Function editor can i use string-operators

Question

In the Function editor I'm trying to edit a string something like:

from qgis.core import *
from qgis.gui import *
@qgsfunction(args='auto', group='Custom')
def testfunc2(value1, value2, feature, parent):
 s =trim(value1 + value2)
 return s

I get the error:

Eval Error:
global name 'trim' is not defined

Can I use functions like trim, concat etc. in the Function editor?

Answer 1

Yes you can.

The problem is, that there is no method trim available. But there is a method strip() available on every string. You probably want to do

s = value1 + value2 # Concat
s = s.strip() # Trim

In general, you need to import functions. So if you did not import the function trim, it will not be available.

• JAS: Thanks, but how do I import functions like trim etc. I tried all the Qgis libraries like QGis.Utils.
• Matthias Kuhn: Why do you think that there should be a function trim in QGIS? Normally, if it's not geo-specific, read the python documentation or look for generic python modules and if you look for geo-specific stuff read the pyqgis cookbook
• JAS: I didn't but I hoped. In the QGis Expression dialog (2.12.3) you can use these functions for a regular expression. So I assumed they were also usable in the function editor which is also in the Expression Dialog.
• Matthias Kuhn: Expression functions are not usable in the function editor. The function editor is pure python. But no reason to worry, python covers way more functionality than there are expression functions.
• JAS: I found some good documented examples of python code in apps\python27\lib\string.py. Thank you for your time and quick response.