1. list of random numbers
using the following code, create a list of 25 random numbers
import random
random.randint(0, 100) # generates a random number between 0 and 100
example result: (write code to randomly create this list)
[90, 10, 14, 15, 20, 20, 87, 23,
8, 2, 44, 29, 10, 13, 33, 99,
9, 3, 23, 25]
import random
rand = []
for i in range(25):
rand.append(random.randint(0, 100))
print(rand)
2. create a sub-list
create a list of all the numbers between 0-100 that are dividible by 7:
0, 7, 14, 21, …
how many different ways can you think of to do this?
- using a for loop
- using range
- using range and slicing
# 1
a = []
for i in range(100):
if i%7==0:
a.append(i)
print(a)
#2
b = list(range(0, 100,7))
print(b)
#3
c = list(range(100))[::7]
print(c)
3. removing from a list *
remove from the list you created in question #1, all the numbers that are divisible by 7
how many ways can you think of doing this?
- using
.remove() - using
.pop()
test your solution using this code:
for x in mylist:
assert i % 7 != 0
number7s = list(range(0, 100,7))
# remove
list1 = sorted(rand[:]) # copy and sort list from #1
print("random list: ", list1)
print('all divisible by 7: ', number7s)
print()
number7s = list(range(0, 100, 7)) # multiples of 7
for x in number7s:
while x in list1:
list1.remove(x) #remove() removes only the first occurance
print(sorted(list1))
for x in list1:
assert x % 7 != 0
# pop solution #1
list2 = rand[:]
i=0
while i<len(list2):
if list2[i] in number7s:
list2.pop(i)
else:
i+=1
print(sorted(list2))
# pop solution #2
list3 = rand[:]
# iterate on the list in reverse to avoid changing indexes
for i in range(len(list3) - 1, -1, -1):
if list3[i] in number7s:
list3.pop(i)
print(sorted(list3))
4. reversing words in a sentence
print the words in the following sentence in reverse order
the quick brown fox jumped over the lazy dog
--> dog lazy the over jumped fox brown quick the
do it in as many ways as you can
- using slicing
- using pop
- using loop and range
x="the quick brown fox jumped over the lazy dog"
# slicing
print(" ".join(x.split()[::-1]))
# pop
words = x.split()
while words:
print(words.pop(), end=" ")
print()
# loop and range
words = x.split()
for i in range (-1, -len(words) -1, -1):
print(words[i], end=" ")
print()
# loop and slicing
for word in x.split()[::-1]:
print(word, end=" ")
print()
# reversed
print(" ".join(list(reversed(x.split()))))
# in place reverse
words = x.split()
words.reverse() # in-place
print(" ".join(words))
5. remove first and last
remove the first and last numbers from the list #1 and put them in variable x,y how can you do this with the least number of lines?
- using indexing and -1
- using unpacking
- using pop
print(rand)
# using indexing and -1
list1 = rand[:] # list from #1
x, y = list1[0], list1[-1]
print(x, list1[1:-1], y)
#using unpacking
list1 = rand[:] # list from #1
x, *everythingelse, y = list1
print(x, everythingelse, y)
# using pop
list1 = rand[:] # list from #1
x,y =list1.pop(0), list1.pop(-1)
print(x,list1, y)
6. intersection between lists
create any two lists list1, list2 example:
list1 = "the fox condemns the trap, not himself".split()
list2 = "the quick brown fox jumped over them lazy dog".split()
- now, using the keyword ‘in’ and a loop check if list1 has any item that also belongs in list2
- now also create a list called list_1_2 that has the entire list of items that exist in both list1 and list2
### useful: test data
list1 = "the fox condemns the trap, not himself".split()
list2 = "the quick brown fox jumped over the lazy dog".split()
# 1)
for word in list1:
if word in list2:
print('1:', word)
break
# 2)
words = []
for word in list1:
if word in list2:
words.append(word)
print('2:', words)
7. intersection between lists using sets
solve question #6 using set
hint: you no longer need loops
print( set(list1) & set(list2)) # & calls set.intersection
8. random numbers without duplicates
using the type set,
- create a list of exactly 20 random numbers(between 0-100),
- that have no duplicates
result=set()
while len(result) < 20:
result.add(random.randint(0, 100))
print(sorted(result))
9. remove duplicates
- create a list of 15 random numbers betwen 1-10
- using the type
set()
remove all the duplicate numbers from the list
- do it without caring about the order of items
**can you also do it, while preserving the original order of the list?
rand = []
for i in range(15):
rand.append(random.randint(0, 10))
list1 = rand[:]
print(list1)
# in normal sorted order
print(set(list1))
# in the same order as the original list
print(sorted(set(list1), key=list1.index))
10. uniques and dups **
- get a list of 20 random numbers, each in range 0-10
- from this list, which numbers were …
- unique? i.e. they appeared only once in the list?
- dups? i.e. they appeared more than once in the list?
hint: you may need a for loop and having one or two sets
# create random list
rand = []
for i in range(20):
rand.append(random.randint(0, 10))
# calculate uniques
seen = set()
uniq = set()
for x in rand:
if x not in seen:
uniq.add(x)
seen.add(x)
else:
uniq.discard(x)
# print results
dups = seen - uniq
print(sorted(rand))
print("seen: ", seen)
print("uniques: ", uniq)
print("dups: ", dups)
11. results of automated testing
imagine you’re running automated tests for a new build of your project. and this build “build1” fails some test. then the engineers go on to try to fix the bugs and create “build2” which also fails some tests
example:
build1_fails = [1, 3, 6, 12, 13, 19, 20, 23, 24, 25, 33, 34, 45, 66, 67, 87, 100, 145, 149]
build2_fails = [2, 9, 10, 11, 12, 13, 14, 15, 16, 19, 20, 87, 88, 89, 145, 146 ]
- which tests were fixed by build2? that is, they failed in build1 and stopped failing in build2?
- which tests got broken by build2? that is, they worked on build1 and started failing in build2?
- which broken tests did not get solved by build2? that is, they failed on both build1 and build2?
**which tests succeeded in both builds (hint: imagine there are 150 tests overall, named 1, 2, …, 149, 150)
### useful: example data
build1_fails = [1, 3, 6, 12, 13, 19, 20, 23, 24, 25, 33, 34, 45, 66, 67, 87, 100, 145, 149]
build2_fails = [2, 9, 10, 11, 12, 13, 14, 15, 16, 19, 20, 87, 88, 89, 145, 146 ]
print("1: ", set(build1_fails) - set(build2_fails))
print("2: ", set(build2_fails) - set(build1_fails))
print("3: ", set(build1_fails) & set(build2_fails))
print()
print("4: ", set(range(150)) - (set(build2_fails) | set(build1_fails) ))
12. 144 dictionary
- look at your phone’s phonebook, and select 4 people you have phone numbers for
- create an “144” dictionary for these people that maps names of people to their phone numbers
d144 = {
"avi" : "053-111",
"ben" : "053-222",
"hen" : "053-222",
"gaddy" : "053-333",
"daddy" : "053-333",
"zvi" : "053-444",
"zvika" : "053-444"
}
13. reverse 411 dictionary
-
take the dictionary from the previous question and create a reverse “411” dictionary that maps phone numbers back to people’s names
-
**sharing phone numbers:- what happens if two people share the same phone number?
- can you still reverse the dictionary and preserve all the information?
#1
d441 = {}
for name, phone in d144.items():
d441[phone] = name
print(d441)
#2
d441 = {}
for name, phone in d144.items():
if phone not in d441:
d441[phone] = [name]
else:
names = d441[phone]
names.append(name)
print(d441)