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
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
|
# -*- coding: utf-8 -*-
"""
***************************************************************************
__init__.py
---------------------
Date : May 2014
Copyright : (C) 2014 by Nathan Woodrow
Email : woodrow dot nathan at gmail dot com
***************************************************************************
* *
* This program is free software; you can redistribute it and/or modify *
* it under the terms of the GNU General Public License as published by *
* the Free Software Foundation; either version 2 of the License, or *
* (at your option) any later version. *
* *
***************************************************************************
"""
__author__ = 'Nathan Woodrow'
__date__ = 'May 2014'
__copyright__ = '(C) 2014, Nathan Woodrow'
# This will get replaced with a git SHA1 when you do a git archive
__revision__ = '$Format:%H$'
from qgis.PyQt.QtCore import QCoreApplication, NULL
import inspect
import string
from qgis._core import *
def register_function(function, arg_count, group, usesgeometry=False, referenced_columns=[QgsFeatureRequest.AllAttributes], **kwargs):
"""
Register a Python function to be used as a expression function.
Functions should take (values, feature, parent) as args:
Example:
def myfunc(values, feature, parent):
pass
They can also shortcut naming feature and parent args by using *args
if they are not needed in the function.
Example:
def myfunc(values, *args):
pass
Functions should return a value compatible with QVariant
Eval errors can be raised using parent.setEvalErrorString("Error message")
:param function:
:param arg_count:
:param group:
:param usesgeometry:
:return:
"""
class QgsExpressionFunction(QgsExpression.Function):
def __init__(self, func, name, args, group, helptext='', usesgeometry=True, referencedColumns=QgsFeatureRequest.AllAttributes, expandargs=False):
QgsExpression.Function.__init__(self, name, args, group, helptext, usesgeometry, referencedColumns)
self.function = func
self.expandargs = expandargs
def func(self, values, feature, parent):
try:
if self.expandargs:
values.append(feature)
values.append(parent)
return self.function(*values)
else:
return self.function(values, feature, parent)
except Exception as ex:
parent.setEvalErrorString(str(ex))
return None
helptemplate = string.Template("""<h3>$name function</h3><br>$doc""")
name = kwargs.get('name', function.__name__)
helptext = kwargs.get('help_text') or function.__doc__ or ''
helptext = helptext.strip()
expandargs = False
if arg_count == "auto":
# Work out the number of args we need.
# Number of function args - 2. The last two args are always feature, parent.
args = inspect.getargspec(function).args
number = len(args)
arg_count = number - 2
expandargs = True
register = kwargs.get('register', True)
if register and QgsExpression.isFunctionName(name):
if not QgsExpression.unregisterFunction(name):
msgtitle = QCoreApplication.translate("UserExpressions", "User expressions")
msg = QCoreApplication.translate("UserExpressions", "The user expression {0} already exists and could not be unregistered.").format(name)
QgsMessageLog.logMessage(msg + "\n", msgtitle, QgsMessageLog.WARNING)
return None
function.__name__ = name
helptext = helptemplate.safe_substitute(name=name, doc=helptext)
f = QgsExpressionFunction(function, name, arg_count, group, helptext, usesgeometry, referenced_columns, expandargs)
# This doesn't really make any sense here but does when used from a decorator context
# so it can stay.
if register:
QgsExpression.registerFunction(f)
return f
def qgsfunction(args='auto', group='custom', **kwargs):
"""
Decorator function used to define a user expression function.
Example:
@qgsfunction(2, 'test'):
def add(values, feature, parent):
pass
Will create and register a function in QgsExpression called 'add' in the
'test' group that takes two arguments.
or not using feature and parent:
Example:
@qgsfunction(2, 'test'):
def add(values, *args):
pass
"""
def wrapper(func):
return register_function(func, args, group, **kwargs)
return wrapper
class QgsEditError(Exception):
def __init__(self, value):
self.value = value
def __str__(self):
return repr(self.value)
# Define a `with edit(layer)` statement
class edit:
def __init__(self, layer):
self.layer = layer
def __enter__(self):
assert self.layer.startEditing()
return self.layer
def __exit__(self, ex_type, ex_value, traceback):
if ex_type is None:
if not self.layer.commitChanges():
raise QgsEditError(self.layer.commitErrors())
return True
else:
self.layer.rollBack()
return False
|
