If you need a code editor with syntax highlighting, but don't want something as heavyweight as QsciScintilla, you can use the QSyntaxHighlighter class to apply highlighting to a QPlainTextEdit widget.
This example was based on existing work by Carson Farmer and Christophe Kibleur, and an example on the SciPres wiki. One aspect not addressed by this prior work is handling of Python's triple-quoted strings, which may span multiple lines; the QSyntaxHighlighter documentation includes an example for C++ comments, but those have different beginning and ending delimiters /* ... */, whereas Python's triple-quoted strings have the same delimiter at the beginning and end. These are handled by the match_multiline method and by treating the triple-quotes within strings as an special case --there may be an easier way to do this, but it seems to work pretty well.
I have placed this code under the Modified BSD License because I believe the author intended it to be freely used. However, I don't believe that I originally wrote this example, though I was responsible for migrating it to the Python Wiki. -- DavidBoddie 2017年01月19日 20:34:17
I modified this code to fix a problem when triple-quotes were embedded inside strings. -- Artemio Garza Reyna 2021年08月08日 20:26:00
1 # syntax.py
2
3 import sys
4
5 from PySide2 import QtCore, QtGui, QtWidgets
6
7 def format(color, style=''):
8 """Return a QTextCharFormat with the given attributes.
9 """
10 _color = QtGui.QColor()
11 _color.setNamedColor(color)
12
13 _format = QtGui.QTextCharFormat()
14 _format.setForeground(_color)
15 if 'bold' in style:
16 _format.setFontWeight(QtGui.QFont.Bold)
17 if 'italic' in style:
18 _format.setFontItalic(True)
19
20 return _format
21
22
23 # Syntax styles that can be shared by all languages
24 STYLES = {
25 'keyword': format('blue'),
26 'operator': format('red'),
27 'brace': format('darkGray'),
28 'defclass': format('black', 'bold'),
29 'string': format('magenta'),
30 'string2': format('darkMagenta'),
31 'comment': format('darkGreen', 'italic'),
32 'self': format('black', 'italic'),
33 'numbers': format('brown'),
34 }
35
36
37 class PythonHighlighter (QtGui.QSyntaxHighlighter):
38 """Syntax highlighter for the Python language.
39 """
40 # Python keywords
41 keywords = [
42 'and', 'assert', 'break', 'class', 'continue', 'def',
43 'del', 'elif', 'else', 'except', 'exec', 'finally',
44 'for', 'from', 'global', 'if', 'import', 'in',
45 'is', 'lambda', 'not', 'or', 'pass', 'print',
46 'raise', 'return', 'try', 'while', 'yield',
47 'None', 'True', 'False',
48 ]
49
50 # Python operators
51 operators = [
52 '=',
53 # Comparison
54 '==', '!=', '<', '<=', '>', '>=',
55 # Arithmetic
56 '\+', '-', '\*', '/', '//', '\%', '\*\*',
57 # In-place
58 '\+=', '-=', '\*=', '/=', '\%=',
59 # Bitwise
60 '\^', '\|', '\&', '\~', '>>', '<<',
61 ]
62
63 # Python braces
64 braces = [
65 '\{', '\}', '\(', '\)', '\[', '\]',
66 ]
67
68 def __init__(self, parent: QtGui.QTextDocument) -> None:
69 super().__init__(parent)
70
71 # Multi-line strings (expression, flag, style)
72 self.tri_single = (QtCore.QRegExp("'''"), 1, STYLES['string2'])
73 self.tri_double = (QtCore.QRegExp('"""'), 2, STYLES['string2'])
74
75 rules = []
76
77 # Keyword, operator, and brace rules
78 rules += [(r'\b%s\b' % w, 0, STYLES['keyword'])
79 for w in PythonHighlighter.keywords]
80 rules += [(r'%s' % o, 0, STYLES['operator'])
81 for o in PythonHighlighter.operators]
82 rules += [(r'%s' % b, 0, STYLES['brace'])
83 for b in PythonHighlighter.braces]
84
85 # All other rules
86 rules += [
87 # 'self'
88 (r'\bself\b', 0, STYLES['self']),
89
90 # 'def' followed by an identifier
91 (r'\bdef\b\s*(\w+)', 1, STYLES['defclass']),
92 # 'class' followed by an identifier
93 (r'\bclass\b\s*(\w+)', 1, STYLES['defclass']),
94
95 # Numeric literals
96 (r'\b[+-]?[0-9]+[lL]?\b', 0, STYLES['numbers']),
97 (r'\b[+-]?0[xX][0-9A-Fa-f]+[lL]?\b', 0, STYLES['numbers']),
98 (r'\b[+-]?[0-9]+(?:\.[0-9]+)?(?:[eE][+-]?[0-9]+)?\b', 0, STYLES['numbers']),
99
100 # Double-quoted string, possibly containing escape sequences
101 (r'"[^"\\]*(\\.[^"\\]*)*"', 0, STYLES['string']),
102 # Single-quoted string, possibly containing escape sequences
103 (r"'[^'\\]*(\\.[^'\\]*)*'", 0, STYLES['string']),
104
105 # From '#' until a newline
106 (r'#[^\n]*', 0, STYLES['comment']),
107 ]
108
109 # Build a QRegExp for each pattern
110 self.rules = [(QtCore.QRegExp(pat), index, fmt)
111 for (pat, index, fmt) in rules]
112
113 def highlightBlock(self, text):
114 """Apply syntax highlighting to the given block of text.
