SFrames: Converting str to int or float

Question

I am starting to learn SFrames data structure lately. I wonder if anyone experienced the problem of converting a "str" column to "float" or "int" column. In R, I could easily accomplish the task by as.numeric() or as.integer().

How could I do that in SFrames (python)?

Thanks,

Answer 1

I've found this approach works.

sf['column_name'] = sf['column_name'].astype(float)
sf['column_name'] = sf['column_name'].astype(str)

Answer 2

This doesn't work sometimes specially for empty columns. Its better to assign first to either string or float and then load elements. Example

sf['column'] = ""  #for string
sf['column1'] = numpy.nan  #for float

and then load values. I got struck in similar situation.