CODEWITHSUNDEEP
pythonpython-3.xmathoperators
lontivero
lontivero

Reputation: 5275

Why is -2**2 == -4 but math.pow(-2, 2) == 4.0?

Why are not these two statements equivalents?

>> math.pow(-2,2)
4.0
>> -2 ** 2
-4

Python 3.5.3 (default, Jan 19 2017, 14:11:04)

Upvotes: 6

Views: 299

Answers (3)

Hejun
Hejun

Reputation: 376

because the precedence of '-' is behind the precedence of '**', use (-2)**2 to calculate -2 at first

Upvotes: 1

ABcDexter
ABcDexter

Reputation: 2941

You can check the precedence from the Python3 documentation.

-2**2

calculates as : -(2**2) = -4.

Upvotes: 1

Reblochon Masque
Reblochon Masque

Reputation: 36742

The order of execution of the operators (operator precedence) matters here: with -2**2, the exponentiation of 2 to the power 2 is first executed, then the negative sign.

Use parenthesis to obtain the desired result

(-2)**2 = 4

Upvotes: 7

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