Built in functions in Python 3

Question

First question: I'm looking to do a calculator and wanted to do it without calling math.sqrt. So I look up what the function does and I only found this:
def sqrt(x):
"""Return the square root of x.

:type x: numbers.Real
:rtype: float
"""
return 0.0
Can anyone explain what I'm seeing?
Second question: Generally do people study each and every functions they use or they just accept that it does the job?

Answer 1

Try using x**.5
Does the same job as math.sqrt(x) and you don't have to import the whole math module. That is, if you only need it for the sqrt()

Answer 2

I doubt everyone studies everything. If you use a given module often you learn its functions and study the documentation to understand how you can benefit from it. But then I think you just give in to the flow :)
If you ask me, this is actually the biggest advantage of Python, that you can build on others' codes to minimize the code-building part, so you can focus on the idea.

Answer 3

Oh forgot that I can just use exponents to express roots and their indexes however, I still wonder about the 2nd question.