python - NameError: global name 'find' is not defined -

i'm newbie of python. i'm struggling python.

i want limit region (longitude , latitude)

i = find((d[:, 2] >= -120.)            & (d[:, 2] <= -110.)            & (d[:, 3] >= -75.)            & (d[:, 3] <= -71.)) 

but error occurred.

---> 21     = find((d[:, 2]>=-120.) & (d[:, 2]<=-110.) & (d[:, 3]>=-75.) & (d[:, 3]<=-71.))      22     mn = mean(d[i, :], axis=0)      23     std = std(d[i, :], axis=0, ddof=1) nameerror: global name 'find' not defined 

why error occurred? how can solve problem?

thanks in advance.