using sympy to solve(approximate) numeric equations's root (it uses bi-sect method)

findroot.py

In [9]: import sympy

In [11]: from sympy import symbols 

In [12]: x = symbols('x')

In [13]: x
Out[13]: x

In [14]: type(x)
Out[14]: sympy.core.symbol.Symbol

In [15]: y=x**2 - 2

In [16]: y
Out[16]: x**2 - 2

In [17]: from sympy import nsolve

sympy.plot(y,(x,-2,2))
Out[22]: <sympy.plotting.plot.Plot at 0x77ec198>

In [18]: nsolve(y,x,(0,2))
Out[18]: mpf('1.414213562373095')

In [19]: nsolve(y,x,(-2,2)) #it will report error

nsolve(y,x,(-2,0))
Out[20]: mpf('-1.414213562373095')