Answer all four (4) questions.
You have 110 minutes to complete the exam.
This is an open-book exam. All written material is allowed.
No electronic devices other than a flash drive and the lab PC may be used during the exam.
No communication with others (electronic, verbal, written or otherwise) is allowed during the exam. Violations will result in a mark of zero and disciplinary action.
Add the Python code described below in the cells provided.
Test your code using the menu item Cell ► Run All
The message "Solution to question N may be correct." at the bottom of the notebook means that no errors were found in your answer to question N.
When the exam time is over, save the notebook (the .ipynb file) and upload it to the appropriate dropbox on the course web site.
Version 2 (fixed marking of Question 3)
Write a function named evens that takes a list argument named x. Your function should return a (new) list consisting of all the values of x which are even. For example, if x=[0, 3, 4, 2] your function should return [0, 4, 2].
def evens(x):
return [i for i in x if not i%2]
x=[0, 3, 4, 2]
evens(x)
Write a function named mergedicts that takes one list argument named l. The list l contains dictionaries. Your function should return one dictionary containing all key:value pairs in all dictionaries in l. For example if l = [{ 'a': 3, 'b': 9}, {1:2, "x":'y'}, {'sum':32}] then mergedicts(l) should return { 'a': 3, 'b': 9, 1:2, "x":'y', 'sum':32}. You may assume there are no duplicate keys.
def mergedicts(l):
return {k:d[k] for d in l for k in d}
l = [{ 'a': 3, 'b': 9}, {1:2, "x":'y'}, {'sum':32}]
mergedicts(l)
Write a recursive function named rcheck that takes a list argument named l and function argument f. Your function should call f with successive values of l until the return value is negative or all values of l have been tested. Your function does not return a value. For example if x=[1,2,3] and f(2) returns -1 then rcheck would call f(1) and f(2) and then return.
def rcheck(l,f):
if len(l) < 1 or f(l[0]) < 0:
return
else:
rcheck(l[1:],f)
def f(x):
print(x)
return -1 if x == 2 else 1
# alternative solution that modifies l
def rcheck(l,f):
if l and f(l[0]) >= 0:
l.pop(0)
rcheck(l,f)
l=[1,2,3]
rcheck(l,f)
print(l)
Set the variable pat to a regular expression that matches a part number string created according to the following sequence:
For example, re.search(pat,'CSTCE50M00G00C-R0') would return a match object but re.search(pat,'CSTCE50M0G00C-R00') would not.
pat=r'^CSTCE\d\d?M00?[GV]\d\dC?-R0$'
import re
print(re.search(pat,'CSTCE50M00G00C-R0'))
print(re.search(pat,'CSTCE50M0G00C-R00'))
# exam validation code; do not modify
def examcheck():
import copy, hashlib, re
from random import randint, choices, shuffle
def randwords(n):
l = set()
while len(l)<n:
l |= set((''.join([chr(randint(97,122)) for i in range(randint(2,5))]),))
return list(l)
def checksorted(l):
assert all((l[i] <= l[i+1] for i in range(len(l)-1))), \
"result is not sorted: {}".format(l)
def checkfunctions(f,l):
u=[s for s in f.__code__.co_names if s not in l]
assert not u, "You used the function(s): {}".format(u)
def checkrecursive(f):
s=f.__name__
assert s in f.__code__.co_names, "{} is not recursive".format(s)
def checkhash(l,n):
# print(hashlib.md5(''.join(l).encode('utf8')).hexdigest())
assert hashlib.md5(''.join(l).encode('utf8')).hexdigest() == n, \
'wrong values in list: {} ... {}'.format(l[0],l[-1])
def checkre(pat,ok,nok):
for s in ok:
assert re.search(pat,s), \
"pattern '{}' didn't match string '{}'".format(pat,s)
for s in nok:
assert not re.search(pat,s), \
"pattern '{}' matched string '{}'".format(pat,s)
def q1():
n=randint(2,5)
xe=choices(range(0,100,2),k=n)
xo=choices(range(1,100,2),k=n)
x=xe+xo
shuffle(x)
y=evens(x)
assert len(y) == len(xe) and all((i in xe for i in y)), \
"output is {} for input {}".format(y,x)
def q2():
ll=[randint(2,4) for i in range(randint(2,4))]
n=sum(ll)
r=randwords(n)+list(range(n))
shuffle(r)
l=[{r.pop():r.pop() for i in range(n)} for n in ll]
l0=copy.deepcopy(l)
y=mergedicts(l)
assert len(y) == n and all([k in y and y[k] == d[k] for d in l0 for k in d]), \
"mergedicts({}) returns {}".format(l0,y)
def q3():
checkrecursive(rcheck)
n=randint(3,5)
l=[randint(0,9) for i in range(n)]
fl=[]
def found(x):
fl.append(x)
return -1 if x == 2 else 1
l0=copy.copy(l)
rcheck(l,found)
m = l0.index(2)+1 if 2 in l0 else len(l0)
assert fl == l0[:m], "rcheck({}) called f with {}".format(l0,fl)
def q4():
ok=['CSTCE5M00G00C-R0', 'CSTCE50M0G00C-R0', 'CSTCE50M00V00C-R0',
'CSTCE50M00G45C-R0', 'CSTCE1M00G11-R0' ]
nok=[' CSTCE50M00G00C-R0', 'CSTCE123M00G00C-R0', 'CSTCE50m000G00C-R0',
'CSTCE50M0000C-R0', 'CSTCE50M00G00C-R' ]
checkre(pat,ok,nok)
for i,s in ((i,'q%d'%i) for i in range(1,20)):
if s in locals():
try:
locals()[s]()
print("Solution to question {} may be correct.".format(i))
except Exception as e:
print("Failed check for question {}: {}".format(i,e))
examcheck()