How do I calculate square root in Python?

Question

sqrt=x**(1/2) is doing integer division. 1/2 == 0.

So you're computing x^(1/2) in the first instance, x⁽⁰⁾ in the second.

So it's not wrong, it's the right answer to a different question.

You have to write: sqrt = x**(1/2.0), otherwise an integer division is performed and the expression 1/2 returns 0.

This behavior is "normal" in Python 2.x, whereas in Python 3.x 1/2 evaluates to 0.5. If you want your Python 2.x code to behave like 3.x w.r.t. division write from __future__ import division - then 1/2 will evaluate to 0.5 and for backwards compatibility, 1//2 will evaluate to 0.

And for the record, the preferred way to calculate a square root is this:

import math
math.sqrt(x)

import math
math.sqrt( x )

It is a trivial addition to the answer chain. However since the Subject is very common google hit, this deserves to be added, I believe.

/ performs an integer division in Python 2:

>>> 1/2
0

If one of the numbers is a float, it works as expected:

>>> 1.0/2
0.5
>>> 16**(1.0/2)
4.0

What you're seeing is integer division. To get floating point division by default,

from __future__ import division

Or, you could convert 1 or 2 of 1/2 into a floating point value.

sqrt = x**(1.0/2)