for Looppython3try Clauseelse Clausefor Loop with Listslen Functionin Operatordel Statementfor Loop with StringsThe final exam will be held on Thursday, May 16th from 11:30AM - 2:30PM.
The exam will be given in this room.
If for some reason you are not able to take the Final at the time it will be offered, you MUST send an email to me before the exam so we can make alternative arrangements.
The final will consist of questions like those on the quizzes, along with questions asking you to write short segments of Python code.
60% of the points on this exam will consist of questions from the Ungraded Class Quizzes.
You do not need to study a Class Quiz question if the topic is not mentioned in either the Midterm or Final review.
The remaining 40% will come from 4 questions that ask you to write some code.
To study for the code questions you should be able to
A good way to study for the code questions is to review the Class Exercises homework solutions and Class Notes.
Todays class will be a review session.
You will only be responsible for the material in today's class and the review for the Midterm, which you will find here.
Although the time alloted for the exam is 3 hours, I would expect that most of you would not need that much time.
The final is a closed book exam.
To prevent cheating, certain rules will be enforced during the exam.
Remember, the Midterm and Final determine 50% of your grade.
At the end of each semester we offer you the opportunity to say what you think about this course.
What have I done right?
What have I done wrong?
What can I do better?
You are not asked for you name.
So the submissions are anonymous.
I will not see your responses until after I have submitted grades for this course.
We collect this feedback through Course Evaluations.
I will use what you say to make this course better.
To complete the course evaluation, use the following link .
You have until Friday, May 24th, to submit the evaluation.
A normal semester has 28 classes.
But this semester has 29.
I do not have materials for a 29th class.
Next Tuesday I will have Zoom Office Hours, from 9 AM to 5 PM,instead of a class.
The Zoom session will be conducted from my home in Somerville.
Not my office on the UMB campus.
Are there any questions before I begin?
>>> result = round(8.765)
>>> result
9
return EXPRESSION
return statement does two things
return statement can return more than one value
return EXPRESION, EXPRESSION [, EXPRESSION, ...]
>>> def get_full_name():
... first_name = input("Please enter your first name: ")
... last_name = input("Please enter your last name: ")
... return first_name, last_name
...
>>> fname, lname = get_full_name() Please enter your first name: Glenn Please enter your last name: Hoffman
openopen function does two things
open function
FILE_VARIABLE = open(FILENAME, MODE)
| Mode | Description |
|---|---|
| "r" | Open a file for reading only |
| "w" | Open a file for writing |
| "a" | Open a file for writing to the end of the file |
for Loopfor
loop
for loop has this format
for LOOP_VARIABLE in LIST_OF_SOME_KIND:
for line in file:
print(line.strip())
python3python3 at the command line we are running
this binary file
python3 the filename of the
Python script
python3 then executes all the Python statements in the
file
# prints a friendly message
print("Hello world!")
$ python3 hello_1.py Hello world!
python3chmod command
chmod 755 FILENAME
#! /usr/bin/python3
>>> name = "Glenn"
>>> print(nme)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'nme' is not defined
average = num_1 + num_2 / 2
print ("Average:", average)
$ ./file_open.py
Filename: xxxxxx
Traceback (most recent call last):
File "./file_open.py", line 6, in <module>
file = open(filename, "r")
FileNotFoundError: [Errno 2] No such file or directory: 'xxxxxx'
try/except statement
which has the following form
try:
STATEMENT
STATEMENT
...
except:
STATEMENT
STATEMENT
...
try
code block
causes a runtime error ...
except code block and executes
those statements
open to create a file
try/except
statement
$ cat open_file.py
#! /usr/bin/python3
# demonstrates using a try/except statement
# to catch exceptions encountered while
# trying to open a file
filename = input("Filename: ")
try:
file = open(filename, "r")
for line in file:
print(line.rstrip())
except:
print("Could not open file", filename)
$ ./open_file.py
Filename: xxxx
Could not open file xxxx
for loopinput to ask the user for a numberinput returns a stringint and float can cause a runtime error ...try/except
statement
while loop
def get_integer():
while True:
number = input("Integer: ")
try:
number = int(number)
return number
except:
print(number, "cannot be converted into an integer")
try Clauseopen statement
in the try block of a try/except
statement
try/except
statement
filename = input("Filename: ")
try:
file = open(filename, "r")
except:
print("Cannot open", filename)
count = 0
total = 0
for line in file:
count += 1
date, temp = line.split()
temp = int(temp)
total += temp
average = round(total/count, 2)
print("Average:", average)
$ ./temps_average_3.py
Filename: xxx
Cannot open xxx
Traceback (most recent call last):
File "./temps_average_3.py", line 15, in <module>
for line in file:
NameError: name 'file' is not defined
open statement working try/exceptstatement else Clausetry/except statement can also have an
else clause
try block code does not cause a runtime errortry
clause to work ...
