# Copyright 2008 Nanorex, Inc. See LICENSE file for details. """ ProteinSequenceEditor.py @copyright: 2008 Nanorex, Inc. See LICENSE file for details. @version: $Id$ @author: Urmi History: Urmi copied this from DnaSequenceEditor.py and modified it to suit the requirements of a protein sequence editor. """ import foundation.env as env import os import re import string from PyQt4.Qt import SIGNAL from PyQt4.Qt import QTextCursor from PyQt4.Qt import QString from PyQt4.Qt import QFileDialog from PyQt4.Qt import QMessageBox from PyQt4.Qt import QRegExp from PyQt4.Qt import QTextDocument from PyQt4.Qt import QPalette from PM.PM_Colors import getPalette from PM.PM_Colors import sequenceEditorNormalColor from PM.PM_Colors import sequenceEditorChangedColor from utilities.prefs_constants import workingDirectory_prefs_key from protein.ProteinSequenceEditor.Ui_ProteinSequenceEditor import Ui_ProteinSequenceEditor from utilities import debug_flags from utilities.debug import print_compact_stack class ProteinSequenceEditor(Ui_ProteinSequenceEditor): """ Creates a dockable protein sequence editor. """ validSymbols = QString(' <>~!@#%&_+`=$*()[]{}|^\'"\\.;:,/?') sequenceFileName = None current_protein = None # The current protein chunk. _sequence_changed = False # Set to True when the sequence has been changed by the user. _previousSequence = "" # The previous sequence, just before the user changed it. def __init__(self, win): """ Creates a dockable protein sequence editor """ Ui_ProteinSequenceEditor.__init__(self, win) self.isAlreadyConnected = False self.isAlreadyDisconnected = False self._suppress_textChanged_signal = False self._suppress_cursorPosChanged_signal = False self.connect_or_disconnect_signals(True) self.win = win self.maxSeqLength = 0 def connect_or_disconnect_signals(self, isConnect): """ Connect or disconnect widget signals sent to their slot methods. This can be overridden in subclasses. By default it does nothing. @param isConnect: If True the widget will send the signals to the slot method. @type isConnect: boolean """ if isConnect and self.isAlreadyConnected: if debug_flags.atom_debug: print_compact_stack("warning: attempt to connect widgets"\ "in this PM that are already connected." ) return if not isConnect and self.isAlreadyDisconnected: if debug_flags.atom_debug: print_compact_stack("warning: attempt to disconnect widgets"\ "in this PM that are already disconnected.") return self.isAlreadyConnected = isConnect self.isAlreadyDisconnected = not isConnect if isConnect: change_connect = self.win.connect else: change_connect = self.win.disconnect change_connect(self.loadSequenceButton, SIGNAL("clicked()"), self._open_FASTA_File) change_connect(self.saveSequenceButton, SIGNAL("clicked()"), self._savePeptideSequence) change_connect( self.sequenceTextEdit, SIGNAL("textChanged()"), self._sequenceChanged ) change_connect( self.sequenceTextEdit, SIGNAL("editingFinished()"), self._assignPeptideSequence ) change_connect( self.sequenceTextEdit, SIGNAL("cursorPositionChanged()"), self._cursorPosChanged) change_connect( self.findLineEdit, SIGNAL("textEdited(const QString&)"), self.findLineEdit_textEdited) change_connect( self.findNextToolButton, SIGNAL("clicked()"), self.findNext) change_connect( self.findPreviousToolButton, SIGNAL("clicked()"), self.findPrevious) change_connect( self.replacePushButton, SIGNAL("clicked()"), self.replace) return def update_state(self, bool_enable = True): """ Update the state of this widget by enabling or disabling it depending upon the flag bool_enable. @param bool_enable: If True , enables the widgets inside the sequence editor @type bool_enable: boolean """ for widget in self.children(): if hasattr(widget, 'setEnabled'): if widget.__class__.