Comp150 Python Exam 2009

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>>>
orange
>>>

>>> fruit = 'banana'
>>> print fruit[-2]
n
>>>

>>>
I am Alice and I am 10 years old.
>>>

The string format conversion specification '%-5d' % n creates a string that is at most 5 characters wide, is left justified, and contains the number n. The '-' sign indicates left justification, and the '5' specifies the minimum width of the string. Since it is at most 5 characters wide, the string can be less than 5 characters if the number n is smaller.

Using symbolic constants makes code easier to read. Symbolic constants are named values that are assigned to a constant variable. By using symbolic constants, it becomes easier to understand the purpose and meaning of the values used in the code. It also improves code readability by providing descriptive names rather than using literal values.

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>>>
[1, 4, 9, 16, 25]
>>>

>>>
['Hello', 2, 3, 4, 5]
>>>

The function definition allows for two optional parameters: prompt and convert. In the given answer, only the first call to read_value_type, "x", is a valid call because it does not provide any arguments and uses the default values for both prompt and convert. The other calls, "y" and "z", provide arguments for the prompt parameter but do not provide an argument for the convert parameter, which would result in an error.

>>>
12
>>>

>>>
3 4 5
>>>

A namespace is a syntactic container which permits the same name to be used in different modules or functions. It helps avoid naming conflicts and allows for better organization of code.

Random access memory (RAM) is volatile, meaning that its contents are lost when power is turned off or interrupted. A hard drive is an example of non-volatile memory, as the data stored on it remains even when power is removed. Data on non-volatile storage, such as a hard drive, is stored in named locations called files. Therefore, the statements x, y, and z are all true.

The given answer is incorrect. The correct answer is "variable". In Python, "variable" is not a basic type. Instead, it is a placeholder used to store values of different types such as bool, float, and list. The other options mentioned (bool, float, and list) are indeed basic types in Python.

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>>>
>>> var1 = 10
>>> var2 = 5
>>> var3 = 7
>>> (var1 True
>>> (var2 False
>>> (var2 False
>>> ((var15))
False
>>>

The output of the code is "Hellothere". This is because the code is concatenating the strings stored in the variables x and y using the + operator. The result is the combination of the two strings, resulting in "Hellothere".

>>>
>>> varl = True
>>> var2 = False
>>> var3 = True
>>> varl and (var2 or var3) and (not var2)
True
>>> varl or var2
True
>>> not (varl or var2)
False
>>> varl and (var2 or var3)
True
>>>

>>> Hello Goodbye >>>

>>>
>>> 5 == 5 and 5 == 6
False
>>> 5 == 6 or 5 == 5
True
>>> 25%2 == 10%3
True
>>> 'compl50' == 'easy'
False
>>>

The correct answer is "x and y". In procedural programming, the focus is on writing functions that operate on data. In object-oriented programming, the focus is on the creation of objects that contain both data and functionality together. Therefore, both statements x and y are true.

>>>
[4, 5, 6]
>>>

The variable "programs" will contain a list of names of all files ending in '.py' in the current working directory. This is because the "glob.glob" function is used to find all files matching a specific pattern, in this case, '*.py'. The function returns a list of file names that match the pattern, and this list is assigned to the variable "programs".

>>>
B_a_n_a_n_a
>>>

>>>

Traceback (most recent call last):
File "/Users/imac/OneDrive/OneDriveBusiness/COMP150/Previous Exams/Untitled.py", line 2, in
items[0] = -1
TypeError: 'tuple' object does not support item assignment
>>>

>>>
0
>>> $ python argv.py 3 4 5
SyntaxError: invalid syntax
>>>

>>>
5
>>>

>>>
False True
>>>

>>>
20 50 20 50
>>>

Tuples are more efficient to use than lists because tuples are immutable, meaning they cannot be changed once created. This immutability allows tuples to be accessed and processed faster than lists. Tuple assignment is an example of poor programming style because it can make the code less readable and harder to understand. Tuples can be used as dictionary keys because they are hashable, unlike lists which are mutable and cannot be used as keys in a dictionary. Therefore, the correct answer is x and y.

