[Qgis-developer] Few improvements in PyQGIS

[Chris Crook]

Hi Martin

Since you asked, one suggestion for pythonisation(??)   It would be good to have an layers() iterator over map canvas layers something like

for l in iface.mapCanvas().layers():
   ...

Cheers
Chris

-----Original Message-----
From: qgis-developer-bounces at lists.osgeo.org [mailto:qgis-developer-bounces at lists.osgeo.org] On Behalf Of Martin Dobias
Sent: Friday, 5 February 2010 10:24 a.m.
To: qgis-dev
Subject: [Qgis-developer] Few improvements in PyQGIS

Hi all

I hope this is a good news for developers using python. In svn trunk
(r12878) there are few additions that make QGIS API more pythonic.

QgsFeature allows direct access to attributes (get, set, delete attribute):
>>> f = QgsFeature()
>>> f[1] = QVariant("hello")
>>> print f[1].toString()
hello
>>> del f[1]
>>> print f.attributeMap()
{}

QgsVectorLayer and QgsVectorDataProvider support iterating (available for those with sip >= 4.9).

layer.select([], QgsRectangle())
for f in layer:
  # do something with feature f

--- equals to ---

layer.select([], QgsRectangle())
f = QgsFeature()
while layer.nextFeature(f):
  # do something with feature f

That's it. The older idioms (using nextFeature) keep working too.

Inspired by a blog post from Sean Gillies:
http://sgillies.net/blog/952/iterators

Btw. fetching a list of values in an column gets this simple:
>>> lst = [ feat[1] for feat in layer ]
(just don't forget a select() call before iterating)

If you have any tips what other parts of QGIS API could be made more pythonic, let me know.

Martin
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