__name__ != 'QAbstractButton': widget.setEnabled(bool_enable) return def _sequenceChanged( self ): """ Slot for the Protein Sequence textedit widget. (private method) Assumes the sequence changed directly by user's keystroke in the textedit. Other methods... """ if self._suppress_textChanged_signal: return self._suppress_textChanged_signal = True cursorPos = self.getCursorPosition() theSequence = self.getPlainSequence() if len(theSequence) == len(self._previousSequence): # Replace space characters with the same character. aa = self._previousSequence[cursorPos - 1] theSequence.replace(" ", aa) print "The last character was replaced with: ", aa # Insert the sequence; it will be "stylized" by _setSequence(). self._setSequence(theSequence, inCursorPos = cursorPos) if False: # Set to True for debugging statements. if theSequence == self._previousSequence: print "The sequence did not change (YOU SHOULD NEVER SEE THIS)." elif len(theSequence) < len(self._previousSequence): print "Character(s) were deleted from the sequence." elif len(theSequence) == len(self._previousSequence): print "A character was replaced. The sequence length is the same." else: print "Character(s) where added to the sequence." pass # If the sequence in the text edit (field) is different from the current # sequence, change the sequence field bg color to pink to # indicate that the sequence is different. If they are the same, # change the sequence field background (back) to white. if theSequence != self.current_protein.protein.get_sequence_string(): self._sequence_changed = True else: self._sequence_changed = False self._previousSequence = theSequence self._updateSequenceBgColor() #Urmi 20080725: Some time later we need to have a method here which #would allow us to set the sequence of the protein chunk. We will also #update the secondary structure sequence or will it be the same as the #original one? self._suppress_textChanged_signal = False return def _assignPeptideSequence(self): """ (private) Slot for the "editingFinished()" signal generated by the PM_TextEdit whenever the user presses the Enter key in the sequence text edit field. Assigns the amino acid sequence in the sequence editor text field to the current protein. @attention: this method is not implemented yet. If called, it will display a messagebox warning the user that this is not implement yet. """ if not self.current_protein: return sequenceString = self.getPlainSequence() sequenceString = str(sequenceString) #assign sequence only if it not the same as the current sequence seq = self.current_protein.protein.get_sequence_string() if seq != sequenceString: #self.current_protein.setSequence(sequenceString) #self.updateSequence(cursorPos = self.getCursorPosition()) msg = "We are sorry. You cannot change the sequence since "\ "this feature is not yet supported." QMessageBox.warning(self.win, "Warning!", msg) self._suppress_textChanged_signal = False self.updateSequence(self.current_protein) return def _updateSequenceBgColor(self): """ Updates the sequence field background color (pink = changed, white = unchanged). """ if self._sequence_changed: bgColor = sequenceEditorChangedColor else: bgColor = sequenceEditorNormalColor palette = getPalette(None, QPalette.Base, bgColor) self.sequenceTextEdit.setPalette(palette) return def getPlainSequence( self, inOmitSymbols = False ): """ Returns a plain text QString (without HTML stylization) of the current sequence. All characters are preserved (unless specified explicitly), including valid base letters, punctuation symbols, whitespace and invalid letters. @param inOmitSymbols: Omits characters listed in self.validSymbols. @type inOmitSymbols: bool @return: The current Protein sequence in the PM. @rtype: QString """ outSequence = self.sequenceTextEdit.toPlainText() outSequence = outSequence.toUpper() if inOmitSymbols: # This may look like a sloppy piece of code, but Qt's QRegExp # class makes it pretty tricky to remove all punctuation. theString = '[<>' \ + str( QRegExp.escape(self.validSymbols) ) \ + ']|-' outSequence.remove(QRegExp( theString )) return outSequence def clear( self ): """ Clears the sequence editor. """ self.current_protein = None self._setSequenceAndStructure("", "") return def _setSequenceAndStructure(self, inSequence, inStructure, inCursorPos = -1): """ Sets the sequence, structure and ruler fields in the sequence editor. @param inSequence: The sequence string. @type inSequence: QString @param inStructure: The secondary structure string. @type inStructure: QString @param inCursorPos: the position in the sequence in which to place the cursor. If cursorPos is negative, the cursor position is placed at first residue of the sequence (default). @type inCursorPos: int """ #NOTE: It is important that sequence is set last so that setCursorPos() #doesn't complain (i.e. the structure and ruler strings must be #equal to the length of the sequence string before setting the cursor # position). --Mark 2008-12-20 