Compsci 06, Spring 2011, Test 2 Practice, April 11

Name____________________   net-id _________       

Name____________________   net-id _________       

Name____________________   net-id _________

In writing code to store the names of students on the wait-list for a course the programmer uses a list instead of a set. What's a good reason to use a list for this task (rather than a set)?
Which statement creates a list of the elements in common to two lists a and b. More than one can be correct.
1. list(set(a)&set(b))
2. [x for x in a if x in b]
3. [x for x in set(a) if x in set(b)]
Two lists are given:
```
 x = [1,2,3]
 y = [5,6,7]
```
What is the value of [(a,y[i]) for i,a in enumerate(x)]
1. [(1,5), (2,6), (3,7)]
2. [(5,1), (6,2), (7,3)]
3. [(0,5), (1,6), (2,7)]
What is the value of [(a,b) for a in x for b in y]?
1. [(1,5), (2,6), (3,7)]
2. [(1,5),(1,6),(1,7),(2,5),(2,6),(2,7),(3,5),(3,6),(3,7)]
3. [(1,7), (2,6), (3,5)]
The list comprehension [x for x in range(100) if x % 3 == 0] represents the list [0,3,6,...,96,99], i.e., multiples of three less than 100. Write a list comprehension for multiples of seven between 500 and 600 (inclusive).
Write a list comprehension for perfect squares less than 500, i.e., [0,1,4,9,16,25,...,441,484]
Data for student groups at Duke is stored in a file as below:
```
Duke Chronicle:svp9,tlm,fro72
Student Government:tlm,ola,ezp9
Ski Club: fro72, frp9, tlm,ght
```
Each group/club is the first part of a line, followed by a colon, followed by the net-ids of those in the group/club. Write a function that has a filename as a parameter and which returns a dictionary in which keys are net-ids/strings and the associated value is a list of organizations to which the person with the net-id belongs to. For example in the file above:
```
   tlm : ["Duke Chronicle", "Student Government", "Ski Club"]
```
Complete the function below:
```
  def groups(filename):
      """
      filename is name of a file in proper format
      returns dictionary with net-id as key and value
      a list of groups/organizations
      """

      f = open(filename):
      





















      close(f)
```