Very new to Python

[bliengme]

This was copied from a book but gives several errors. Help!

from math import exp
def bisection(f,a,b,tol= 1e-3):
  if f(a)*f(b) > 0:
     print(f"No roots or more than one root in [{a},{b}]")
     return

     m = (a+b)/2

  while abs(f(m)) > tol:
     if f(a)*f(m) < 0:
        b = m
     else:
        a = m
        m = (a+b)/2
  return m

#call the method for f(x)= x**2-4*x+exp(-x)
f = lambda x: x**2-4*x+exp(-x)
sol = bisection(f,-0.5,1,1e-6)

print(f"x = {sol:g} is an approximate root, f({sol:g}) = {f(sol):g}")