self._setSecondaryStructure(inStructure) self._setRuler(len(inSequence)) self._setSequence(inSequence, inCursorPos = inCursorPos) return def _setSequence( self, inSequence, inStylize = True, inCursorPos = -1 ): """ Replace the current amino acid sequence with the new sequence text. (private method) Callers outside this class wishing to update the amino acid sequence field should call updateSequence(). @param inSequence: The sequence string. @type inSequence: QString @param inStylize: If True, inSequence will be converted from a plain text string (including optional symbols) to an HTML rich text string. @type inStylize: bool @param inCursorPos: the position in the sequence in which to place the cursor. If cursorPos is negative, the cursor position is placed at first residue of the sequence (default). @type inCursorPos: int @see: updateSequence() """ seq = str(inSequence) seq = seq.upper() htmlSequence = self._convertProteinSequenceToColoredSequence(seq) if inStylize: htmlSequence = self._fixedPitchSequence(htmlSequence) self._suppress_textChanged_signal = True self._suppress_cursorPosChanged_signal = True self.sequenceTextEdit.setHtml(htmlSequence) # Generates cursorPosChanged signal! self.setCursorPosition(inCursorPos = inCursorPos) self._suppress_textChanged_signal = False self._suppress_cursorPosChanged_signal = False return def _getFormattedSequence(self, inSequence): """ Create formatted sequence to be used by secondary structure text edit @param inSequence: The new sequence. @type inSequence: QString """ colorList = ['Red','Blue', 'Green'] secStrucList = ['H','E', '-'] secStrucDict = dict(zip(secStrucList, colorList)) outSequence = "" for i in range(len(inSequence)): currentAA = inSequence[i] color = secStrucDict[currentAA] outSequence = outSequence + "" outSequence = outSequence + currentAA + "" #Now put html tags and make everything bold fixedPitchSequence = "" + outSequence fixedPitchSequence += "" return fixedPitchSequence def _setSecondaryStructure(self, inStructure): """ Set the secondary structure of the protein. (private method) Callers outside this class wishing to update the secondary structure field should call updateSequence(). @param inStructure: The structure string. @type inStructure: QString @see: updateSequence() """ fixedPitchSequence = self._getFormattedSequence(inStructure) self.secStrucTextEdit.setHtml(fixedPitchSequence) return def getRulerText(self, lengthOfSeq): """ Return the ruler text given I{lengthOfSeq} (i.e. the length of the current sequence). """ rulerText = "" i = 0 while i < lengthOfSeq: if i == 0: rulerText = "1" i = i + 1 elif i % 10 == 0 and i % 5 == 0: rulerText = rulerText + str(i+1) if len(str(i+1)) == 2: i = i + 2 continue elif len(str(i+1)) == 3: i = i + 3 else: i = i + 1 continue elif i % 5 == 0 and i % 10 != 0: rulerText = rulerText + "*" i = i + 1 else: rulerText = rulerText + "-" i = i + 1 return rulerText def _setRuler(self, lengthOfSeq): """ Set the sequence ruler with a length of I{lengthOfSeq}. Callers outside this class wishing to update the ruler should call updateSequence(). @param lengthOfSeq: length of the sequence. @type lengthOfSeq: int @note: supports up to 3 digits (i.e. max length of 999). """ rulerText = self.getRulerText(lengthOfSeq) fixedPitchSequence = "" + rulerText fixedPitchSequence += "" self.aaRulerTextEdit.setHtml(fixedPitchSequence) return def _convertProteinSequenceToColoredSequence(self, inSequence): """ Create formatted sequence to be used by the sequence editor @param inSequence: The new sequence. @type inSequence: QString """ outSequence = "" colorList = ['Crimson', 'CadetBlue', 'Coral', 'DarkCyan', 'DarkGray', 'DarkGoldenRod', 'DarkOliveGreen', 'BlueViolet', 'Red', 'Chocolate', 'DarkKhaki', 'DarkSalmon', 'DarkSeaGreen', 'FireBrick', 'HotPink', 'LawnGreen', 'IndianRed', 'Indigo', 'LightCoral', 'LightBlue', 'Khaki'] aaList = ['A', 'V', 'X', 'Y', 'W', 'T', 'S', 'P', 'F', 'M', 'K', 'L', 'I' 'H', 'G', 'Q', 'E', 'C', 'R', 'N', 'D' ] aaDict = dict(zip(aaList, colorList)) for i in range(len(inSequence)): currentAA = inSequence[i] try: color = aaDict[currentAA] except KeyError: color = aaDict['X'] outSequence = outSequence + "" outSequence = outSequence + currentAA + "" return outSequence def _colorExtraSequenceCharacters(self, inSequence): """ Returns I{inSequence} with html tags that color any extra