IT 116: Introduction to Scripting - Answers to Questions on Final Exam

IT 116: Introduction to Scripting
Answers to Questions on Final Exam - Odd Columns

Each of the following questions are worth 3 points.

What are the only values that a boolean expression can have?
```
True and False
```
If you want to stop a Python script running on Unix, what do you do?
```
Control C
```
What do you call the functions that are always available in Python and DO NOT have to be imported?
```
built-in functions
```
What do you call a variable that is defined inside a function?
```
a local variable
```

Name the four types of expressions.

literals, variables, calculations, function calls

What must you create to work with a file in Python?
```
a file object
```
What is the Python function that creates the thing you need to work with a file?
```
open
```

What is a syntax error?

an error caused by code that does not follow the rules of the Python language

What is a logic error?

an error that causes the code to give incorrect results

What is a runtime error?

when a value in a Python statement causes the statement to fail

What permissions does an account need on a Python script to be able to run it without typing the name of the Python interpreter on the command line? I want the NAMES of the permission.
```
read and execute permission
```
What do you all a collection of things stored one right after another?
```
a sequence
```
What is a list?
```
a sequence object that can be changed
```

What is a tuple?

a sequence object that cannot be changed

What operators work with lists?
```
+ and *
```
Write an assignment statement that creates a list of the first 5 integers and assigns it to the variable l1.
```
l1 = [1, 2, 3, 4, 5]
```
Write a Python expression that evaluates to True if the list l1 contains the value 4.
```
4 in l1
```
Write a Python statement to add 6 to the list l1.
```
l1.append(6)
```
Write a Python statement that sorts the list l1.
```
l1.sort()
```
If l1 is a list, what is l2 after the following statement is executed?
```
l2 = l1
```
```
a new list variable pointing to the same list as l1
```

The following questions require you to write code.
Each question is worth 10 points.

Define the function decimal_list_from_file which takes one parameter, file, a file object.
The file is a list of decimal numbers, one to a line, that looks like this
```
56.37
45.133
29.8145
```
The function should convert each line to a float and add it to the list.
It should return that list.
```
def decimal_list_from_file(file):
    list = []
    for line in file:
        list.append(float(line))
    return list
```
Define the function increment_list which takes two parameters, named list and increment.
list points to a list of integers and increment is an integer.
The function should use a for loop to change the list by adding the value of increment to each element.
So if the original list was
```
[1,2,3]
```
and the increment was 2, the list would become
```
[3,4,5]
```
```
def increment_list(list, increment):
    for index in range(len(list)):
        list[index] += increment
```
Define the function average_list which takes one parameter, num_list, a list of integers.
The function should use a loop to add all the numbers and return the average.
This average should be rounded to two decimal points.
```
def average_list(num_list):
    total = 0
    for num in num_list:
        total += num   
    return round(total/len(num_list), 2)
```
Define the function count_chars.
This function takes two parameters, s, a string, and char, a character.
This function should count the number of times char appears in s and return that value.
If the function were called with the arguments s and "o" and s was the string "room" it should return 2.
```
def count_chars(s, char):
    letter_count = 0
    for ch in s:
        if ch  == char:
            letter_count += 1
    return letter_count
```