115 """
116 self.tripleQuoutesWithinStrings = []
117 # Do other syntax formatting
118 for expression, nth, format in self.rules:
119 index = expression.indexIn(text, 0)
120 if index >= 0:
121 # if there is a string we check
122 # if there are some triple quotes within the string
123 # they will be ignored if they are matched again
124 if expression.pattern() in [r'"[^"\\]*(\\.[^"\\]*)*"', r"'[^'\\]*(\\.[^'\\]*)*'"]:
125 innerIndex = self.tri_single[0].indexIn(text, index + 1)
126 if innerIndex == -1:
127 innerIndex = self.tri_double[0].indexIn(text, index + 1)
128
129 if innerIndex != -1:
130 tripleQuoteIndexes = range(innerIndex, innerIndex + 3)
131 self.tripleQuoutesWithinStrings.extend(tripleQuoteIndexes)
132
133 while index >= 0:
134 # skipping triple quotes within strings
135 if index in self.tripleQuoutesWithinStrings:
136 index += 1
137 expression.indexIn(text, index)
138 continue
139
140 # We actually want the index of the nth match
141 index = expression.pos(nth)
142 length = len(expression.cap(nth))
143 self.setFormat(index, length, format)
144 index = expression.indexIn(text, index + length)
145
146 self.setCurrentBlockState(0)
147
148 # Do multi-line strings
149 in_multiline = self.match_multiline(text, *self.tri_single)
150 if not in_multiline:
151 in_multiline = self.match_multiline(text, *self.tri_double)
152
153 def match_multiline(self, text, delimiter, in_state, style):
154 """Do highlighting of multi-line strings. ``delimiter`` should be a
155 ``QRegExp`` for triple-single-quotes or triple-double-quotes, and
156 ``in_state`` should be a unique integer to represent the corresponding
157 state changes when inside those strings. Returns True if we're still
158 inside a multi-line string when this function is finished.
159 """
160 # If inside triple-single quotes, start at 0
161 if self.previousBlockState() == in_state:
162 start = 0
163 add = 0
164 # Otherwise, look for the delimiter on this line
165 else:
166 start = delimiter.indexIn(text)
167 # skipping triple quotes within strings
168 if start in self.tripleQuoutesWithinStrings:
169 return False
170 # Move past this match
171 add = delimiter.matchedLength()
172
173 # As long as there's a delimiter match on this line...
174 while start >= 0:
175 # Look for the ending delimiter
176 end = delimiter.indexIn(text, start + add)
177 # Ending delimiter on this line?
178 if end >= add:
179 length = end - start + add + delimiter.matchedLength()
180 self.setCurrentBlockState(0)
181 # No; multi-line string
182 else:
183 self.setCurrentBlockState(in_state)
184 length = len(text) - start + add
185 # Apply formatting
186 self.setFormat(start, length, style)
187 # Look for the next match
188 start = delimiter.indexIn(text, start + length)
189
190 # Return True if still inside a multi-line string, False otherwise
191 if self.currentBlockState() == in_state:
192 return True
193 else:
194 return False
Here's a simple editor application that demonstrates it (not including save/load features). Really all you need to do is instantiate the syntax.PythonHighlighter class, passing the QPlainTextEdit widget's document to the constructor:
1 # editor.py
2
3 from PyQt4 import QtGui
4 import syntax
5
6 app = QtGui.QApplication([])
7 editor = QtGui.QPlainTextEdit()
8 highlight = syntax.PythonHighlighter(editor.document())
9 editor.show()
10
11 # Load syntax.py into the editor for demo purposes
12 infile = open('syntax.py', 'r')
13 editor.setPlainText(infile.read())
14
15 app.exec_()