overhang characters gray. @param inSequence: The sequence. @type inSequence: QString @return: inSequence with the html tags to color any overhang characters. @rtype: string """ aaLength = self.current_protein.protein.count_amino_acids() if len(inSequence) <= aaLength: return inSequence sequence = inSequence[:aaLength] overhang = inSequence[aaLength:] return sequence + "" + overhang + "" def _fixedPitchSequence(self, sequence): """ Make the sequence 'fixed-pitched' i.e. width of all characters should be constance @param sequence: The new sequence. @type sequence: QString """ fixedPitchSequence = "" + sequence fixedPitchSequence += "" return fixedPitchSequence def getSequenceLength( self ): """ Returns the number of characters in the sequence textedit widget. """ theSequence = self.getPlainSequence( inOmitSymbols = True ) outLength = theSequence.length() return outLength def updateSequence(self, proteinChunk = None, inCursorPos = -1): """ Updates the sequence editor with the sequence of I{proteinChunk}. @param proteinChunk: the protein chunk. If proteinChunk is None (default), the sequence editor is cleared. @type proteinChunk: protein Chunk @param inCursorPos: the position in the sequence in which to place the cursor. If cursorPos is negative, the cursor position is placed at first residue of the sequence (default). @type inCursorPos: int """ if proteinChunk: assert isinstance(proteinChunk, self.win.assy.Chunk) and \ proteinChunk.isProteinChunk() self.current_protein = proteinChunk else: # Use self.current_protein. Make sure it's not None. #assert isinstance(self.current_protein, self.win.assy.Chunk) and \ #proteinChunk.isProteinChunk() self.clear() return # We have a protein chunk. Update the editor with its sequence. sequence = self.current_protein.protein.get_sequence_string() structure = self.current_protein.protein.get_secondary_structure_string() self._setSequenceAndStructure(sequence, structure, inCursorPos = inCursorPos) # Update the bg color to white. self._sequence_changed = False self._previousSequence = sequence self._updateSequenceBgColor() # Update window title with name of current protein. titleString = 'Sequence Editor for ' + self.current_protein.name self.setWindowTitle(titleString) if not self.isVisible(): #Show the sequence editor if it isn't visible. #ATTENTION: the sequence editor will (temporarily) close the #Reports dockwidget (if it is visible). The Reports dockwidget #is restored when the sequence Editor is closed. self.show() return def setCursorPosition(self, inCursorPos = -1): """ Set the cursor position to I{cursorPos} in the sequence textedit widget. @param inCursorPos: the position in the sequence in which to place the cursor. If cursorPos is negative, the cursor position is placed at the beginning of the sequence (default). @type inCursorPos: int """ # Make sure cursorPos is in the valid range. if inCursorPos < 0: cursorPos = 0 anchorPos = 1 elif inCursorPos >= self.getSequenceLength(): cursorPos = self.getSequenceLength() - 1 anchorPos = self.getSequenceLength() else: cursorPos = inCursorPos anchorPos = inCursorPos + 1 # Useful print statements for debugging. if 0: print "setCursorPosition(): Sequence=", self.getPlainSequence() print "Final inCursorPos=%d\ncursorPos=%d, anchorPos=%d" % \ (inCursorPos, cursorPos, anchorPos) self._suppress_cursorPosChanged_signal = True # Finally, set the cursor position in the sequence. cursor = self.sequenceTextEdit.textCursor() cursor.setPosition(anchorPos, QTextCursor.MoveAnchor) cursor.setPosition(cursorPos, QTextCursor.KeepAnchor) self.sequenceTextEdit.setTextCursor( cursor ) cursorMate = self.secStrucTextEdit.textCursor() cursorMate.setPosition(anchorPos, QTextCursor.MoveAnchor) cursorMate.setPosition(cursorPos, QTextCursor.KeepAnchor) self.secStrucTextEdit.setTextCursor( cursorMate ) cursorMate2 = self.aaRulerTextEdit.textCursor() cursorMate2.setPosition(anchorPos, QTextCursor.MoveAnchor) cursorMate2.setPosition(cursorPos, QTextCursor.KeepAnchor) self.aaRulerTextEdit.setTextCursor( cursorMate2 ) self._updateToolTip() self._suppress_cursorPosChanged_signal = False return def getCursorPosition( self ): """ Returns the cursor position in the sequence textedit widget. """ cursor = self.sequenceTextEdit.textCursor() return cursor.position() def _cursorPosChanged( self ): """ Slot called when the cursor position