Lab Quiz 4 – Comments and Solutions

\(\boxdot\) Problem 7

• The most common form of a solution:

  def alpha_stack(s1, s2):
     s3 = ''
     if len(s1) != len(s2):
         return 'Sorry, the strings must be the same length.'
     for i in range(len(s1)):
         if s1[i] < s2[i]:
             s3 += s1[i]  
         else:  
             s3 += s2[i]  
     return s3  

• A fewer lines solution using list comprehension:

  def alpha_stack(s1, s2):
      if len(s1) != len(s2):
          return 'Sorry, the strings must be the same length.'
      return ''.join([min(s1[i], s2[i]) for i in range(len(s1))])

\(\boxdot\) Problem 8

• Using a while loop:

  def int_list(n):
      new_l = []
      while sum(new_l) < 100 and len(new_l) < n:
          new_l.append(random.rand(1,76))  
      return new_l  

• Another common solution without using a while loop:

  def int_list(n):
      new_l = []
      for i in range(n):
          new_l.append(random.rand(1,76))
          if sum(new_l) >= 100:
              return new_l
      return new_l  

\(\boxdot\) General Comments

• Pay attention to what must be returned, is it a list, string, Boolean, … ?

• Do not re-reference any parameters

  def alpha_stack(s1, s2):
      s1 = 'cat'  
      s2 = 'dog'  

• Initialize a variable before accumulating

• Cannot traverse (use a range() function) on an int object

• Adding to a list object:

  l1 = [1, 2, 3, 4]  
  l2 = l1 + [5] = [1, 2, 3, 4, 5]  
  l1.append(5) = [1, 2, 3, 4, 5]  
  l1.append([5]) = [1, 2, 3, 4, [5]]