Display of a large amount of data in a Canvas with a Scrollbar - python-3.x

Question

I'm having a problem trying to display a large table in tkinter.
First, I tried to display all label at once in the canvas, but over few hundred rows, the program shut down. So I tried to create a scrollable canvas that updates everytime I scroll: I collect the position of the scrollbar and depending on the position of it, I display the 10 values corresponding.
But I can't get this code working. For now it only displays a black background with the scrollbar on the right.
Here is the code:
from tkinter import *
class Application(object):
def __init__(self, parent):
self.x = []
for i in range(1, 1000):
self.x.append(i)
self.parent = parent
self.mainFrame = Frame(self.parent)
self.mainFrame.pack()
self.canvas = Canvas(self.mainFrame, width = 200, height = 500, bg = "black")
self.canvas.grid(row = 0, column = 0)
self.scroll = Scrollbar(self.mainFrame, orient = VERTICAL, command = self.update)
self.scroll.grid(row = 0, column = 1)
self.canvas.configure(yscrollcommand = self.scroll.set)
self.tabCursor = 0
self.scrollPosition = self.scroll.get()
def update(self):
self.tabCursor = round(self.scrollPosition[0]*len(self.x))
if ((len(self.x) - self.tabCursor) < 10):
self.tabCursor = len(self.x) - 10
for i in range(0, 10): #display 10 values
label = Label(self.canvas, text = str(self.x[tabCursor + i]), width = 50)
label.grid(column = 0, row = i)
if __name__ == '__main__':
root = Tk()
app = Application(root)
root.mainloop()
EDIT :
I finally had time to implement your answer. It looks fine but I can't get the scrollbar working and i don't know why.
class TableauDeDonnees(object):
"Tableau de données -- Onglet Tableau de données"
def __init__(self, data, parent):
self.parent = parent
self.data = data
print(self.data[0], self.data[1])
print(len(self.data[0]), len(self.data[1]))
self.labels = []
self.navigationFrame = Frame(self.parent)
self.canvas = Canvas(self.parent, bg = "black", width = 200, height = 500)
self.mainFrame = Frame(self.canvas)
self.navigationFrame.pack()
print(len(data))
for row in range(50):
for column in range(len(data)):
self.labels.append(Label(self.canvas, text = str(data[column][row])))
for i in range(len(self.labels)):
self.labels[i].grid(row = i // 2, column = i % 2, sticky = NSEW)
self.boutonRetour = Button(self.navigationFrame, text = "Retour", command = lambda: self.move(-2))
self.quickNav = Entry(self.navigationFrame, width = 3)
self.quickNav.bind('<Return>', lambda x: self.move(self.quickNav.get()))
self.boutonSuivant = Button(self.navigationFrame, text = "Suivant", command = lambda: self.move(0))
temp = divmod(len(data[0]), len(self.labels) // 2)
self.pages = temp[0] + (1 if temp[1] else 0)
self.position = Label(self.navigationFrame, text='Page 1 sur ' + str(self.pages))
self.pageCourante = 1
self.boutonRetour.grid(row = 0, column = 0)
self.quickNav.grid(row = 0, column = 1)
self.boutonSuivant.grid(row = 0, column = 2)
self.position.grid(row = 0, column = 3)
self.scroll = Scrollbar(self.parent, orient = VERTICAL, command = self.canvas.yview)
self.canvas.configure(yscrollcommand = self.scroll.set)
self.scroll.pack(side = RIGHT, fill='y')
self.canvas.pack(side = LEFT, fill = 'both')
self.canvas.create_window((4,4), window = self.mainFrame, anchor = "nw", tags = "frame")
self.canvas.configure(yscrollcommand = self.scroll.set)
self.mainFrame.bind("<Configure>", self.update)
self.canvas.configure(scrollregion = self.canvas.bbox("all"))
def update(self, event):
self.canvas.configure(scrollregion = self.canvas.bbox("all"))
def move(self, direction):
if (self.pageCourante == 1 and direction == -2) or (self.pageCourante == self.pages and direction == 0):
return
if direction in (-2, 0):
self.pageCourante += direction + 1
else:
try:
temp = int(direction)
if temp not in range(1, self.pages + 1):
return
except ValueError:
return
else:
self.pageCourante = temp
for i in range(len(self.labels)):
try:
location = str(self.data[i % 2][len(self.labels)*(self.pageCourante - 1) + i])
except IndexError:
location = ''
self.labels[i].config(text = location)
self.position.config(text = 'Page ' + str(self.pageCourante) + ' sur ' + str(self.pages))
I don't understand why the scrollbar isn't working properly. Note, that my parent is a notebook.
Also, there is a problem with the number of items displayed. The number of pages is right but it seems it displays more than it should cause last pages are empty and the last values displayed seems right.
Thank you for your attention