of the sequence textEdit changes. When this happens, this method also changes the cursor position of the 'Mate' text edit. Because of this, both the text edit widgets in the Sequence Editor scroll 'in sync'. """ if self._suppress_cursorPosChanged_signal: return cursor = self.sequenceTextEdit.textCursor() cursorPos = cursor.position() if 0: print "_cursorPosChanged(): cursorPos=", cursorPos self.setCursorPosition(inCursorPos = cursorPos) # sets all three. # Provide amino acid info as cursor position changes env.history.statusbar_msg("") current_command = self.win.commandSequencer.currentCommand commandSet = ('EDIT_PROTEIN', 'EDIT_RESIDUES') if current_command.commandName not in commandSet: return aa_index = min(cursorPos, self.getSequenceLength() - 1) if current_command.commandName == 'EDIT_PROTEIN': current_command.propMgr.setCurrentAminoAcid(aa_index) if current_command.commandName == 'EDIT_RESIDUES': current_command.propMgr._sequenceTableCellChanged(aa_index, 0) current_command.propMgr.sequenceTable.setCurrentCell(aa_index, 3) self._updateToolTip() return def _updateToolTip(self): """ Update the tooltip text (and status bar) with the current residue id. """ aa_index = self.current_protein.protein.get_current_amino_acid_index() aa_info = self.current_protein.protein.get_amino_acid_id(aa_index) aa_id, residue_id = aa_info.strip().split(":") toolTipText = residue_id self.sequenceTextEdit.setToolTip(str(toolTipText)) env.history.statusbar_msg(toolTipText) return def _display_and_recenter(self, index): """ Display and recenter the view on the current amino acid under the cursor in the text edit @param index: index of amino acid under cursor in sequence text edit @type index: int @note: this method has no callers. It will likely be moved to EditResidues_PM soon. -Mark 2008-12-20 """ chunk = self.current_protein chunk.protein.collapse_all_rotamers() current_aa = chunk.protein.get_amino_acid_at_index(index) if current_aa: if self.win.commandSequencer.currentCommand.commandName == 'EDIT_RESIDUES': checked = self.win.commandSequencer.currentCommand.propMgr.recenterViewCheckBox.isChecked() if checked: ca_atom = current_aa.get_c_alpha_atom() if ca_atom: self.win.glpane.pov = -ca_atom.posn() self.win.glpane.gl_update() return def _open_FASTA_File(self): """ Open (read) the user specified FASTA sequence file and load it into the sequence field. @TODO: It only reads in the first line of the file. Also, it doesn't handle any special cases. (Once the special cases are clearly defined, that functionality will be added. @attention: This is not implemented yet. """ #Urmi 20080714: should not this be only fasta file, for both load and save if self.parentWidget.assy.filename: odir = os.path.dirname(self.parentWidget.assy.filename) else: odir = env.prefs[workingDirectory_prefs_key] self.sequenceFileName = \ str(QFileDialog.getOpenFileName( self, "Load FASTA sequence for " + self.current_protein.name, odir, "FASTA file (*.txt);;All Files (*.*);;")) lines = self.sequenceFileName try: lines = open(self.sequenceFileName, "rU").readlines() except: print "Exception occurred to open file: ", self.sequenceFileName return sequence = lines[0] sequence = QString(sequence) sequence = sequence.toUpper() self._setSequence(sequence) return def _write_FASTA_File(self, fileName, sequence): """ Writes I{sequence} in FASTA format to I{filename}. @param fileName: full path of the file. @type fileName: str @param sequence: AA sequence to be saved in FASTA format. @type sequence: str @attention: The sequence is not written in FASTA format yet. @TODO: Write sequence in FASTA format. """ try: f = open(fileName, "w") except: print "Exception occurred to open file %s to write: " % fileName return None f.write(str(sequence)) f.close() return def _savePeptideSequence(self): """ Save the current sequence (displayed in the sequence field) in FASTA format in the specified file. """ if not self.sequenceFileName: sdir = env.prefs[workingDirectory_prefs_key] else: sdir = self.sequenceFileName fileName = QFileDialog.getSaveFileName( self, "Save Sequence As ...", sdir, "FASTA File (*.txt)" ) if fileName: fileName = str(fileName) if fileName[-4] != '.': fileName += '.txt' if os.path.exists(fileName): # ...and if the "Save As" file exists... # ... confirm overwrite of the existing file. ret = QMessageBox.warning( self, "Save Sequence...", "The file \"" + fileName + "\" already exists.