IT 117: Intermediate Scripting - Answers to Midterm Questions

IT 117: Intermediate Scripting - Odd Columns
Answers to Midterm Questions

Each of the following questions are worth 4 points.

What are the entries in a dictionary?
```
key - value pairs
```
Are dictionaries sequences?
```
no
```
What string value does Python think of as False in an if statement?
```
the empty string
```
Can a value appear more than once in a set?
```
no
```
If we have the sets A and B with the elements below, what are the elements formed by the union of A and B?
```
A = {1, 2, 3}
B = {3, 4, 5}
```
```
{1, 2, 3, 4, 5}
```
Write a Python expression to see if the set s1 contains 5.
```
5 in s1
```
What is the name of the module that allows you to interact with the operating system?
```
os
```
Write the Python expression you would use to get a list of all entries in your current directory.
```
os.listdir('.')
```
What is the name of the module that allows you to interact with the Python interpreter?
```
sys
```
Write the Python expression that gives the value of the first command line argument.
```
sys.argv[1]
```
Write the Python statement you would use to stop execution of a script.
```
sys.exit()
```
What are three things are found in a regular expression?
```
ordinary characters, meta-characters, character classes
```

What does the . (dot) in a regular expression match?

one occurrence of any character, except the newline

What does the + in a regular expression match?

1 or more occurrences of the character that comes before it

What is a greedy match?

a match with the greatest number of characters

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

Define a function named word_frequency.
This function has one parameter, a file object.
This function should read in a file with one word on each line, like the lines below.

   zebra
   baseball
   zebra

The function should return a dictionary where the keys are the words and the values are the number of times the words appear in the file. You should use the following algorithm

create an empty dictionary
for each line in the file
   strip the linefeed from the line
   if the line is already in the dictionary:
      get the count for that word
      increment the count by 1
      assign this new value to the word
   else
      make an entry for the word with the value 1
 return the dictionary

def word_frequency(file):
    words = {}
    for word in file:
        word = word.strip()
        if word in words:
            words[word] += 1
        else:
            words[word] = 1
    return words

Define the function temps_set_create which takes a file object as its only parameter.
The function should read in a file with the minimum and maximum temperatures for each date.
The file will have entries like this
```
1/1/2021    38    41
1/2/2021    39    45
1/3/2021    40    55
...
```
The function should create and return a set of all the MINIMUM temperatures read from this file.
The minimum temperature is the first temperature on each line.
```
def temps_set_create(file):
    temps = set()
    for line in file:
        fields = line.split()
        temps.add(fields[1])
    return temps
```
Define a function named dir_count.
This function has one parameter, a path to a directory.
The function should go to the directory specified by the path.
It should then loop through all the entries in the directory and count the number of directories it finds.
You will need to use the function os.path.isdir().
The function should return the number of directories it finds.
```
def dir_count(path):
    os.chdir(path)
    total_dirs = 0
    entries = os.listdir()
    for entry in entries:
        if os.path.isdir(entry):
            total_dirs += 1
    return total_dirs
```
Write the regular expression which will match each line in the scores file below.
It should also extract the values for the full name and the score.
```
Bill Smith   100
Jane Doe      85     
John Parker    9
```
I am looking for a SINGLE regular expression that matches all lines
```
(\w+\s\w+)\s+(\d+)
```