IT 117: Intermediate Scripting - Answers to Midterm Questions

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

Each of the following questions are worth 4 points.

What string value does Python think of as False in an if statement?
```
the empty string
```
Write the Python expression that gives the value of the first command line argument.
```
sys.argv[1]
```
Write a Python expression that returns the intersection of the sets A and B.
```
A.intersection(B) or B.intersection(A)
```
Write the Python statement you would use to stop execution of a script.
```
sys.exit()
```
What are the entries in a dictionary?
```
key - value pairs
```

What does the + in a regular expression match?

1 or more occurrences of the character that comes before it

Write the Python statement to create an empty dictionary named empty.
```
empty = {}
```

What does the * in a regular expression match?

0 or more occurrences of the character that comes before it

Write the Python expression you would use to get a list of all entries in your current directory.
```
os.listdir('.')
```
What are three things are found in a regular expression?
```
ordinary characters, meta-characters, character classes
```
Can a value appear more than once in a set?
```
no
```
Write the Python statement you would use to change your current directory to your parent directory.
```
os.chdir('..')
```

Can the key in a dictionary entry be any data type?

no. you can only use values that are immutable, that cannot be changed

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

one occurrence of any character, except the newline

Write a Python expression that returns the union of the sets A and B.
```
A.union(B) or B.union(A)
```

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

Write the regular expression which will match each line below.
It should also extract the score and full name from each line.
Assume there are no whitespace characters after the name.
```
100    Bill Smith
85     Jane Doe
9      John Parker
```
I am looking for a SINGLE regular expression that matches all lines.
```
(\d{1,3})\s+(.+)
```
Define the function file_count, which takes dir, a directory pathname, as its only parameter.
The function should count the number of files in the directory dir.
It should go to the directory given by dir.
It should them make a list of all the entries in the directory.
It should then use os.path.isfile() to see if the entry is a file.
If it is, you should increment the count.
It should return the number of files it finds.
```
def file_count(dir):
   os.chdir(dir)
   count = 0
   for entry in os.listdir():
      if os.path.isfile(entry):
         count += 1
   return count
```
Define a function set_create, which takes file, a file object, as its only parameter.
The file contains words, one to a line.
The function should read in each line and strip the line feed.
The file looks like this
```
atom
barn
disk
storm
...
```
It should then add the word to a set.
After reading all the words in a file, it should return the set.
```
def set_create(file):
   s = set()
   for word in file:
      s.add(word.strip())
   return s
```
Define the function temps_dict_create which takes file, a file object, as its only parameter.
The function should read in a file with entries like this
```
1/1/2021 38
1/2/2021 39
1/3/2021 40
...
```
It should use these values to create a dictionary where the keys are dates and the values are temperatures.
You should use the split method on each line to get the date and temperature.
It should then return this dictionary.
```
def temps_dict_create(file):
   temps = {}
   for line in file:
      date, temp = line.split()
      temps[date] = temp
   return temps
```