Excuse me, but how can I get the first item after col.str.split() ?

[Binger-cn]

I need to extract the first part from a string field like ' a,b,c', 'd,e,f' , and the expected result will be 'a', 'd' .

vaex.from_arrays(a=['a,b,c','d,e,f']).a.str.split(',',1).apply(lambda x:x[0])

this code works, but apply() is very slow for millions of rows.

Can I achieve it in a fast way ? like: a.str.split(',',1).struct.get(0) ?