def str_get(arr, i):
 f = (lambda x: (x[i] if (len(x) > i) else np.nan))
 return _na_map(f, arr)

def str_get ( arr , i ) : f = ( lambda x : ( x [ i ] if ( len ( x ) > i ) else np . nan ) ) return _na_map ( f , arr )
extract element from lists .