class Base(object):
    pass

class Derived(Base):
    pass

class Bag(object):
    
    def __init__(self):
        self.contents = list()
    
    def put(self, obj):
        self.contents.append(obj)
        
    def __str__(self):
        res ="A bag containing:\n"
        for item in list(self.contents):
            res += "- " + item + "\n"
        return res
        
my_bag = Bag()
my_bag.put("phone")
my_bag.put("keys")
my_bag.put("banana")

print(my_bag)

A bag containing:
- phone
- keys
- banana

class Bag(object):
    
    def __init__(self):
        self.contents = list()
    
    def put(self, obj):
        self.contents.append(obj)

    def __str__(self):
        return "Bag contents: " + str(self.contents)
        
my_bag = Bag()
my_bag.put("phone")
my_bag.put("keys")
my_bag.put("banana")

print(my_bag)

Bag contents: ['phone', 'keys', 'banana']

# Exempel 1
number = 5
name = "Ada"
print(number + name)

---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
Cell In[71], line 4
      2 number = 5
      3 name = "Ada"
----> 4 print(number + name)

TypeError: unsupported operand type(s) for +: 'int' and 'str'

# Exempel 2
ans = 5 / (42 * 0)

---------------------------------------------------------------------------
ZeroDivisionError                         Traceback (most recent call last)
Cell In[72], line 2
      1 # Exempel 2
----> 2 ans = 5 / (42 * 0)

ZeroDivisionError: division by zero

# Exempel 3
printt("Hello world")

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
Cell In[73], line 2
      1 # Exempel 3
----> 2 printt("Hello world")

NameError: name 'printt' is not defined

# krasch.py
# Exempel på kod som kraschar
letters = ["a", "b", "c", "d", "e", "f"]

index = 0
while True:
    print(f"letters[index]: {letters[index]}")
    index += 1
print("Program done.")

letters[index]: a
letters[index]: b
letters[index]: c
letters[index]: d
letters[index]: e
letters[index]: f

---------------------------------------------------------------------------
IndexError                                Traceback (most recent call last)
Cell In[74], line 7
      5 index = 0
      6 while True:
----> 7     print(f"letters[index]: {letters[index]}")
      8     index += 1
      9 print("Program done.")

IndexError: list index out of range

# undantag1.py
# Undantag hanterat, kraschar inte
letters = ["a", "b", "c", "d", "e", "f"]

try:
    index = 0
    while True:
        print("letters[index]: {}".format(letters[index]))
        index += 1
    print("Loop done.")
except:
    print("An exception was raised.")
print("Program done.")

letters[index]: a
letters[index]: b
letters[index]: c
letters[index]: d
letters[index]: e
letters[index]: f
An exception was raised.
Program done.

# undantag2.py
letters = ["a", "b", "c", "d", "e", "f"]
try:
    index = 0
    while True:
        print(letters[index])
        index += 1
# Om undantag inträffar kommer variabeln error referera till en
# instans av klassen Exception
except Exception as error:
    print("An exception was raised.")
    print(error)
print("Program done.")

a
b
c
d
e
f
An exception was raised.
list index out of range
Program done.

# undantag3.py
import random

def run_until_exception():
    values = ["a", 2, "c", 4, "e", "f"]
    try:
        while True:
            # slumpa fram två index som ev. kan vara ogiltiga
            index1 = random.randint(0, len(values))
            index2 = random.randint(0, len(values))
            # använd operatorn +. Fel om operanderna inte är samma datatyp.
            print(f"{values[index1]} + {values[index2]} -> {values[index1] + values[index2]}")
    except TypeError as exception:
        print(f"TypeError: {exception}. Tried {values[index1]} + {values[index2]}")
    except IndexError as exception:
        print(f"IndexError: {exception}, {len(values)=}, {index1=}, {index2=}")

run_until_exception()
print("Program done.")

c + f -> cf
4 + 2 -> 6
2 + 4 -> 6
TypeError: can only concatenate str (not "int") to str. Tried c + 4
Program done.

class City(object):
    
    def __init__(self, name):
        self.households = []
        self.name = name
        
    def add_household(self, household):
        self.households.append(household)
        
    def get_population(self):
        total_population = 0
        for household in self.households:
            total_population += household.get_num_members()
        return total_population
    
    def __str__(self):
        output = f"City: {self.name}\nPopulation: {self.get_population()}\n"
        for household in self.households:
            output += f" * {household}\n"
        return output

class Household(object):
    
    def __init__(self, name):
        self.name = name
        self.members = []
        
    def add_member(self, name):
        self.members.append(name)
        
    def get_num_members(self):
        return len(self.members)    
    def __str__(self):
        return f"Household '{self.name}', ({self.get_num_members()} ppl)"

flaxtown = City("Linköping")

household1 = Household("Rydsvägen 1")
household1.add_member("A")
household1.add_member("B")

household2 = Household("Rydsvägen 2")
household2.add_member("C")

flaxtown.add_household(household1)
flaxtown.add_household(household2)

print(flaxtown)

