code: def poisson(x, a, b, c, d=0):
      '''
      Poisson function
      a -> height of the curve's peak
      b -> position of the center of the peak
      c ->  standard deviation 
      d -> offset
      '''
      from scipy.misc import factorial #save startup time
      lamb = 1
      X = (x/(2*c)).astype(int)
      return a * (( lamb**X/factorial(X)) * np.exp(-lamb) ) +f poisson(x, a, b, c, d=0):
      '''
      Poisson function
      a -> height of the curve's peak
      b -> position of the center of the peak
      c ->  standard deviation 
      d -> offset
      '''
      from scipy.misc import factorial #save startup time
      lamb = 1
      X = (x/(2*c)).astype(int)
      return a * (( lamb**X/factorial(X)) * np.exp(-lamb) ) +d
docs: Poisson function
      a -> height of the curve's peak
      b -> position of the center of the peak
      c ->  standard deviation 
      d -> offset