to slice columns in a tuple present in a numpy array
list, numpy, python, tuples
Solution
What `np.genfromtext` has created for you is not an array of tuples, which would have had `object` dtype, but a record array. You can tell from the weird dtype:
dtype=[('f0', '<i4'), ('f1', '<f8'), ('f2', '<f8'), ('f3', 'S19')]
Each of the tuples in that list holds the name of the corresponding field, and its dtype, `<i4` is a little endian 4 byte integer, `<f8` a little endian 8 byte float and `S19` a 19 character long string. You can access the fields by name as:
In [2]: x['f0']
Out[2]: array([ 534, 650, 675, 715, 2884, 3799, 4549, 4819])
In [3]: x['f1']
Out[3]:
array([ 116.48482, 116.4978 , 116.31873, 116.70027, 116.67727,
116.29838, 116.48405, 116.42967])
Problem
I have imported a text file into a numpy array as shown below. ``` data=np.genfromtxt(f,dtype=None,delimiter=',',names=None) ``` where f contains the path of my csv file now data contains the following. ``` array([(534, 116.48482, 39.89821, '2008-02-03 00:00:49'), (650, 116.4978, 39.98097, '2008-02-03 00:00:02'), (675, 116.31873, 39.9374, '2008-02-03 00:00:04'), (715, 116.70027, 40.16545, '2008-02-03 00:00:45'), (2884, 116.67727, 39.88201, '2008-02-03 00:00:48'), (3799, 116.29838, 40.04533, '2008-02-03 00:00:37'), (4549, 116.48405, 39.91403, '2008-02-03 00:00:42'), (4819, 116.42967, 39.93963, '2008-02-03 00:00:43')], dtype=[('f0', '<i4'), ('f1', '<f8'), ('f2', '<f8'), ('f3', 'S19')]) ``` If i now try to column slice, ie extract the first or the second column using ``` data[:,0] ``` It says "too many indices". I figured out that it is due the the way it is being stored. all the rows are being stored as tuples and not as list/array. I thought of using the "ugliest" way possible to perform slicing without having to use iteration. That would be to convert the tuples in each row to list and put it back to the numpy array. something like this ``` data=np.asarray([list(i) for i in data]) ``` But for the above problem, i am losing the datatypes of each column. Each element will be stored as a string rather than integer or float which was automatically detected in the former case. Now if i want to slice the columns without having to use iteration is there any way?