Trying to use LIKE in an expression in pyQgis

Question

I want to select elements from a layer. The field I use is a string/character field. My code is as follows:

expr = QgsExpression(ur'"myField" = \'valueILookFor\'')
it = myLayer.getFeatures(QgsFeatureRequest(expr))
ids = [i.id() for i in it]
myLayer.setSelectedFeatures (ids)

I do know that the error lies in the first line, as I've already used the rest of the code (which is from stackexchange) for selecting values.

Apparently this does not select any value. I have tried to replace the "=" with a "LIKE" without more success.

score 4 · Accepted Answer · answered Jan 27 '16 at 14:58

You can also use triple-quoted strings, this means you can leave your double quotes and single quotes (apostrophes) un-escaped.

Can make things a little tricky to maintain, so if you can, leave one space padding at the start and end, like so

expr = QgsExpression(""" "my_field" like '%something%' """)

Joseph · Answer 2 · 2016-01-27T14:46:53.987

2

Try something like this:

expr = QgsExpression( " \"myField\"= 'valueILookFor' " )

or

expr = QgsExpression( " \"myField\" LIKE 'valueILookFor' " )

Have to be careful with the quotes. Also, you can just use u'string instead of ur'string'.

edited Jan 27 '16 at 14:46

answered Jan 27 '16 at 14:12

Joseph

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Does not work either. I tried various combinaisons of these. – François Jan 27 '16 at 14:18
2

does it work with a triple quoted string? expr = QgsExpression( """ "myField"= 'valueILookFor' """) – Steven Kay Jan 27 '16 at 14:24
@François - Apologies, I missed out the single quotes as it initially worked for numbers. Should work now for strings also. – Joseph Jan 27 '16 at 14:37
@StevenKay - The triple quote method should also work, consider posting your comment as an answer =) – Joseph Jan 27 '16 at 14:40
YES ! Thanks Steven, your method works ! Thanks a lot :) ! Post it so I can mark it as answered. – François Jan 27 '16 at 14:55

Trying to use LIKE in an expression in pyQgis

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