python - csv - take away data of one column from another -

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i want take value of column 4 column 3 (their both integers), have.

with open('classes.csv', 'rt')as f:     reader=csv.reader(f)     people=[]     column in reader:         people.append(column[0:8])  difference = [x[3] x in people] - [x[4] x in people] print(difference)

i error typeerror: unsupported operand type(s) -: 'list' , 'list' when this. know why error can't think of way around it.

any great!

like @peter wood said in comment, need subtract inside of 1 list comprehension, not doing 2 list comprehension results in list - list. need convert numbers.

difference = [int(x[3]) - int(x[4]) x in people]

if want stuff this, better off using numpy or pandas.

using numpy , it's genfromtxt function:

import numpy np people = np.genfromtxt('classes.txt', delimiter=',', dtype=none) difference = people[:, 3] - people[:, 4]

here people 2 dimensional numpy array, first index going on rows, second on columns [:, 3] takes every row of thirds column.

the dtype=none option lets genfromtxt automatically decide type each column, default float.


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