Sample Midterm 1 Answers

  1. Which of the following Python identifiers are legal variable names? For those that are not, say why not.
    1. x
    2. Celsius
    3. spam3
    4. <hello>
    5. question?
    Answer: Choices a, b, and c are legal variable names. Choice d is not because the characters “<” and “>” are not allowed in variable names; neither is “?”, so choice e is not.
  2. What is the data type (int, long int, float, string, list) of the following:
    1. 3
    2. 3.0
    3. 3L
    4. "hello"
    5. 'x'
    6. [ 1, 2, 3 ]
    Answer:
    1. int
    2. float
    3. long int
    4. string
    5. string
    6. list
  3. Write the following formulas in Python:
    1. convert Fahrenheit to Celsius
    2. 7 × 9
    3. 42
    Answer:
    1. (5.0 / 9.0) * f + 32
    2. 7 * 9
    3. 4 ** 2
  4. What does the following program print?
    for i in "hello":
        print i, "-->", chr(ord(o)+1);
    Answer:
    h --> i
    e --> f
    l --> m
    l --> m
    o --> p
  5. What does the following program print?
    for i in [1, 7, 4]:
        x = (-1) ** i * i;
        print i, x;
    Answer:
    1 -1
    7 -7
    4 4
  6. When I ran the following program:
    x = input("Enter a number: ");
    y = 1.0 / x;
    print "The reciprocal of", x, "is", y;
    I got the following error message:
    Traceback (most recent call last):
      File "test.py", line 3, in <module>
        y = 1 / x;
    ZeroDivisionError: integer division or modulo by zero
    What caused the error? Please be specific.
    Answer: The problem is that there was an attempt to divide by 0. This occurred on line 2. As there is a division by x there, and I entered the value of x in response to the prompt (see line 1), I obviously entered 0.