outlines MVC

learning_python3.md

@@ -2744,6 +2744,576 @@ if __name__ == "__main__":
 
 ## MVC design pattern
 
+A simple console only MVC.
+We'll add the GUI view in a bit.
+
+```python
+import wx
+
+
+class ConsoleView(object):
+    """A view for console."""
+
+    def select_task(self):
+        """Asks which index to look up."""
+        idx = input("which task do you want to see? ")
+        return idx
+
+    def show(self, task):
+        """Displays the task to the console. This method is called from the
+        controller."""
+        print("your task: {}".format(task))
+
+    def error(self, msg):
+        """Prints error messages coming from the controller."""
+        print("error: {}".format(msg))
+
+
+class WxView(wx.Dialog):
+    pass
+
+
+class Model(object):
+    """The model houses add data and should implement all methods related to
+    adding, modifying and deleting tasks."""
+
+    db = ["go to the shops", "dryhop beer", "drop of motorbike"]
+
+    def get_task(self, idx):
+        """Performs a task lookun into the database and returns it when found.
+        If no task is found, it returns an error message that will be displayed
+        in the view (via the controller)."""
+        try:
+            task = Model.db[idx]
+        except IndexError:
+            task = "task with {} not found!".format(idx)
+        return task
+
+
+class Controller(object):
+    """Binds the model and the view together."""
+
+    def __init__(self, view):
+        self.model = Model()
+        self.view = view 
+
+    def run(self):
+        """The controller's main function. Depending on what type of view is 
+        selected, a different event loop is setup. Do note that the ConsoleView
+        is not a real event loop, just a basic flow of action."""
+        if self.view is ConsoleView:
+            self.view = self.view()
+            self._run_console_view()
+        elif self.view is WxView:
+            app = wx.App()
+            self.view = self.view()
+            self.view._set_controller(self)
+            app.MainLoop()
+
+    def get_task_from_model(self, idx):
+        """Needed for the WxView to communicate with the controller."""
+        task = self.model.get_task(idx)
+        self.view.show_task(task)
+
+    def _run_console_view(self):
+        """Super simple event loop."""
+        while True:
+            try:
+                idx = self.view.select_task()
+                idx = int(idx)
+            except Exception as e:
+                self.view.error(e)
+                continue
+            task = self.model.get_task(idx)
+            self.view.show(task)
+
+
+if __name__ == "__main__":
+    view = ConsoleView
+    # view = WxView
+    app = Controller(view)
+    app.run()
+```
+
+And now with the implemented `WxView` class.
+
+```python
+import wx
+
+
+class ConsoleView(object):
+    """A view for console."""
+
+    def select_task(self):
+        """Asks which index to look up."""
+        idx = input("which task do you want to see? ")
+        return idx
+
+    def show(self, task):
+        """Displays the task to the console. This method is called from the
+        controller."""
+        print("your task: {}".format(task))
+
+    def error(self, msg):
+        """Prints error messages coming from the controller."""
+        print("error: {}".format(msg))
+
+
+class WxView(wx.Dialog):
+    """A view using a wx.Dialog window"""
+
+    def __init__(self):
+        wx.Dialog.__init__(self, None, title="Task Manager")
+        self.panel = wx.Panel(self)
+        self.box = wx.BoxSizer(wx.VERTICAL)
+        self.task = wx.StaticText(self.panel, label="your task")
+        self.idx = wx.SpinCtrl(self.panel)
+        self.button = wx.Button(self.panel, label="submit")
+        self.button.Bind(wx.EVT_BUTTON, self.select_task)
+        self.box.Add(self.task, 0, wx.EXPAND, 1)
+        self.box.Add(self.idx, 0, wx.EXPAND, 1)
+        self.box.Add(self.button, 0, wx.EXPAND, 1)
+        self.panel.SetSizer(self.box)
+        self.Show()
+
+    def _set_controller(self, controller):
+        """Set the controller so the view can communicate it's requests to it
+        and update it's values too."""
+        self.controller = controller
+
+    def select_task(self, event):
+        """Gets the index to look up in the model and submits the request to
+        the controller."""