City: Linköping
Population: 3
 * Household 'Rydsvägen 1', (2 ppl)
 * Household 'Rydsvägen 2', (1 ppl)

from bank3 import *


def new_client(bank):
    print("new_client() körs")


def show_clients(bank):
    print("show_clients() körs")


def main():
    bank = Bank()
    while True:
        user_input = input("Vad vill du göra? ").lower()
        if user_input == 'q':
            break
        elif user_input == "ny kund":
            new_client(bank)
        elif user_input == "visa kunder":
            show_clients(bank)
        else:
            print("Okänt kommando.")


if __name__ == '__main__':
    main()

from bank3 import *


def new_client(bank):
    print("new_client() körs")


def show_clients(bank):
    print("show_clients() körs")


def main():
    commands = {'ny kund': new_client,
                'visa kunder': show_clients}
    bank = Bank()

    while True:
        user_input = input("Vad vill du göra? ").lower()
        if user_input == 'q':
            break
        elif user_input in commands:
            commands[user_input](bank)
        else:
            print("Okänt kommando.")


if __name__ == '__main__':
    main()

from bank3 import *


def new_client(bank):
    print("new_client() körs")


def show_clients(bank):
    print("show_clients() körs")


def main():
    commands = {'ny kund': new_client,
                'visa kunder': show_clients}
    bank = Bank()

    while True:
        user_input = input("Vad vill du göra? ").lower()
        try:
            if user_input == 'q':
                break
            commands[user_input](bank)
        except KeyError:
            print("Okänt kommando.")


if __name__ == '__main__':
    main()

from bank3 import *


def new_client(bank):
    while True:
        confirmed = ""
        client_name = input("Ange kundens namn: ")
        while confirmed not in ["j", "n"]:
            confirmed = input(f"Du skrev '{client_name}', är det OK? [j/n]: ")
        if confirmed == "j":
            bank.new_client(client_name)
            break
        else:
            print("Ok, skriv in igen!")


def show_clients(bank):
    print(bank)


def main():
    commands = {'ny kund': new_client,
                'visa kunder': show_clients}
    bank = Bank()

    while True:
        user_input = input("Vad vill du göra? ").lower()
        try:
            if user_input == 'q':
                break
            commands[user_input](bank)
        except KeyError:
            print("Okänt kommando.")

main()

from bank3 import *

def get_user_confirmation(message, yes, no):
    user_input = ""
    while user_input not in [yes, no]:
        user_input = input(f"{message} [{yes}/{no}]: ")
    return user_input == yes


def new_client(bank):
    while True:
        client_name = input("Ange kundens namn: ")
        message = f"Du skrev '{client_name}', är det OK?"
        if get_user_confirmation(message, "j", "n"):
            bank.new_client(client_name)
            break
        else:
            print("Ok, skriv in igen!")


def show_clients(bank):
    print(bank)


def main():
    commands = {'ny kund': new_client,
                'visa kunder': show_clients}
    bank = Bank()

    while True:
        user_input = input("Vad vill du göra? ").lower()
        try:
            if user_input == 'q':
                break
            commands[user_input](bank)
        except KeyError:
            print("Okänt kommando.")


if __name__ == '__main__':
    main()

from bank3 import *

class BankApp(object):

    def __init__(self):
        self.commands = {'ny kund': self.new_client,
                         'visa kunder': self.show_clients}
        self.bank = Bank()

    def run(self):
        while True:
            user_input = input("Vad vill du göra? ").lower()
            try:
                if user_input == 'q':
                    break
                self.commands[user_input]()
            except KeyError:
                print("Okänt kommando.")

    def get_user_confirmation(self, message, yes, no):
        user_input = ""
        while user_input not in [yes, no]:
            user_input = input(f"{message} [{yes}/{no}]: ")
        return user_input == yes

    def new_client(self):
        while True:
            client_name = input("Ange kundens namn: ")
            message = f"Du skrev '{client_name}', är det OK?"
            if self.get_user_confirmation(message, "j", "n"):
                self.bank.new_client(client_name)
                break
            else:
                print("Ok, skriv in igen!")

    def show_clients(self):
        print(self.bank)


if __name__ == '__main__':
    app = BankApp()
    app.run()

729G46 Informationsteknologi och programmering¶

Tema 6, Föreläsning 6.1-6.2¶

Johan Falkenjack, johan.falkenjack@liu.se¶