code: def _sigfigs(n, sigfigs=3):
      'helper function to round a number to significant figures'
      n = float(n)
      if n == 0 or math.isnan(n):  # avoid math domain errors
          return n
      return round(n, -int(math.floor(math.log10(abs(n))) - sigfigs + 1)f _sigfigs(n, sigfigs=3):
      'helper function to round a number to significant figures'
      n = float(n)
      if n == 0 or math.isnan(n):  # avoid math domain errors
          return n
      return round(n, -int(math.floor(math.log10(abs(n))) - sigfigs + 1))
docs: helper function to round a number to significant figures