't needed. Clarity in code is as important as correctness.

[perfringo]

Another thing to keep in mind that numeric literals in Python are without sign and ** binds more tightly than unary sign. Therefore you must not be surprised by this:

>>> -2**2
-4
>>> (-2)**2
4

[deanhystad]

From the docs

6.5. The power operator
The power operator binds more tightly than unary operators on its left; it binds less tightly than unary operators on its right. The syntax is:

power ::= (await_expr | primary) ["**" u_expr]
Thus, in an unparenthesized sequence of power and unary operators, the operators are evaluated from right to left (this does not constrain the evaluation order for the operands): -1**2 results in -1.

The power operator has the same semantics as the built-in pow() function, when called with two arguments: it yields its left argument raised to the power of its right argument. The numeric arguments are first converted to a common type, and the result is of that type.

For int operands, the result has the same type as the operands unless the second argument is negative; in that case, all arguments are converted to float and a float result is delivered. For example, 10**2 returns 100, but 10**-2 returns 0.01.

Raising 0.0 to a negative power results in a ZeroDivisionError. Raising a negative number to a fractional power results in a complex number. (In earlier versions it raised a ValueError.)