>>>
set(['a'])
>>>

>>> fruit = 'banana'
>>> print fruit [2]
n
>>>

>>>

Traceback (most recent call last):
File "/Users/imac/OneDrive/OneDriveBusiness/COMP150/Previous Exams/Untitled.py", line 2, in
fruit[0] = 'B'
TypeError: 'str' object does not support item assignment
>>>

>>>
Zebra comes before aardvark
>>>

fruit = 'banana'
n = 0
for char in fruit:
if char==' a':
n += 1
else:
n -= 1
print n


>>>
-6
>>>

>>> print max(3, 1, abs(-11), 7, 16-10)
11
>>>

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The correct answer is x. This is because the code fragment is binding the function do_something to the event caused by the user pressing the k key. This means that whenever the user presses the k key, the function do_something will be executed.

The code provided creates a ball on a canvas and uses a while loop to continuously update the position of the ball. The initial position of the ball is set to (10, 10), and it moves across and down the canvas with a step size of 1 in both the x and y directions. The loop runs for 100 iterations, and each time it updates the position of the ball by adding the step size to the current position. Therefore, the ball slowly moves across and down the canvas until it comes to rest at the position (109, 109).

def print_twice(phrase):
print phrase, phrase

def print_four_times(phrase):
print_twice(phrase +phrase)

print_twice('there')




>>>
there there
>>>

The correct answer is w and x. This means that in regards to unit testing, it is true that you can't test a function if you don't know what the output should be (w), and unit testing guarantees the correctness of a function (x).

The code defines a function called collatz_sequence that takes a number n as input. It then enters a while loop that continues until n is equal to 1. Inside the loop, it prints the current value of n. If n is divisible by 2, it updates n to be n divided by 2. Otherwise, it updates n to be n multiplied by 3 and then added by 1.

When collatz_sequence(5) is called, the output will be 5 16 8 4 2. This is because 5 is not divisible by 2, so it is updated to be 5 multiplied by 3 and then added by 1, resulting in 16. 16 is then divided by 2 to give 8, and so on until n becomes 1.

The code defines a function called countdown that takes an argument n. Inside the function, there is a while loop that continues as long as n is greater than or equal to 0. Inside the loop, it prints the value of n and then subtracts 1 from it. After the loop, it prints the final value of n.

When the countdown function is called with an argument of 5, it will print the numbers 5, 4, 3, 2, 1, and then the final value of n which is 0. Therefore, the output of the code is "1 2 3 4 5 0".

The given code `x = x + 1` does not involve any conditional statements or comparisons. Therefore, it does not return a boolean value like True or False. Instead, it increments the value of the variable `x` by 1. Hence, the answer "This code always returns False" is incorrect. The correct explanation is that the code increments the value of `x` by 1.

The statement "x" is true because the function say_hi is the callback that gets called when the hello_button is pressed. However, the statements "y" and "z" are false. The message "hi there" is not output to the console when the hello_button is pressed (statement "y"), and a dialog box with the message "hi there" is not popped up when the hello_button is pressed (statement "z").

>>>
>>> n = 99
>>> if 0 print 'n is a positive single digit'


n is a positive single digit
>>> if 0 print 'n is a positive single digit'


>>> if 0 < n < 10:
print 'n is a positive single digit'


>>> n = -99
>>> if 0 print 'n is a positive single digit'


>>> if 0 print 'n is a positive single digit'


>>> if 0 print 'n is a positive single digit'


>>>

5.6. Programming with style
Readability is very important to programmers, since in practice programs are read and modified far more often than they are written. All the code examples in this book will be consistent with the Python Enhancement Proposal 8 (PEP 8), a style guide developed by the Python community.

We’ll have more to say about style as our programs become more complex, but a few pointers will be helpful already:

use 4 spaces for indentation
imports should go at the top of the file
separate function definitions with two blank lines
keep function definitions together
keep top level statements, including function calls, together at the bottom of the program

>>>
2 2 4 4 2
>>>

>>>
A A
>>>