+        idx = self.idx.GetValue()
+        self.controller.get_task_from_model(idx)
+
+    def show_task(self, task):
+        """Updates the visual label in the view with the task. This method is
+        called from the controller."""
+        self.task.SetLabel(task)
+
+
+class Model(object):
+    """The model houses add data and should implement all methods related to
+    adding, modifying and deleting tasks."""
+
+    db = ["go to the shops", "dryhop beer", "drop of motorbike"]
+
+    def get_task(self, idx):
+        """Performs a task lookun into the database and returns it when found.
+        If no task is found, it returns an error message that will be displayed
+        in the view (via the controller)."""
+        try:
+            task = Model.db[idx]
+        except IndexError:
+            task = "task with {} not found!".format(idx)
+        return task
+
+
+class Controller(object):
+    """Binds the model and the view together."""
+
+    def __init__(self, view):
+        self.model = Model()
+        self.view = view 
+
+    def run(self):
+        """The controller's main function. Depending on what type of view is 
+        selected, a different event loop is setup. Do note that the ConsoleView
+        is not a real event loop, just a basic flow of action."""
+        if self.view is ConsoleView:
+            self.view = self.view()
+            self._run_console_view()
+        elif self.view is WxView:
+            app = wx.App()
+            self.view = self.view()
+            self.view._set_controller(self)
+            app.MainLoop()
+
+    def get_task_from_model(self, idx):
+        """Needed for the WxView to communicate with the controller."""
+        task = self.model.get_task(idx)
+        self.view.show_task(task)
+
+    def _run_console_view(self):
+        """Super simple event loop."""
+        while True:
+            try:
+                idx = self.view.select_task()
+                idx = int(idx)
+            except Exception as e:
+                self.view.error(e)
+                continue
+            task = self.model.get_task(idx)
+            self.view.show(task)
+
+
+if __name__ == "__main__":
+    view = WxView
+    app = Controller(view)
+    app.run()
+```
+
+For a GUI only login generator an implementation without MVC could look a bit like this.
+Note that the actual calculation is done inside the window itself.
+This is not a good idea because we should separate responsibilities into classes!
+
+```python
+import wx
+import login_generator
+
+
+class MainWindow(wx.Dialog):
+    def __init__(self):
+        wx.Dialog.__init__(self, None, title="Login Generator")
+        self.full_window = wx.Panel(self)
+        self.full_window_sizer = wx.BoxSizer(wx.VERTICAL)
+        self.full_window_sizer.Add(self.create_top_panel(), 0, wx.EXPAND | wx.ALL, 20)
+        self.full_window_sizer.Add(self.create_bottom_panel(), 0, wx.EXPAND, 0)
+        self.full_window.SetSizer(self.full_window_sizer)
+        self.Show()
+
+    def create_bottom_panel(self):
+        bottom_panel = wx.Panel(self.full_window)
+        bottom_panel_sizer = wx.BoxSizer(wx.HORIZONTAL)
+        self.login_list = wx.ListCtrl(bottom_panel, style=wx.LC_REPORT)
+        self.login_list.Bind(wx.EVT_RIGHT_UP, self.show_popup)
+        self.login_list.InsertColumn(0, 'username', width=200)
+        self.login_list.InsertColumn(1, 'password', width=200)
+        bottom_panel_sizer.Add(self.login_list, 0, wx.EXPAND | wx.ALL, 200)
+        return bottom_panel
+
+    def create_top_panel(self):
+        top_panel = wx.Panel(self.full_window)
+        top_panel_sizer = wx.BoxSizer(wx.HORIZONTAL)
+        self.login_amount = wx.TextCtrl(top_panel)
+        self.login_complex = wx.CheckBox(top_panel, label="complex")
