class Book():

favs = [] #class

def __init__(self, title, pages):

self.title = title

self.pages = pages

def is_short(self):

if self.pages < 100:

return true

#What happens when you pass object to print?

def __str__(self):

return f"{self.title}, {self.pages} pages long"

#What happens when you use ==?

def __eq__(self, other):

if(self.title == other.title and self.pages == other.pages):

return True

#It's approriate to give something for __hash__ when you override __eq__

# #This is the recommended way if mutable (like it is here):

__hash__ = None

########## Passing by Object Reference ##########

book = Book("Where Is My Mother?", 100)

print(book)

def modify(book):

book.title = "Changed noob"

modify(book)

print(book)

#What is we print id to follow?

def modify(book):

print(id(book))

book.title = "Changed noob"

print(id(book))

print(id(book))

modify(book)

print(id(book))

#We get the same number for everything

book = Book("Are You My Mother?", 100)

print("let's reassign")

def modify(book):

print(id(book))

book = Book("Changed noob", 100)

print(id(book)) #This is a different id.

#The original is unchanged. Reassigning

print(id(book))

modify(book)

print(id(book))

print(book) #Stayed the same!

########## Reading from a file ##########

file = open("input.txt", "a") #append. Creates if not there

file = open("input.txt", "w") #overwrites

#file = open("input.txt", "r+") #Read and write. Throws exception if not there

#not as easy to work with on r/w in my oppinion

#\t to sep title from page count

file.write("Are You My Mother?\t72\n")

file.write("The Digging-est Dog\t72")

file.close() #close when done

file = open("input.txt", "r")

#for line in file:

# print(line, end="") #end="" as \n is kept in line

#print()

#Numerous ways to read into list. Here is one.

data = file.read().split('\n')

print(data)

#https://stackoverflow.com/questions/3277503/how-to-read-a-file-line-by-line-into-a-list

file.close()

#Each line is title\tpages so we split it.

book1_data = data[0].split('\t')

book = Book(book1_data[0], book1_data[1])

book2_data = data[1].split('\t')

book2 = Book(book2_data[0], book2_data[1])

print(book)

print(book2)

########## Intro to Exception handling ##########

#When working with files (or doing anything in programming),

#Exceptions can be thrown

#file = open("doesntexist.csv", "r") #get wrecked son

try:

file = open("doesntexist.csv", "r")

except Exception as e:

print(type(e))

print(e)

try:

file = open("input.txt", "r") #Make sure it exists

data = int(file.read()) #This should fail

except FileNotFoundError as e: #subclass of OSError

print("This file is not found")

except OSError as e:

print("Couldn't open file")

except PermissionError as e:

print("file is locked")

except ValueError as e:

print("Cannot parse data. Check file")

except Exception as e:

print(type(e))

print(e)

finally:

file.close()

print("Always runs")

########## with keyword ##########

#shorthand for opening file and automatically closed outside indent

with open("input.txt", "r") as file: #Make sure it exists

try:

int(file.read())

except: #example of using thin except here

print("parse error...etc...")

#do whatever

print(file.closed) #closed

#opening can still throw an exception...Maybe do it like so:

try:

with open("no", "r") as file:

int(file.read())

except Exception as e:

print(e)

#I think this could be written like so but may require another try inside else:

try:

file = open('nope')

except OSError as e:

print(e)

else:

with file:

#try:

file.read()

#except Exception as e:

# print(e)

#https://stackoverflow.com/questions/40640956/python-with-open-except-filenotfounderror/40641103

#https://stackoverflow.com/questions/28633555/how-to-handle-filenotfounderror-when-try-except-ioerror-does-not-catch-it