PyQt WikiIf 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--there may be an easier way to do this, but it seems to work pretty well, although it still has trouble with triple-quotes embedded inside another string (as you'll see if you run the example editor.py below).
1 # syntax.py
2
3 import sys
4
5 from PyQt4.QtCore import QRegExp
6 from PyQt4.QtGui import QColor, QTextCharFormat, QFont, QSyntaxHighlighter
7
8 def format(color, style=''):
9 """Return a QTextCharFormat with the given attributes.
10 """
11 _color = QColor()
12 _color.setNamedColor(color)
13
14 _format = QTextCharFormat()
15 _format.setForeground(_color)
16 if 'bold' in style:
17 _format.setFontWeight(QFont.Bold)
18 if 'italic' in style:
19 _format.setFontItalic(True)
20
21 return _format
22
23
24 # Syntax styles that can be shared by all languages
25 STYLES = {
26 'keyword': format('blue'),
27 'operator': format('red'),
28 'brace': format('darkGray'),
29 'defclass': format('black', 'bold'),
30 'string': format('magenta'),
31 'string2': format('darkMagenta'),
32 'comment': format('darkGreen', 'italic'),
33 'self': format('black', 'italic'),
34 'numbers': format('brown'),
35 }
36
37
38 class PythonHighlighter (QSyntaxHighlighter):
39 """Syntax highlighter for the Python language.
40 """
41 # Python keywords
42 keywords = [
43 'and', 'assert', 'break', 'class', 'continue', 'def',
44 'del', 'elif', 'else', 'except', 'exec', 'finally',
45 'for', 'from', 'global', 'if', 'import', 'in',
46 'is', 'lambda', 'not', 'or', 'pass', 'print',
47 'raise', 'return', 'try', 'while', 'yield',
48 'None', 'True', 'False',
49 ]
50
51 # Python operators
52 operators = [
53 '=',
54 # Comparison
55 '==', '!=', '<', '<=', '>', '>=',
56 # Arithmetic
57 '\+', '-', '\*', '/', '//', '\%', '\*\*',
58 # In-place
59 '\+=', '-=', '\*=', '/=', '\%=',
60 # Bitwise
61 '\^', '\|', '\&', '\~', '>>', '<<',
62 ]
63
64 # Python braces
65 braces = [
66 '\{', '\}', '\(', '\)', '\[', '\]',
67 ]
68 def __init__(self, document):
69 QSyntaxHighlighter.__init__(self, document)
70
71 # Multi-line strings (expression, flag, style)
72 # FIXME: The triple-quotes in these two lines will mess up the
73 # syntax highlighting from this point onward
74 self.tri_single = (QRegExp("'''"), 1, STYLES['string2'])
75 self.tri_double = (QRegExp('"""'), 2, STYLES['string2'])
76
77 rules = []
78
79 # Keyword, operator, and brace rules
80 rules += [(r'\b%s\b' % w, 0, STYLES['keyword'])
81 for w in PythonHighlighter.keywords]
82 rules += [(r'%s' % o, 0, STYLES['operator'])
83 for o in PythonHighlighter.operators]
84 rules += [(r'%s' % b, 0, STYLES['brace'])
85 for b in PythonHighlighter.braces]
86
87 # All other rules
88 rules += [
89 # 'self'
90 (r'\bself\b', 0, STYLES['self']),
91
92 # Double-quoted string, possibly containing escape sequences
93 (r'"[^"\\]*(\\.[^"\\]*)*"', 0, STYLES['string']),
94 # Single-quoted string, possibly containing escape sequences
95 (r"'[^'\\]*(\\.[^'\\]*)*'", 0, STYLES['string']),
96
97 # 'def' followed by an identifier
98 (r'\bdef\b\s*(\w+)', 1, STYLES['defclass']),
99 # 'class' followed by an identifier
100 (r'\bclass\b\s*(\w+)', 1, STYLES['defclass']),
101
102 # From '#' until a newline
103 (r'#[^\n]*', 0, STYLES['comment']),
104
105 # Numeric literals
106 (r'\b[+-]?[0-9]+[lL]?\b', 0, STYLES['numbers']),
107 (r'\b[+-]?0[xX][0-9A-Fa-f]+[lL]?\b', 0, STYLES['numbers']),
108 (r'\b[+-]?[0-9]+(?:\.[0-9]+)?(?:[eE][+-]?[0-9]+)?\b', 0, STYLES['numbers']),
109 ]
110
111 # Build a QRegExp for each pattern
112 self.rules = [(QRegExp(pat), index, fmt)
113 for (pat, index, fmt) in rules]
114
115
116 def highlightBlock(self, text):
117 """Apply syntax highlighting to the given block of text.
118 """
119 # Do other syntax formatting
120 for expression, nth, format in self.rules:
121 index = expression.indexIn(text, 0)
122
123 while index >= 0:
124 # We actually want the index of the nth match
125 index = expression.pos(nth)
126 length = expression.cap(nth).length()
127 self.setFormat(index, length, format)
128 index = expression.indexIn(text, index + length)
129
130 self.setCurrentBlockState(0)
131
132 # Do multi-line strings
133 in_multiline = self.match_multiline(text, *self.tri_single)
134 if not in_multiline:
135 in_multiline = self.match_multiline(text, *self.tri_double)
136
137
138 def match_multiline(self, text, delimiter, in_state, style):
139 """Do highlighting of multi-line strings. ``delimiter`` should be a
140 ``QRegExp`` for triple-single-quotes or triple-double-quotes, and
141 ``in_state`` should be a unique integer to represent the corresponding
142 state changes when inside those strings. Returns True if we're still
143 inside a multi-line string when this function is finished.
144 """
145 # If inside triple-single quotes, start at 0
146 if self.previousBlockState() == in_state:
147 start = 0
148 add = 0
149 # Otherwise, look for the delimiter on this line
150 else:
151 start = delimiter.indexIn(text)
152 # Move past this match
153 add = delimiter.matchedLength()
154
155 # As long as there's a delimiter match on this line...
156 while start >= 0:
157 # Look for the ending delimiter
158 end = delimiter.indexIn(text, start + add)
159 # Ending delimiter on this line?
160 if end >= add:
161 length = end - start + add + delimiter.matchedLength()
162 self.setCurrentBlockState(0)
163 # No; multi-line string
164 else:
165 self.setCurrentBlockState(in_state)
166 length = text.length() - start + add
167 # Apply formatting
168 self.setFormat(start, length, style)
169 # Look for the next match
170 start = delimiter.indexIn(text, start + length)
171
172 # Return True if still inside a multi-line string, False otherwise
173 if self.currentBlockState() == in_state:
174 return True
175 else:
176 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_()