+        self.login_create = wx.Button(top_panel, label="Create")
+        self.login_create.Bind(wx.EVT_BUTTON, self.add_login)
+        top_panel_sizer.Add(self.login_amount, 1, wx.EXPAND|wx.ALL,0)
+        top_panel_sizer.Add(self.login_complex, 1, wx.EXPAND|wx.ALL,0)
+        top_panel_sizer.Add(self.login_create, 1, wx.EXPAND|wx.ALL,0)
+        top_panel.SetSizer(top_panel_sizer)
+        return top_panel
+    
+    def show_popup(self, event):
+        menu = wx.Menu()
+        menu.Append(1, "Copy selected items")
+        menu.Bind(wx.EVT_MENU, self.copy_items, id=1)
+        self.PopupMenu(menu)
+
+    def copy_items(self, event):
+        selected_items = []
+        for i in range(self.login_list.GetItemCount()):
+            if self.login_list.IsSelected(i):
+                username = selected_items.append(
+                        self.login_list.GetItem(i, 0).GetText()
+                        )
+                password = selected_items.append(
+                        self.login_list.GetItem(i, 1).GetText()
+                        )
+        clipdata = wx.TextDataObject()
+        clipdata.SetText("\n".join(selected_items))
+        wx.TheClipboard.Open()
+        wx.TheClipboard.SetData(clipdata)
+        wx.TheClipboard.Close()
+
+    def add_login(self, event):
+        amount = self.login_amount.GetValue()
+        complex = self.login_complex.GetValue()
+        try:
+            amount = int(amount)
+        except:
+            amount = 1
+        for i in range(0, amount):
+            username = login_generator.generate_username()
+            password = login_generator.generate_password(12, complex)
+            index = self.login_list.InsertItem(0, username)
+            self.login_list.SetItem(index, 1, password)
+
+
+if __name__ == "__main__":
+    app = wx.App()
+    win = MainWindow()
+    app.MainLoop()
+```
+
+Now let's assume the generate username and password function take some calculation time.
+We'll add in a fake `time.sleep` to simulate.
+
+```python
+import wx
+import login_generator
+import time
+
+
+class MainWindow(wx.Dialog):
+    def __init__(self):
+        wx.Dialog.__init__(self, None, title="Login Generator")
+        self.full_window = wx.Panel(self)
+        self.full_window_sizer = wx.BoxSizer(wx.VERTICAL)
+        self.full_window_sizer.Add(self.create_top_panel(), 0, wx.EXPAND | wx.ALL, 20)
+        self.full_window_sizer.Add(self.create_bottom_panel(), 0, wx.EXPAND, 0)
+        self.full_window.SetSizer(self.full_window_sizer)
+        self.Show()
+
+    def create_bottom_panel(self):
+        bottom_panel = wx.Panel(self.full_window)
+        bottom_panel_sizer = wx.BoxSizer(wx.HORIZONTAL)
+        self.login_list = wx.ListCtrl(bottom_panel, style=wx.LC_REPORT)
+        self.login_list.Bind(wx.EVT_RIGHT_UP, self.show_popup)
+        self.login_list.InsertColumn(0, 'username', width=200)
+        self.login_list.InsertColumn(1, 'password', width=200)
+        bottom_panel_sizer.Add(self.login_list, 0, wx.EXPAND | wx.ALL, 200)
+        return bottom_panel
+
+    def create_top_panel(self):
+        top_panel = wx.Panel(self.full_window)
+        top_panel_sizer = wx.BoxSizer(wx.HORIZONTAL)
+        self.login_amount = wx.TextCtrl(top_panel)
+        self.login_complex = wx.CheckBox(top_panel, label="complex")
+        self.login_create = wx.Button(top_panel, label="Create")
+        self.login_create.Bind(wx.EVT_BUTTON, self.add_login)
+        top_panel_sizer.Add(self.login_amount, 1, wx.EXPAND|wx.ALL,0)
+        top_panel_sizer.Add(self.login_complex, 1, wx.EXPAND|wx.ALL,0)
+        top_panel_sizer.Add(self.login_create, 1, wx.EXPAND|wx.ALL,0)
+        top_panel.SetSizer(top_panel_sizer)
+        return top_panel
+    
+    def show_popup(self, event):
+        menu = wx.Menu()
+        menu.Append(1, "Copy selected items")
