How to solve a tkinter memory leak? - button

Question

I have a dynamic table with a fixed row number (like a FIFO Queue), which updates continuously through tkinter's after() function. Inside the table is a Button, which text is editable.
To make the Button's text editable I used the solution of BrenBarn and reference a loop variable into a function call at the command-attribute.
When the function update_content_items() is cycled, I found, that the memory usage is increasing MB by MB per second. I can confirm that after commenting out the lambda expression, the memory leak was gone. (as seen live running 'top' in the terminal)
It seems I have to use the lambda, otherwise the Button will have a wrong index and the user edits the wrong row, when I just used self.list_items[i], though the user clicked the right one.
Is there a way to solve the problem? How can the user click the right button and edit it while having the right index and getting rid of the leak?
The corresponding code:
def update_content_items(self):
"""
Continuously fills and updates the Table with rows and content.
The size of the table rows is initially fixed by an external value at config.ini
:return: nothing
"""
if len(self.list_items) > self.queueMaxlen:
self.queueMaxlen = len(self.list_items)
self.build_table()
try:
for i in range(len(self.list_items)):
item = self.list_items[i]
self.barcodeImgList[i].image = item.plateimage
orig_image = Image.open(io.BytesIO(item.plateimage))
ein_image = ImageTk.PhotoImage(orig_image)
self.barcodeImgList[i].configure(image=ein_image)
# keeps a reference, because somehow tkinter forgets it...??? Bug of my implementation???
self.barcodeImgList[i].image = ein_image
orig_image = None
ein_image = None
#FIXME Memory LEAK?
self.numberList[i].configure(text=item.number,
command=lambda K=i: self.edit_barcode(self.list_items[K]))
self.timestampList[i].configure(text=item.timestamp)
self.search_hitlist[i].config(bg='white', cursor="xterm")
self.search_hitlist[i].unbind("<Button-1>")
if item.queryresult is not None:
if item.queryresult.gesamtstatus != 'Gruen':
self.search_hitlist[i].insert(tk.END, item.queryresult.barcode +
'\n' + item.queryresult.permitlevel)
self.search_hitlist[i].configure(bg='red', cursor="hand2")
self.search_hitlist[i].bind("<Button-1>", item.url_callback)
else:
self.search_hitlist[i].configure(bg='green', cursor="xterm")
self.search_hitlist[i].configure(state=tk.DISABLED)
self.on_frame_configure(None)
self.canvas.after(10, self.update_content_items)
except IndexError as ie:
for number, thing in enumerate(self.list_items):
print(number, thing)
raise ie
def edit_barcode(self, item=None):
"""
Opens the number plate edit dialogue and updates the corresponding list item.
:param item: as Hit DAO
:return: nothing
"""
if item is not None:
new_item_number = EditBarcodeEntry(self.master.master, item)
if new_item_number.mynumber != 0:
item.number = new_item_number.mynumber
self.list_items.request_work(item, 'update')
self.list_items.edit_hititem_by_id(item)
self.parent.master.queryQueue.put(item)
else:
print("You shouldn't get here at all. Please see edit_barcode function.")
EDIT: It seems there is indeed a deeper memory leak (python itself). The images won't get garbage collected. Memory is slowly leaking in Python 3.x and I do use PIL. Also here: Image loading by file name memory leak is not properly fixed
What can I do, because I have to cycle through a list with records and update Labels with images? Is there a workaround? PhotoImage has no explicit close() function, and if I call del, the reference is gc'ed and no configuring of the Label possible.

Answer 1

an example of my proposed changes, with indentation fixed:
def update_content_items(self):
"""
Continuously fills and updates the Table with rows and content.
The size of the table rows is initially fixed by an external value at config.ini
:return: nothing
"""
if len(self.list_items) > self.queueMaxlen:
self.queueMaxlen = len(self.list_items)
self.build_table()
try:
for i in range(len(self.list_items)):
item = self.list_items[i]
self.barcodeImgList[i].image = item.plateimage
orig_image = Image.open(io.BytesIO(item.plateimage))
ein_image = ImageTk.PhotoImage(orig_image)
self.barcodeImgList[i].configure(image=ein_image)
# keeps a reference, because somehow tkinter forgets it...??? Bug of my implementation???
self.barcodeImgList[i].image = ein_image
orig_image = None
ein_image = None
self.numberList[i].configure(text=item.number) # removed lambda
self.numberList[i].bind("<Button-1>", self.edit_barcode_binding) # added binding
self.timestampList[i].configure(text=item.timestamp)
self.search_hitlist[i].config(bg='white', cursor="xterm")
self.search_hitlist[i].unbind("<Button-1>")
if item.queryresult is not None:
if item.queryresult.gesamtstatus != 'Gruen':
self.search_hitlist[i].insert(tk.END, item.queryresult.barcode +
'\n' + item.queryresult.permitlevel)
self.search_hitlist[i].configure(bg='red', cursor="hand2")
self.search_hitlist[i].bind("<Button-1>", item.url_callback)
else:
self.search_hitlist[i].configure(bg='green', cursor="xterm")
self.search_hitlist[i].configure(state=tk.DISABLED)
self.on_frame_configure(None)
self.canvas.after(10, self.update_content_items)
except IndexError as ie:
for number, thing in enumerate(self.list_items):
print(number, thing)
raise ie
def edit_barcode_binding(self, event): # new wrapper for binding
K = self.numberList.index(event.widget) # get index from list
self.edit_barcode(self.list_items[K]) # call the original function
def edit_barcode(self, item=None):
"""
Opens the number plate edit dialogue and updates the corresponding list item.
:param item: as Hit DAO
:return: nothing
"""
if item is not None:
new_item_number = EditBarcodeEntry(self.master.master, item)
if new_item_number.mynumber != 0:
item.number = new_item_number.mynumber
self.list_items.request_work(item, 'update')
self.list_items.edit_hititem_by_id(item)
self.parent.master.queryQueue.put(item)
else:
print("You shouldn't get here at all. Please see edit_barcode function.")