QPlainTextEdit consume large memory for large string - pyqt

Question

I am have written small application in which dictionary contain large string but when I used to display string into QPlainTextEdit it consume large memory and my application is crashed.
is there any effective to update text into Qplaintextedit
size of string 464.6005735397339
Line # Mem usage Increment Line Contents
================================================
807 1556.8 MiB 1556.8 MiB #profile
808 def load_violation_data(self, a="", b=""):
809 """
810 update
811 into.
812 """
813 1556.8 MiB 0.0 MiB self.clear_selection()
814 1556.8 MiB 0.0 MiB domain_obj = self.list_widget.selectedItems()[0]
815 1556.8 MiB 0.0 MiB domain_obj.setBackground(QBrush(QColor("#8A2BE2")))
816 1556.8 MiB 0.0 MiB self.app.setOverrideCursor(Qt.WaitCursor)
817 1556.8 MiB 0.0 MiB data = self.violation_data[domain_obj.text()]
818 1556.8 MiB 0.0 MiB print (sys.getsizeof(data)/1024**2)
819 4532.4 MiB 2975.6 MiB self.plain_textedit.setPlainText(data)
820 4532.4 MiB 0.0 MiB self.violation_label.setText(self.vio_dm.get_output_file_prefix(domain_obj.text()))
821 4532.4 MiB 0.0 MiB self.app.restoreOverrideCursor()

Answer 1

Without knowing the structure of the file, it's difficult to determine a valid approach to properly split the data in batches.
The concept, though, is fundamentally the same: define a maximum amount of loadable data and only set the text to a specified chunk of that data.
In the following example, the viewer has a default 5mb limit (which can be adjusted), and it just seeks the file cursor position to a limit×page, then reads the content up to the size limit and displays it in the plain text edit.
from PyQt5 import QtCore, QtGui, QtWidgets
class LargeFileView(QtWidgets.QWidget):
def __init__(self, path=None, parent=None):
super().__init__(parent)
layout = QtWidgets.QVBoxLayout(self)
tools = QtWidgets.QHBoxLayout()
layout.addLayout(tools)
style = self.style()
self.startButton = QtWidgets.QToolButton(
icon=style.standardIcon(style.SP_MediaSkipBackward))
self.prevButton = QtWidgets.QToolButton(
icon=style.standardIcon(style.SP_MediaSeekBackward))
self.pageSpin = QtWidgets.QSpinBox(minimum=1, keyboardTracking=False)
self.nextButton = QtWidgets.QToolButton(
icon=style.standardIcon(style.SP_MediaSeekForward))
self.endButton = QtWidgets.QToolButton(
icon=style.standardIcon(style.SP_MediaSkipForward))
self.sizeSpin = QtWidgets.QSpinBox(minimum=1, maximum=10, value=5,
suffix='MB', keyboardTracking=False)
tools.addWidget(self.startButton)
tools.addWidget(self.prevButton)
tools.addWidget(self.pageSpin)
tools.addWidget(self.nextButton)
tools.addWidget(self.endButton)
tools.addWidget(QtWidgets.QFrame(frameShape=QtWidgets.QFrame.VLine))
limitLabel = QtWidgets.QLabel('Size limit:')
tools.addWidget(limitLabel)
limitLabel.setBuddy(self.sizeSpin)
tools.addWidget(self.sizeSpin)
tools.addStretch()
font = QtGui.QFont()
font.setFamily('monospace')
self.plainTextEdit = QtWidgets.QPlainTextEdit(readOnly=True, font=font)
layout.addWidget(self.plainTextEdit)
self.pageSize = 5 * 1024 ** 2
if path:
self.loadFile(path)
self.pageSpin.valueChanged.connect(lambda p: self.goToPage(p - 1))
self.startButton.clicked.connect(lambda: self.goToPage(0))
self.endButton.clicked.connect(lambda: self.goToPage(-1))
self.prevButton.clicked.connect(lambda: self.stepBy(-1))
self.nextButton.clicked.connect(lambda: self.stepBy(1))
self.sizeSpin.valueChanged.connect(self._loadFile)
def loadFile(self, path):
if not QtCore.QFile.exists(path):
return
self.currentFile = QtCore.QFile(path)
self.currentFile.open(QtCore.QIODevice.ReadOnly)
self._loadFile()
def _loadFile(self):
self.currentPage = -1
self.fileSize = self.currentFile.size()
self.pageSize = self.sizeSpin.value() * 1024 ** 2
self.pageCount = self.fileSize // self.pageSize + 1
with QtCore.QSignalBlocker(self.pageSpin):
self.pageSpin.setValue(1)
self.pageSpin.setMaximum(self.pageCount)
self.pageSpin.setSuffix(' / {}'.format(self.pageCount))
self.goToPage(0)
def stepBy(self, step):
self.goToPage(self.currentPage + step)
def goToPage(self, page):
if page < 0:
page = self.pageCount - 1
if self.currentPage == page:
return
self.currentPage = page
self.pageSpin.setValue(page + 1)
if self.currentFile.seek(self.pageSize * page):
text = str(self.currentFile.read(self.pageSize), 'utf-8')
self.plainTextEdit.setPlainText(text)
app = QtWidgets.QApplication([])
test = LargeFileView('/your/very/big/file')
test.show()
app.exec()