else clause
try:
file = open(filename, "r")
except:
print("Cannot open", filename)
else:
count = 0
total = 0
for line in file:
count += 1
date, temp = line.split()
temp = int(temp)
total += temp
average = round(total/count, 2)
print("Average:", average)
>>> even_numbers = [2, 4, 6, 8, 10] >>> even_numbers [2, 4, 6, 8, 10]]
>>> name = "Glenn" + " " + "Hoffman" >>> name 'Glenn Hoffman'
>>> n1 = [1,2,3] >>> n2 = [4,5,6] >>> n1 + n2 [1, 2, 3, 4, 5, 6]
>>> n1 / n2
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for /: 'list' and 'list'
>>> zeros = [0] * 5 >>> zeros [0, 0, 0, 0, 0] >>> numbers = [1, 2, 3] * 3 >>> numbers [1, 2, 3, 1, 2, 3, 1, 2, 3]
>>> "Go " * 3 'Go Go Go '
for Loop with Listsfor loop will work with a list
>>> numbers = [1, 2, 3, 4, 5] >>>for n in numbers: ... print(n) ... 1 2 3 4 5
for loop with strings
>>> team = "Red Sox" >>> for char in team: ... print(char) ... R e d S o x >>>
>>> even_numbers[0] 2 >>> even_numbers[1] 4 >>> even_numbers[2] 6
len Functionlen will return the length of any
sequence
>>> even_numbers = [2, 4, 6, 8, 10]
>>> len(even_numbers)
5
>>> len("foo")
len with range to iterate
through a list
for i in range(len(even_numbers)): ... print(even_numbers[i]) ... 2 4 6 8 10
numbers = [1, 4, 6, 8]
>>> numbers[0] = 2 >>> numbers [2, 4, 6, 8]
for loop to change every element
inside a list
>>> for i in range(len(numbers)): ... numbers[i] += 1 ... >>> numbers [3, 5, 7, 9]
>>> new_list = [] >>> new_list []
in Operatorin is an operator that works on objects
that are a collection of values
VALUE in LIST
in operator returns True if the
LIST contains VALUE
False
>>> digits [1, 2, 3, 4, 5, 6, 7, 8, 9, 0] >>> 1 in digits True >>> 11 in digits False
| Method | Description |
|---|---|
| append(item) | Adds item to the end of the list |
| sort() | Sorts the items in the list so they appear in ascending order (from the lowest value to the highest value) |
| reverse() | Reverses the order of the items in the list |
>>> teams = [] >>> teams []
>>> teams.append("Red Sox")
>>> teams
['Red Sox']
>>> teams.append("Orioles")
>>> teams.append("Blue Jays")
>>> teams.append("Rays")
>>> teams.append("Yankees")
>>> teams ['Red Sox', 'Orioles', 'Blue Jays', 'Rays', 'Yankees']
>>> l2 = [9, 1, 0, 2, 8, 6, 7, 4, 5, 3] >>> l2 [9, 1, 0, 2, 8, 6, 7, 4, 5, 3] >>>l2.sort() >>> l2 [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> l3 = [5, 4, 3, 2, 1] >>> l3.reverse() >>> l3 [1, 2, 3, 4, 5] >>> l3.reverse() >>> l3 [5, 4, 3, 2, 1]
>>> l4 = [2, 5, 9, 1, 8, 6, 3, 7, 4] >>> l4.sort() >>> l4 [1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> l4.reverse() >>> l4 [9, 8, 7, 6, 5, 4, 3, 2, 1]
del Statementdel
statement
del LIST_VARIABLE[INDEX]
del comes the list variable >>> l5 = [1, 2, 3, 4, 5, 6] >>> del l5[2] >>> l5 [1, 2, 4, 5, 6]
min returns the smallest value in a list
>>> l6 [1, 4, 5, 6] >>> min(l6) 1
max returns the largest
max(l6) 6
create an empty list
for each line in the file:
append the line to the empty list
file = open("numbs.txt", "r")
total = 0
numbers = []
for line in file:
num = int(line)
numbers.append(num)
total += num
>>> team = "Red Sox"
>>> team[0] 'R'
for Loop with Stringsfor loop
>>> for ch in team: ... print(ch) ... R e d S o x
>>> def character_count(string, char):
... count = 0
... for ch in string:
... if ch == char:
... count += 1
... return count
...
>>> character_count("Mississippi", "i")
4
>>> character_count("Mississippi", "s")
4
>>> character_count("Mississippi", "p")
2
for loop to reverse a string
>>> def string_reverse(string):
... new_string = "
... for ch in string:
... new_string = ch + new_string
... return new_string
...
>>> string_reverse("Mississippi")
'ippississiM'
>>> string_reverse("radar")
'radar'
>>> string_1 = "Red" >>> string_1 = string_1 + " Sox" >>> string_1 'Red Sox'
string_1 += " Sox"two things are happening
| Method | Description |
|---|---|
| lower | Returns a copy of the string with all alphabetic letters
converted to lowercase. Any character that is already lowercase, or is not an alphabetic letter, is unchanged. |
| upper | Returns a copy of the string with all alphabetic letters
converted to uppercase. Any character that is already uppercase, or is not an alphabetic letter, is unchanged. |
| strip | Returns a copy of the string with leading and trailing
characters removed. When run without an argument, it removes leading and tailing whitespace characters. When run with an argument, removes those characters. |
| split | Creates a list from a string. In order to do this it needs to know which character separates one value from another. This value is call a delimiter. The default value for the delimiter is whitespace |
>>> s = "foo bar bletch" >>> s.split() ['foo', 'bar', 'bletch']
>>> date = "2021-05006"
>>> date.split("-")
['2021', '05006']