\n"\ "Do you want to overwrite the existing file or cancel?", "&Overwrite", "&Cancel", "", 0, # Enter == button 0 1 ) # Escape == button 1 if ret == 1: # The user cancelled return # write the current set of element colors into a file self._write_FASTA_File( fileName, str(self.sequenceTextEdit.toPlainText())) return # ==== Methods to support find and replace. # Should this (find and replace) be in its own class? -- Ninad 2007-11-28 def findNext(self): """ Find the next occurence of the search string in the sequence """ self._findNextOrPrevious() return def findPrevious(self): """ Find the previous occurence of the search string in the sequence """ self._findNextOrPrevious(findPrevious = True) return def _findNextOrPrevious(self, findPrevious = False): """ Find the next or previous matching string depending on the findPrevious flag. It also considers into account various findFlags user might have set (e.g. case sensitive search) @param findPrevious: If true, this method will find the previous occurance of the search string. @type findPrevious: boolean """ findFlags = QTextDocument.FindFlags() if findPrevious: findFlags |= QTextDocument.FindBackward if self.caseSensitiveFindAction.isChecked(): findFlags |= QTextDocument.FindCaseSensitively if not self.sequenceTextEdit.hasFocus(): self.sequenceTextEdit.setFocus() searchString = self.findLineEdit.text() cursor = self.sequenceTextEdit.textCursor() found = self.sequenceTextEdit.find(searchString, findFlags) #May be the cursor reached the end of the document, set it at position 0 #to redo the search. This makes sure that the search loops over as #user executes findNext multiple times. if not found: if findPrevious: sequence_QString = self.sequenceTextEdit.toPlainText() newCursorStartPosition = sequence_QString.length() else: newCursorStartPosition = 0 cursor.setPosition( newCursorStartPosition, QTextCursor.MoveAnchor) self.sequenceTextEdit.setTextCursor(cursor) found = self.sequenceTextEdit.find(searchString, findFlags) #Display or hide the warning widgets (that say 'sequence not found' #based on the boolean 'found' self._toggleWarningWidgets(found) return def _toggleWarningWidgets(self, found): """ If the given searchString is not found in the sequence string, toggle the display of the 'sequence not found' warning widgets. Also enable or disable the 'Replace' button accordingly @param found: Flag that decides whether to sho or hide warning @type found: boolean @see: self.findNext, self.findPrevious """ if not found: self.findLineEdit.setStyleSheet(self._getFindLineEditStyleSheet()) self.phraseNotFoundLabel.show() self.warningSign.show() self.replacePushButton.setEnabled(False) else: self.findLineEdit.setStyleSheet("") self.phraseNotFoundLabel.hide() self.warningSign.hide() self.replacePushButton.setEnabled(True) return def findLineEdit_textEdited(self, searchString): """ Slot method called whenever the text in the findLineEdit is edited *by the user* (and not by the setText calls). This is useful in dynamically searching the string as it gets typed in the findLineedit. @param searchString: string that is searched for @type searchString: str """ self.findNext() #findNext sets the focus inside the sequenceTextEdit. So set it back to #to the findLineEdit to permit entering more characters. if not self.findLineEdit.hasFocus(): self.findLineEdit.setFocus() return def replace(self): """ Find a string matching the searchString given in the findLineEdit and replace it with the string given in the replaceLineEdit. """ searchString = self.findLineEdit.text() replaceString = self.replaceLineEdit.text() sequence = self.sequenceTextEdit.toPlainText() #Its important to set focus on the sequenceTextEdit otherwise, #cursor.setPosition and setTextCursor won't have any effect if not self.sequenceTextEdit.hasFocus(): self.sequenceTextEdit.setFocus() cursor = self.sequenceTextEdit.textCursor() selectionStart = cursor.selectionStart() selectionEnd = cursor.selectionEnd() sequence.replace( selectionStart, (selectionEnd - selectionStart), replaceString ) cursor.setPosition((selectionEnd -1), QTextCursor.MoveAnchor) self.sequenceTextEdit.setTextCursor(cursor) #Set the sequence in the text edit. self._setSequence(sequence) #Find the next occurance of the 'seqrchString' in the sequence. self.findNext() return