Answer 1

The scrollbar doesn't work by continuously creating new widgets ad infinitum. You were also missing some key parts - unfortunately, Scrollbar isn't as straightforward as most tkinter widgets.
from tkinter import *
class Application(object):
def __init__(self, parent):
self.parent = parent
self.canvas = Canvas(self.parent, bg='black', width = 200, height = 500)
self.mainFrame = Frame(self.canvas)
self.scroll = Scrollbar(self.parent, orient = VERTICAL, command=self.canvas.yview)
self.canvas.configure(yscrollcommand=self.scroll.set)
self.scroll.pack(side='right', fill='y')
self.canvas.pack(side='left', fill='both')
self.canvas.create_window((4,4), window=self.mainFrame, anchor="nw", tags="frame")
self.canvas.configure(yscrollcommand = self.scroll.set)
self.mainFrame.bind("<Configure>", self.update)
self.x = []
for i in range(1000):
self.x.append(Label(self.mainFrame, text=str(i)))
self.x[i].grid()
def update(self, event):
self.canvas.configure(scrollregion=self.canvas.bbox("all"))
if __name__ == '__main__':
root = Tk()
app = Application(root)
root.mainloop()
If you'd like to show only a few at a time and provide a forum-like interface, you can use Buttons to navigate between pages. This example allows the user to navigate with Back and Forward buttons, as well as by entering a page number in the box and pressing Enter.
from tkinter import *
class Application(object):
def __init__(self, parent):
self.x = list(range(1000))
self.labels = []
self.parent = parent
self.navigation_frame = Frame(self.parent)
self.canvas = Canvas(self.parent, bg='black', width = 200, height = 500)
self.mainFrame = Frame(self.canvas)
self.navigation_frame.pack()
for i in range(100):
self.labels.append(Label(self.mainFrame, text=str(i)))
self.labels[i].grid()
self.back_button = Button(self.navigation_frame, text='Back', command=lambda: self.move(-2))
self.quick_nav = Entry(self.navigation_frame, width=3)
self.quick_nav.bind('<Return>', lambda x: self.move(self.quick_nav.get()))
self.forward_button = Button(self.navigation_frame, text='Forward', command=lambda: self.move(0))
temp = divmod(len(self.x), len(self.labels))
self.pages = temp[0] + (1 if temp[1] else 0)
self.you_are_here = Label(self.navigation_frame, text='Page 1 of ' + str(self.pages))
self.current_page = 1
self.back_button.grid(row=0, column=0)
self.quick_nav.grid(row=0, column=1)
self.forward_button.grid(row=0, column=2)
self.you_are_here.grid(row=0, column=3)
self.scroll = Scrollbar(self.parent, orient = VERTICAL, command=self.canvas.yview)
self.canvas.configure(yscrollcommand=self.scroll.set)
self.scroll.pack(side='right', fill='y')
self.canvas.pack(side='left', fill='both')
self.canvas.create_window((4,4), window=self.mainFrame, anchor="nw", tags="frame")
self.canvas.configure(yscrollcommand = self.scroll.set)
self.mainFrame.bind("<Configure>", self.update)
def update(self, event):
self.canvas.configure(scrollregion=self.canvas.bbox("all"))
def move(self, direction):
if (self.current_page == 1 and direction == -2) or (self.current_page == self.pages and direction == 0):
return
if direction in (-2, 0):
self.current_page += direction + 1
else:
try:
temp = int(direction)
if temp not in range(1, self.pages+1):
return
except ValueError:
return
else:
self.current_page = temp
for i in range(len(self.labels)):
try:
location = str(self.x[len(self.labels)*(self.current_page - 1) + i])
except IndexError:
location = ''
self.labels[i].config(text=location)
self.you_are_here.config(text='Page ' + str(self.current_page) + ' of ' + str(self.pages))
if __name__ == '__main__':
root = Tk()
app = Application(root)
root.mainloop()