graphlab create dropna does not work

Question

I'm testing graphlabe create with following

sf=gl.SFrame(['t1','t2','','t3','','t4'])
sf.dropna()

accoding to graphlab api

the above should remove empty values(na), but actually it does not, and no errors given either. anyone knows why?

Answer 1

Your '' is either None nor NaN:

import math

print(None == '')
print(float('nan')=='')
print(math.isnan(float('nan')))

Output:

False
False
True

Doku: dropna()

Remove missing values from an SFrame. A missing value is either None or NaN.

Your value '' is neither so it stays.