+        menu.Bind(wx.EVT_MENU, self.copy_items, id=1)
+        self.PopupMenu(menu)
+
+    def copy_items(self, event):
+        selected_items = []
+        for i in range(self.login_list.GetItemCount()):
+            if self.login_list.IsSelected(i):
+                username = selected_items.append(
+                        self.login_list.GetItem(i, 0).GetText()
+                        )
+                password = selected_items.append(
+                        self.login_list.GetItem(i, 1).GetText()
+                        )
+        clipdata = wx.TextDataObject()
+        clipdata.SetText("\n".join(selected_items))
+        wx.TheClipboard.Open()
+        wx.TheClipboard.SetData(clipdata)
+        wx.TheClipboard.Close()
+
+    def add_login(self, event):
+        amount = self.login_amount.GetValue()
+        complex_bool = self.login_complex.GetValue()
+        try:
+            amount = int(amount)
+        except:
+            amount = 1
+        for i in range(0, amount):
+            username = login_generator.generate_username()
+            password = login_generator.generate_password(12, complex_bool)
+            time.sleep(1)
+            index = self.login_list.InsertItem(0, username)
+            self.login_list.SetItem(index, 1, password)
+
+
+if __name__ == "__main__":
+    app = wx.App()
+    win = MainWindow()
+    app.MainLoop()
+```
+
+A clear separation of responsabilities can be acchieved via an MVC pattern and a login *library*.
+The library code is quite straightforward and goes as follows.
+It's basically the same code we did before but with added `try except` blocks.
+Can you tell me why I added those?
+
+```python
+import random
+import string
+
+
+def load_file(filename):
+    """
+    We load a file and make a list out of it. Note that the same function is 
+    used for both files (both adjectives and subjects). Functions should be 
+    made as generic as possible.
+
+    There IS a problem you can fix, some logins will have spaces in them. Try
+    to remove them in this function!
+    """
+    words = []
+    with open(filename, "r") as fp:
+        lines = fp.readlines()
+        for line in lines:
+            words.append(line.strip())          # what does strip() do, what does append() do? remember CTRL+Q!
+    return words
+
+
+def generate_username():
+    """
+    We'll generate a random pair of adjectives and subjects from two wordlists.
+    You NEED to have both files in you python project for this to work! Note 
+    the capitalize method call to make it all prettier...
+    """
+    try:
+        adjectives = load_file("./adjectives.txt")
+    except:
+        adjectives = ["big", "funny", "normal", "red"]
+    try:
+        subjects = load_file("./subjects.txt")
+    except:
+        subjects = ["giraffe", "elephant", "cougar", "tiger"]
+    adjective = random.choice(adjectives)
+    subject = random.choice(subjects)
+    username = adjective.capitalize() + subject.capitalize()
+    return username
+
+
+def generate_password(length=10, complictated=True):
+    """
+    We generate a password with default settings. You can overide these by
+    changing the arguments in the function call.
+    """
+    password = ""
+    if complictated:
+        chars = string.ascii_letters + string.digits + string.punctuation
+    else:
+        chars = string.ascii_letters
+    for i in range(0, length):
+        password += random.choice(chars)
+    return password
+
+
+if __name__ == "__main__":
+    # let's do some testing!
+    username_test = generate_username()
+    print(username_test)
+    password_test = generate_password()
+    print(password_test)
+```
+
+And now the GUI code nicely split up in a **model**, **controller** and a **view**.
+The overhead is quite large but it makes the code a lot more scalable.
