Error: cannot call `vectorize` on size 0 inputs unless `otypes` is set

I tried to connect to twitter API. I have a lookup table looks like:

ID  LAT LON RADIUS
1    XX  XX  XX
2    XX  XX  XX

And then my code is shown below:

for contents in lookup:
    lat=contents[1]
    lon=contents[2]
    radius=contents[3]

    tweets = tw.Cursor(api.search, geocode=(lat,lon,radius)).items(1000)

And then it gives me the error that:

Error: cannot call vectorize on size 0 inputs unless otypes is set

Has anyone met this problem before and do you have any ideas to solve this problem? Thanks in advance!