1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
|
##############################################################################
#
# Copyright (c) 2001, 2002 Zope Foundation and Contributors.
# All Rights Reserved.
#
# This software is subject to the provisions of the Zope Public License,
# Version 2.1 (ZPL). A copy of the ZPL should accompany this distribution.
# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY AND ALL EXPRESS OR IMPLIED
# WARRANTIES ARE DISCLAIMED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF TITLE, MERCHANTABILITY, AGAINST INFRINGEMENT, AND FITNESS
# FOR A PARTICULAR PURPOSE.
#
##############################################################################
"""Generic Python Expression Handler
"""
class PythonExpr(object):
"""
Evaluates a python expression by calling :func:`eval` after
compiling it with :func:`compile`.
"""
def __init__(self, name, expr, engine):
"""
:param str expr: The Python expression.
:param ExpressionEngine engine: The expression compiler that
is creating us.
"""
text = '\n'.join(expr.splitlines()) # normalize line endings
text = '(' + text + ')' # Put text in parens so newlines don't matter
self.text = text
try:
code = self._compile(text, '<string>')
except SyntaxError as e:
raise engine.getCompilerError()(str(e))
self._code = code
self._varnames = code.co_names
def _compile(self, text, filename):
return compile(text, filename, 'eval')
def _bind_used_names(self, econtext, builtins):
# Construct a dictionary of globals with which the Python
# expression should be evaluated.
names = {}
vars = econtext.vars
marker = self
if not isinstance(builtins, dict):
builtins = builtins.__dict__
for vname in self._varnames:
val = vars.get(vname, marker)
if val is not marker:
names[vname] = val
elif vname not in builtins:
# Fall back to using expression types as variable values.
val = econtext._engine.getTypes().get(vname, marker)
if val is not marker:
val = ExprTypeProxy(vname, val, econtext)
names[vname] = val
names['__builtins__'] = builtins
return names
def __call__(self, econtext):
__traceback_info__ = self.text
vars = self._bind_used_names(econtext, __builtins__)
return eval(self._code, vars)
def __str__(self):
return 'Python expression "%s"' % self.text
def __repr__(self):
return '<PythonExpr %s>' % self.text
class ExprTypeProxy(object):
'''Class that proxies access to an expression type handler'''
def __init__(self, name, handler, econtext):
self._name = name
self._handler = handler
self._econtext = econtext
def __call__(self, text):
return self._handler(self._name, text,
self._econtext._engine)(self._econtext)
|
