old_contents: import math
  
  def distance(x,y):
      """[summary]
      HELPER-FUNCTION
      calculates the (eulidean) distance between vector x and y.
  
      Arguments:
          x {[tuple]} -- [vector]
          y {[tuple]} -- [vector]
      """
      assert len(x) == len(y), "The vector must have same length"
      result = ()
      sum = 0
      for i in range(len(x)):
          result += (x[i] -y[i],)
      for component in result:
          sum += component**2
      return math.sqrt(sum)
      
  
  def nearest_neighbor(x, tSet):
      """[summary]
      Implements the nearest neighbor algorithm 
  
      Arguments:
          x {[tupel]} -- [vector]
          tSet {[dict]} -- [training set]
      
      Returns:
          [type] -- [result of the AND-function]
      """
      assert isinstance(x, tuple) and isinstance(tSet, dict)
      current_key = ()
      min_d = math.inf
      for key in tSet:
          d = distance(x, key)
          if d < min_d:
              min_d = d
              current_key = key
      return tSet[current_key]
new_contents: import math
  
  def distance(x,y):
      """[summary]
      HELPER-FUNCTION
      calculates the (eulidean) distance between vector x and y.
  
      Arguments:
          x {[tuple]} -- [vector]
          y {[tuple]} -- [vector]
      """
      assert len(x) == len(y), "The vector must have same length"
      result = ()
      sum = 0
      for i in range(len(x)):
          result += (x[i] -y[i],)
      for component in result:
          sum += component**2
      return math.sqrt(sum)
  
  
  def nearest_neighbor(x, tSet):
      """[summary]
      Implements the nearest neighbor algorithm
  
      Arguments:
          x {[tupel]} -- [vector]
          tSet {[dict]} -- [training set]
  
      Returns:
          [type] -- [result of the AND-function]
      """
      assert isinstance(x, tuple) and isinstance(tSet, dict)
      current_key = ()
      min_d = float('inf')
      for key in tSet:
          d = distance(x, key)
          if d < min_d:
              min_d = d
              current_key = key
      return tSet[current_key]
  
subject: Replace min.inf by float(inf)