Name:
Directions: Work only on this sheet (on both
sides, if needed); do not turn in any supplemen-
tary sheets of paper. There is actually plenty of
room for your answers, as long as you organize
yourself BEFORE starting writing. In order to
get full credit, SHOW YOUR WORK.
1. (15) Which of the following would be legal/illegal if in-
serted into the program tfe.py in Sec. 5.1 of our Python
tutorial PLN? Write “legal” or “illegal.” Each is indepen-
dent of the others, i.e. you are not being asked whether it
would be legal to insert more than one of them together.
(a) : b.idnum = 1 after line 23
(b) : w = a.name + b.name after line 23
(c) : b = 12 after line 27 (not indented)
2. (10) Suppose an exception occurs which our program
does not handle using try...except. The name of the de-
fault function which is called at that time is .
3. (10) Write a single line of code which produces cmdl-
nargs, a list consisting of all the command-line argu-
ments excluding the name of the program being run.
(Note: Code like if x == y: z = 8 counts as two lines,
as if the second part were on a new line.)
4. (10) In our Python network programming PLN, we
didn’t call an analog of the function gethostbyname()
seen in our network tutorial PLN, because that function’s
actions are included in the Python function .
Similarly, the information returned by getpeername()
in the network tutorial is included in what is returned by
the Python function .
5. (15) Fill in the blanks in the following pair of func-
tions which find all files of a given name (regardless of
whether they be ordinary files, directories or links) in a
given directory tree. Each file is reported in terms of the
path relative to dtroot. Example: The tree starts at
/z/a, which contains an ordinary file band a directory
c; the latter contains a directory b; the program is run
from within c, with ‘..’ as dtroot and ‘b’ as targetfile.
Then the output will be
../b
../c/b
Here is the code:
import os, sys
def checkthisdir(targetfile,dr,flst):
if ____________________:
print os.path.join(____________________)
def findfile(dtroot,targetfile):
os.path.walk(________________________)
6. (20) Fill in the blanks in the following lines of code,
which returns a list of all words in a text file. It is pre-
sumed that the file has already been opened by the calling
program, with fibeing assigned the result of open(), but
no other operations have been performed on the file.
def getwords(fi):
wrds = map(________________________)
return reduce(________________)
For example, if called on the file
a b cd
xyz
uu vv
the value returned should be [’a’, ’b’, ’cd’, ’xyz’, ’uu’,
’vv’].
7. (20) Suppose you are debugging a multi-module pro-
gram by using pdbw.py. You wish to know how many
breakpoints you’ve set in each module. You will be able
to do so using a module bpl.py. For example, in debug-
ging our example of tf.py and tftest.py in Sec. 9.1.1 of
our Python tutorial PLN, we might have:
(Pdb) import bpl
(Pdb) bpl.bpc(debugger)
/a/b/tf.py 2
/a/b/tftest.py 1
Fill in the blanks in bpl.py:
def bpc(dbg):
for f in ____________________:
print f, ____________________
Solutions:
1.a Legal. Classes are implemented as dictionaries, and
thus can be added to at any time.
1.b Legal. This is just string concatenation.
1.c Legal. The variable bis just a reference, i.e. p ointer.
You can use it to point to whatever type you wish.
2. sys. excepthook (); half credit for
sys.excepthook()
3.
cmdlnargs = sys.argv[1:]
4. socket.connect();socket.accept()
5.
import os, sys
def checkthisdir(targetfile,dr,flst):
if targetfile in flst:
print os.path.join(dr,targetfile)
def findfile(dtroot,targetfile):
os.path.walk(dtroot,checkthisdir,targetfile)
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