Question

class Tasks(object):
    def __init__(self, container=None):
        if container is None:
            container = []
        self.container = container


    def add(self,name,date,priority):
        self.container.append([name,date,priority])

    def __str__(self):
        return str(self.container)

    def __repr__(self):
        return str(self.container)

    def __getitem__(self, key):
        return Tasks(self.container[key])

    def __len__(self):
        return len(self.container)


class management(Tasks):
    def save(self):
        outfile = open ("tasks.txt","w")
        outfile.write(("\n".join(map(lambda x: str(x), task))))

        print task
        outfile.close ()
    def load(self):
        load_file = open("tasks.txt","r")
        task = load_file.readlines()
        print task
        #this line is the attempt to convert back into the original format
        Tasks(add(task))




task = Tasks()        
if __name__== "__main__":

    p = management(Tasks)

    #task.add("birthday","27092012","high")
    #task.add("christmas","20062000","medium")
    #task.add("easter","26011992","low")
    print task

    #print len(task)
    #p.save()
    p.load()


    print "test",task
    print len(task)

the ultimate aim of my code is to generate a task manager(to do list)

the code above generates a list of [name,date,priority], it then saves it in a text file called tasks.txt – as far as im aware this works perfectly(as long as i comment out p.load).

however… the load function loads the file but I need to be able to print the list it loads as print task as I did when I had commented out p.load().

this will enable me to be able to eventually, delete,sort etc. tasks

thanks in advance

I apologise for the bad question I didn’t know how to word it on1 line

edit:
I thought about pickling which would preserve the list format, but i dont think it would solve my problem of being able to pass the arguments back into the Tasks() class in order to be able to print them as print task

edit 2
the load function now reads

 def load(self):
     with open("tasks.txt", "r") as load_file:
         tasks = [ast.literal_eval(ln) for ln in load_file]
     print tasks
     for t in tasks:
         todo.add(t)

obviously (or at least I think ) I get the error NameError: global name ‘todo’ is not defined
I have tried with task.add(t) and get TypeError: add() takes exactly 4 arguments (2 given)

I also tried with Tasks.add(t) and got the error TypeError: unbound method add() must be called with Tasks instance as first argument (got list instance instead)

I clearly dont understand the code, could you clarify, thanks.

edit 3
while True:
menu_choice = int(input(“Select a number from the menu”))

try:
    if menu_choice == 1:

        task = raw_input ("task")
        date = raw_input ("date")
        priority = raw_input ("priority")
        tasks = Tasks([(task,date,priority)])
        print tasks


    elif menu_choice == 2:
        print tasks
    elif menu_choice == 3:
        tasks.save()
    elif menu_choice == 4:
        tasks.load()
except:
    print sys.exc_info()

this over writes the task each time instead of appending it, any ideas? also menu choice 2,3,4 dont work because tasks isnt defined globally, not sure how I can get round this? maybe returning?

Answer 1

Trying a different, more Pythonic approach. Not so much an answer, but more an alternative. Edited thrice to take into account a number of requests for new features.

import pickle

class TasksError(Exception):
    def __init__(self, value):
        self.value = value
    def __str__(self):
        return repr(self.value)

class Task(object):
    def __init__(self, task = () ):
        if task ==():
            raise TasksError('Empty task.')
        self.name = task[0]
        self.date = task[1]
        self.priority = task[2]

    def __str__(self):
        output = '''Name: %s
Date: %s
Priority: %s
''' % ( self.name,
        self.date,
        self.priority )
        return output

class Tasks(object):
    def __init__(self, container = []):
        self.container = [ Task(todo) for todo in container ]

    def find_by_priority(self, priority = 'high'):
        # example method to seek and print high priority tasks
        # using this example, you will be able to conduct many
        # types of searches
        results = [ task
                   for task in self.container
                   if task.priority == priority ]
        return results

    def sort_by_date(self):
        # example method of how to sort, again, many other
        # ways of sorting can be implemented, this is just
        # to demonstrate the principle
        # for more info on sorting,
        # visit:  http://wiki.python.org/moin/HowTo/Sorting
        self.container = sorted(self.container,
                                key=lambda task: task.date)

    def add(self, task):
        if task == '':
            raise TasksError('Empty task')
        self.container.append( Task(task) )

    def save(self):
        try:
            output = open('tasks.pkl', 'wb')
            pickle.dump(self.container, output)
            output.close()
        except:
            raise TasksError('Failed to save.')

    def load(self):
        try:
            pkl_file = open('tasks.pkl', 'rb')
            self.container = pickle.load(pkl_file)
            pkl_file.close()
        except:
            raise TasksError('Failed to load')

    def __str__(self):
        output = '\n'.join( [ str(todo) for todo in self.container ] )
        return output

if __name__== "__main__":
    divider = '-' * 30 + '\n'

    tasks = Tasks( [("birthday","20121111","high"),
                    ("christmas","20121225","medium"),
                    ("easter","20120405","low")] )
    print 'Three original tasks:\n'
    print tasks # prints out three tasks
    print divider

    tasks.add( ("new-task","20120320","high") )
    print 'Three original plus one new task:\n'
    print tasks # prints out four tasks
    print divider

    tasks.save() # pickles the task list and saves to disk

    tasks = Tasks( container = [] ) # creates a new, empty task list
    print 'Empty task list:\n'
    print tasks # prints out empty list
    print divider

    tasks.load() # loads the pickled list
    print 'The four pickled tasks, reloaded:\n'
    print tasks # prints out four tasks
    print divider

    while True:
        print divider, '''Make your selection:
1. Add new task
2. Print all tasks
3. Save tasks
4. Load tasks from disk
5. Find high priority tasks
6. Sort by date
<ENTER> to quit
'''
        try:
            menu_choice = int(input("Select a number from the menu: "))
        except:
            print 'Goodbye!'
            break

        if menu_choice == 1:
            # note: no error checking here
            # even an empty input is accepted
            task = raw_input (">>> Task: ")
            date = raw_input (">>> Date as string YYYYMMDD: ")
            priority = raw_input (">>> Priority: ")
            todo = (task, date, priority)
            # note that here you should add a task
            # your method created a NEW task list
            # and replaced the old one
            tasks.add( todo )
            print tasks
        elif menu_choice == 2:
            print divider, 'Printing all tasks'
            print tasks
        elif menu_choice == 3:
            print divider, 'Saving all tasks'
            tasks.save()
        elif menu_choice == 4:
            print divider, 'Loading tasks from disk'
            tasks.load()
        elif menu_choice == 5:
            print divider, 'Finding tasks by priority'
            results = tasks.find_by_priority(priority='high')
            for result in results: print result
        elif menu_choice == 6:
            print divider, 'Sorting by date'
            tasks.sort_by_date()
            print tasks

IMPORTANT NOTE: This is code produced as an exercise to demonstrate many of the features that you are seeking to implement and to show how a proper use of object oriented design allows you to encapsulate each task and task-list and to manipulate them with ease. It also demonstrates the use of pickle as a Pythonic alternative to the text file implementation that you were using in the original question. It also demonstrates searching and sorting by field, implementing two simple methods.

If you are serious about this project, you need to look at a proper database such as SQLite that will allow man more features for searching, sorting, updating, adding, and deleting records than you could reliably implement by hand.