OpenRefine Jython / Python expression to conditionally merge columns

openrefine_jython_merge_columns.py

'''
This jython expression merges columns that are named sequentially, 
but only if there is data in the column.
Trying to merge columns with GREL that include empty cells results in an error.
My data included columns like this:

    Title 1 | Title 2 .. | .. Title 14
	----
	My Title | Other Title | etc.

And I wanted values in a single cell separated by newlines like this:

	Joined Titles
	----
	My Title
	My Other Title

Blank cells in a column return a KeyError, so try/except clauses
leave blank cells blank.

This was helpful: https://github.com/OpenRefine/OpenRefine/wiki/Jython

To run this, in the example of Title columns above, select Title 1> Edit Cells> Transform 
	then select Python/Jython in the language dropdown, and paste the script in the text box.
	Make sure that "Title" is changed to whatever your column names are and that the 
	range of sequence numbers reflects how many you have.
Once it's run you can delete the extra sequence columns if you want.
'''
_columns = []
for num in range(2,15):
	_columns.append("Title %s" % (num))
	
try:
	title1 = cells["Title 1"]["value"]
except KeyError:
	title1 = None

for _column in _columns:
	try:
		if cells[_column]["value"]:
			title1 = "%s \n %s" % (title1, cells[_column]["value"])
	except KeyError:
		pass

return title1

'''
Here's a version where I had speakers in 4 separate columns and I wanted them joined by "; "

_columns = []
for num in range(2,5):
    _columns.append("speakers %s" % (num))
	
try:
    name1 = cells["speakers 1"]["value"]
except KeyError:
    name1 = None

for _column in _columns:
    try:
        if cells[_column]["value"]:
            name1 = "%s; %s" % (name1, cells[_column]["value"])
    except KeyError:
        pass

return name1
'''