网格中的 Tkinter label 不必要地扩展

Question

I have a label in a tkinter grid layout which expands when I set its content, even though the label's size is more than sufficient to cover the string.

Label expands with more than enough empty space

I am setting the content of the label via its attached textvariable. As it's a filepath, which is too long, I am truncating the string to a length of 50 characters. When I set the stringVar, the label (and its parent frame) expands. That causes the list element on the left to be squashed.

The label is set in a grid layout whose column is configured to expand. (This is mainly done so that the white label covers the area when no content is set.) However, there is no need for the label to expand, since there is enough space in the label to fit the entire string without expanding. The text covers only ~50% of the label.

What is causing this unnecessary expansion of the label, and how can I prevent this?

Creating the panel:

 def _buildUI(self):
    self._filesPanel = tk.LabelFrame(self._parentFrame, text="Selected file")
    self._filesPanel.grid_columnconfigure(0, weight=0)
    self._filesPanel.grid_columnconfigure(1, weight=1)
    self._filesPanel.grid(row=0, column=0, sticky="news")

    fileNameLabel = tk.Label(self._filesPanel, text="Image file:")
    maskFileNameLabel = tk.Label(self._filesPanel, text="Mask file:")

    self._imageFilePathVar = tk.StringVar()
    self._maskFilePathVar = tk.StringVar()
    self._fileNameLabelSelection = tk.Label(self._filesPanel, textvariable=self._imageFilePathVar, bg="white")
    self._maskFileLabelSelection = tk.Label(self._filesPanel, textvariable=self._maskFilePathVar, bg="white")

    fileNameLabel.grid(row=1, column=0, padx=(5, 5), pady=(2, 2))
    maskFileNameLabel.grid(row=2, column=0, padx=(5, 5), pady=(2, 2))
    self._fileNameLabelSelection.grid(row=1, column=1, sticky="news", padx=(5, 5), pady=(2, 2))
    self._maskFileLabelSelection.grid(row=2, column=1, sticky="news", padx=(5, 5), pady=(2, 2))

Setting the label content:

def loadFilePaths(self, imagePath:str, maskPath:str):
    imageFilePathToDisplay = self._trimStringToElementLength(imagePath)
    self._imageFilePathVar.set(imageFilePathToDisplay)
    maskFilePathToDisplay = self._trimStringToElementLength(maskPath)
    self._maskFilePathVar.set(maskFilePathToDisplay)

def _trimStringToElementLength(self, text: str, maxLength: int = 50) -> str:
    if not text:
        return "N/A"
    if len(text) > maxLength:
        return f"...{text[-maxLength:]}"
    return text

Configuraiton of the parent frames

    self._parentFrame.grid_columnconfigure(0, weight=2)  <--- the weight for the list on the left
    self._parentFrame.grid_columnconfigure(1, weight=5)  <--- the weight for the panel on the right
    self._parentFrame.rowconfigure(0, weight=1)
    self._imageList.getFrame().grid(row=0, column=0, sticky="news", padx=(2, 2))
    self._overlayPanel.grid(row=0, column=1, sticky="news", padx=(2, 2))

Answer 1

@Bryan Oakley's comment was the solution. Setting any width for the label prevents the auto extension. Replace the lines in the _buildUI() function with

    self._fileNameLabelSelection = tk.Label(self._filesPanel, textvariable=self._imageFilePathVar,
                                            bg="white", width=10)
    self._maskFileLabelSelection = tk.Label(self._filesPanel, textvariable=self._maskFilePathVar,
                                            bg="white", width=10)