Calculation error with pow operator
What should print (-2 ** 2)
return? According to my calculations it should be 4
, but interpreter returns -4
.
Is this Python's thing or my math is that terrible?
According to docs, **
has higher precedence than -
, thus your code is equivalent to -(2 ** 2)
. To get the desired result you could put -2
into parentheses
>>> (-2) ** 2
4
or use built-in pow
function
>>> pow(-2, 2)
4
or math.pow
function (returning float
value)
>>> import math
>>> math.pow(-2, 2)
4.0
The **
operation is done before the minus. To get the results expected, you should do
print ((-2) ** 2)
From the documentation:
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
.
A full detail of operators precedence is also available in the documentation. You can see the last line is (expr)
which force the expr to be evaluated before being used, hence the result of (-2) ** 2 = 4
you can also use math library...
math.pow(-2,2) --> 4
-math.pow(2,2) --> -4
math.pow(4,0.5) --> 2