Overview

The midterm exam is comprehensive and will cover the following topics:

1. Basic Syntax and Types

2. Conditional Execution

3. Iteration

4. Functions

5. Lists and Strings

As with the quizzes, the exam will consist of definitions, code evaluation, short answers, translation, debugging, and programming sections. For the programming section, you will be able to use your computer (but only after you have completed all the other sections).

Below are examples of the type of questions that may be asked on the midterm. It is mean to be representative, rather than exhaustive (ie. there may be questions that show up on the midterm that are not show below).

Definitions

Briefly define the following terms.

1. Program:

2. Interpreter:

3. Variable:

4. Syntax Error:

5. Expression:

6. Statement:

7. Boolean Expression:

8. Exception:

9. Short Circuit Evaluation:

10. Infinite Loop:

11. Immutable:

12. Function:

13. Named Argument:

14. Scope:

Code Evaluation

1. What is the result of the each of the following lines of Python code:

   print type(1 + 3)
   print type(1 + 3.0)
   print '1' + 3
   print '1' + '3'
   

2. What is the result of the following Python code:

   x = 1
   y = 2
   z = x + y
   print x, y, z
   x = y
   y = x
   print x, y, z
   

3. What is the result of the following Python code:

   for i in range(0, 10):
       if i < 4:
           continue
       elif i == 7:
           break
       else:
           print i
   print i
   

4. What is the result of the following Python code:

   def pretty_print_string(s, title=False, sort=False):
       if title:
           s = s.title()
       if sort:
           s = ' '.join(sorted(s.split()))
   
       print s
   
   pretty_print_string('python is the best')
   pretty_print_string('python is the best', sort=True)
   pretty_print_string('python is the best', True, True)
   

5. What is the result of the following Python code:

   def filter_numbers(numbers, n):
       results = []
       for number in numbers:
           if not number % n:
               results.append(number)
       return results
   
   for i, v in enumerate(filter_numbers(range(0, 10), 4)):
       print i, v
   

6. What is the result of the following Python code:

   def search(numbers):
       is_found = False
       index    = 0
   
       while index < len(numbers) and not is_found:
           if not numbers[index] % 2 and not numbers[index] % 3:
               is_found = True
           else:
               index += 1
   
       return index, numbers[index]
   
   print search(range(3, 9))
   print search(range(8, 16))
   

Short Answer

1. What is the difference between a while loop and a for loop? Give two examples where we would prefer one over the other.

2. What is the difference between a fruitful function and a void function? How do we make a function fruitful? How would you utilize the outputs of a fruitful function?

3. What is the difference between a list and a string? What can you do with a list that you can't do with a string and vice versa?

4. What is the difference between a global variable and a local variable? Give an example of each.

Translation

1. Convert the following Python code to use a while loop instead of a for loop:

   numbers = [5, 4, 7, 0, 1]
   count   = 0
   
   for number in numbers:
       if number:
           break
       count += 1
   

2. Search: Convert the search function above to use a for loop and to take an additional argument find_all which by default is set to False. If find_all is True then the search function should return a list of all numbers that match the criteria.

Debugging

1. Correct the following Python code:

   volume of sphere = (4/3) math.pi (r^3)
   print volume of sphere
   

2. The Python code below is suppose to count all of the even numbers between 1 and 100 (inclusive) that are also a multiple of 5, but it contains some errors. Identify and fix the errors:

   while i < 100:
       if i % 2 or i % 5:
           total + 1
   print total
   

3. The Python code below is suppose to determine if the given list of numbers is sorted. That is, it should return True if each item in the list is less than the next item. Unfortunately, there are a few errors in the code below. Identify the errors and fix the code.

   def is_sorted(numbers):
       ''' Return whether or not the list of numbers is sorted '''
       for i in numbers:
           if numbers[i] < numbers[i + 1]:
               print 'True'
           else:
               print 'False'
   

Programming

1. Write Python code that requests the base and height of a triangle from the user, computes the area of a triangle, and then prints the result:

   Base? 4
   Height? 2
   The area of a triangle with base 4 and height 2 is 4.
   

2. Given a list of random integers, numbers, write Python code that computes the sum of all the numbers between a and b (inclusive) and prints the resulting total.

3. Write Python code that prints 'Yeah' if a number n is between the values a and b (inclusive). Otherwise, print 'Nope'.

4. Write Python code that generates n random numbers (between 0 and 9), counts the number of odd and even numbers, and then prints out the totals.

5. Write Python code that computes the list of the even numbers between 0 and 100. that are also a multiple of 7.

6. Write Python code that simulates rolling a die until we a 6 and reports how many rolls it took.

7. Write a Python function called read_password:

   def read_password(password, prompt='Password?', max_attempts=3):
       ''' Returns whether or not user has entered the correct password. '''
   

   This function provides the user with the prompt and reads the input from the user. This input is checked against the password. If the user input and the password match, then True is returned. This is attempted max_attempts times and then False is returned if there is no match.

8. Write a Python function called filter_range:

   def filter_range(numbers, a, b):
       ''' Return all numbers between a and b (inclusive) '''
   
   >>> filter_range([7, 1, 5], 0, 5)
   [1, 5]
   

   Given a list numbers and two integers a and b, return a list of all items in numbers that are between a and b (inclusive).

9. Write a Python function called count_word:

   def count_word(text, word, case_sensitive=False):
       ''' Return number of times word appears in text '''
   
   >>> count_word('Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo', 'buffalo')
   8
   
   >>> count_word('Buffalo buffalo Buffalo buffalo buffalo buffalo Buffalo buffalo', 'buffalo', True)
   5
   

   Given a string text and a string word, this function returns the number of times word appears in text. If case_sensitive is True, then letter case must be factored in comparing strings.