+
+```python
+import wx
+import login_generator
+import time
+import threading
+import queue
+
+
+class View(wx.Dialog):
+    def __init__(self, controller):
+        wx.Dialog.__init__(self, None, title="Login Generator")
+        self.controller = controller
+        self.full_window = wx.Panel(self)
+        self.full_window_sizer = wx.BoxSizer(wx.VERTICAL)
+        self.full_window_sizer.Add(self.create_top_panel(), 0, wx.EXPAND | wx.ALL, 20)
+        self.full_window_sizer.Add(self.create_bottom_panel(), 0, wx.EXPAND, 0)
+        self.full_window.SetSizer(self.full_window_sizer)
+        self.Show()
+
+    def create_bottom_panel(self):
+        bottom_panel = wx.Panel(self.full_window)
+        bottom_panel_sizer = wx.BoxSizer(wx.HORIZONTAL)
+        self.login_list = wx.ListCtrl(bottom_panel, style=wx.LC_REPORT)
+        self.login_list.Bind(wx.EVT_RIGHT_UP, self.show_popup)
+        self.login_list.InsertColumn(0, 'username', width=200)
+        self.login_list.InsertColumn(1, 'password', width=200)
+        bottom_panel_sizer.Add(self.login_list, 0, wx.EXPAND | wx.ALL, 200)
+        return bottom_panel
+
+    def create_top_panel(self):
+        top_panel = wx.Panel(self.full_window)
+        top_panel_sizer = wx.BoxSizer(wx.HORIZONTAL)
+        self.login_amount = wx.TextCtrl(top_panel)
+        self.login_complex = wx.CheckBox(top_panel, label="complex")
+        self.login_create = wx.Button(top_panel, label="Create")
+        self.login_create.Bind(wx.EVT_BUTTON, self.submit_request)
+        top_panel_sizer.Add(self.login_amount, 1, wx.EXPAND|wx.ALL,0)
+        top_panel_sizer.Add(self.login_complex, 1, wx.EXPAND|wx.ALL,0)
+        top_panel_sizer.Add(self.login_create, 1, wx.EXPAND|wx.ALL,0)
+        top_panel.SetSizer(top_panel_sizer)
+        return top_panel
+    
+    def show_popup(self, event):
+        menu = wx.Menu()
+        menu.Append(1, "Copy selected items")
+        menu.Bind(wx.EVT_MENU, self.copy_items, id=1)
+        self.PopupMenu(menu)
+
+    def copy_items(self, event):
+        selected_items = []
+        for i in range(self.login_list.GetItemCount()):
+            if self.login_list.IsSelected(i):
+                username = selected_items.append(
+                        self.login_list.GetItem(i, 0).GetText()
+                        )
+                password = selected_items.append(
+                        self.login_list.GetItem(i, 1).GetText()
+                        )
+        clipdata = wx.TextDataObject()
+        clipdata.SetText("\n".join(selected_items))
+        wx.TheClipboard.Open()
+        wx.TheClipboard.SetData(clipdata)
+        wx.TheClipboard.Close()
+
+    def submit_request(self, event):
+        amount = self.login_amount.GetValue()
+        complex_bool = self.login_complex.GetValue()
+        try:
+            amount = int(amount)
+        except:
+            amount = 1
+        self.controller.get_new_logins(amount, complex_bool)
+
+    def update_logins(self, login):
+        username, password = login
+        index = self.login_list.InsertItem(0, username)
+        self.login_list.SetItem(index, 1, password)
+
+
+class Controller(object):
+    def __init__(self):
+        self.app = wx.App()
+        self.view = View(self)
+        self.model = Model(self)
+
+    def get_new_logins(self, amount, complex_bool):
+        self.model.generate_login(amount, complex_bool)
+
+    def set_new_logins(self, logins):
+        self.view.update_logins(logins)
+        
+
+class Model(threading.Thread):
+    def __init__(self, controller):
+        threading.Thread.__init__(self, target=self.main)
+        self.controller = controller
+        self.queue = queue.Queue()
+        self.start()
+
+    def main(self):
+        while True:
+            amount, complex_bool = self.queue.get()
+            username = login_generator.generate_username()
+            password = login_generator.generate_password(12, complex_bool)
+            logins = (username, password)
+            self.controller.set_new_logins(logins)
+            time.sleep(1)
+
+    def generate_login(self, amount, complex_bool):
+        for i in range(0, amount):
+            self.queue.put((amount, complex_bool))
+            
+
+if __name__ == "__main__":
+    mvc = Controller()
+    mvc.app.MainLoop()
+```
+
 # Coding challenge - Login generator with GUI
 
 # Coding challenge - Trivial pursuit with GUI