Square root.

There are a bunch of built-in functions that you can use in your programs.  
You have to "import" the appropriate "module".  
Here's how the sqrt function can be used:

import math

x = eval(input("Enter a number: "))
y = math.sqrt(x)
print("Square root of that number is", y)

The value of x is the value that will be square rooted.  The "call" of
the sqrt function evaluates to (sort of becomes) the square root of x,
which is then assigned to be the value of y.

print("square root of 2 is",math.sqrt(2))

Square root is the same as raising to the half power:

print("square root of 2 is",2**(1/2))

but the preferred style is to use the sqrt()