CSCI 150 HW 5: while loop, string, and list reading practice

Due: Wednesday, March 2

To receive full credit, for each exercise you should do the following:

1. Predict: First, complete the exercise without using the Python interpreter. (You are welcome to refer to your notes or textbook, read Python documentation, look at examples from class, etc.; just don't actually run any code.) Write down what you think the output will be. Most likely you will need to write down some intermediate work to keep track of values of variables; feel free to include that work as well.

2. Check: Run the code. Does the actual output agree with what you wrote down in step 1?

3. Evaluate: If your answer to part 1 was different than the actual output, keep experimenting with it, consult the textbook or Python documentation, ask a friend or TA or professor, etc. until you can explain why the code works the way it does and what your misunderstanding(s) were in part 1. (You do not need to do anything for step 3 if the output agrees exactly with what you wrote in step 1.)

You will not be graded on how correct your answer is in part 1. However, you will be graded on the accuracy of your evaluation in step 3. Obviously, I will not be able to tell the difference if you simply run the code and paste the output for step 1; please do not do that! You will only be depriving yourself of a learning opportunity (not to mention that it is a violation of the academic integrity policy).

Turn in your answers and evaluations either electronically on Moodle, or on paper.

You should consider the code in each exercise separately from the other exercises.

1. Consider the following code. What is printed by the final line, print mklist(5)?

   def mklist(n):
       nums = []
       i = 0
       p = 1
       while (i <= n):
           nums.append(p)
           p *= 2
           i += 1
       return nums
   
   print mklist(5)

2. What is printed by the following code?

   animals = ['caiman', 'bat', 'dingo', 'chihuahua', 'baboon', 'fox', 'galapagos']
   
   i = 0
   while i < len(animals):
       if (animals[i][1] == 'a'):
           print animals[i]
   
       i += 1

3. What is printed by the following code?

   s = 'thesethickthornythistlethingsthrivethroughoutthethicket'
   
   pos = 0
   while pos != -1:
       next = s.find('th',pos+1)
       if next != -1:
           print s[pos:next]
       else:
           print s[pos:]
       pos = next