Hi, guys, I want to use express to delete the polygons of which the string attribute value is “N”. However, it doesn't work.

Can you kindly help to take a look and suggest a solution?

Thanks!

Ji

The problem is that using == to test for string equality doesn't work so well. You should use strcmp() instead:
strcmp(prims(opinputpath(“.”, 0), $PR, “str”), “N”) == 0
You could also shorten your expression by just using the local variable:
strcmp($STR, “N”) == 0

hi, Graham, thanks a lot for your prompt help!

Hi, graham and other Houdinese,

May I ask how to do the same using Python script?

Thanks!

Python has proper string comparisons using == so you'd do something like this:
hou.pwd().curPrim().attribValue(“str”) == “N”
In many cases you could bypass that long bit of code by using lvar(“STR”) on the left hand side, however lvar only returns floats, so it is not useful in this case where your attribute is a string.

Thank you very much for your advice, graham!