跳过某些数据行-Python

Question

I have a CSV file with a ton of data that needs to be plotted and sorted and what not. An example of the data is below.

10, 50, 60, 74, 19
10, 55, 68, 93, 10
10, 84, 92, 75, 32
10, 58, 39, 82, 12
20, 15, 12, 84, 35
20, 53, 13, 96, 57
20, 53, 32, 64, 67
20, 56, 31, 29, 18
30, 85, 92, 18, 95
30, 75, 12, 92, 12
...
90, 35, 21, 95, 47
100, 67, 96, 73, 47
100, 86, 32, 62, 32
100, 32, 53, 69, 57
100, 34, 64, 72, 34

What I'm looking for is taking the first row, 4th, row, and 8th row, etc. and putting them into a list. so it looks as such:

column1 = ['10', '20', '30', ..., '100']
column3 = ['60', '12', '92', ..., '73']
column5 = ['19', '35', '95', ..., '47']

Note: the first row from the data set should be in the first column of the output, 2nd row from the data is the 2nd column of output, etc. Also, I want to be able to control which columns I select to put into the lists (and which rows as well).

I'm also looking for a way to adjust which nth row I want to begin with. For example, if we start with row 2, the output would be as such:

column1 = ['10', '20', '30', ..., '100']
column3 = ['68', '13', '12', ..., '32']
column5 = ['10', '35', '12', ..., '32']

This is the code I have so far:

import numpy as np
import matplotlib.pyplot as plt
import csv

column1 = []
column2 = []
column4 = []

with open('csvFile.csv', 'rb') as f:
    w = csv.reader(f, delimiter = ',')
    for i, line in enumerate(w):
        if i == 0 or i == 1:
            pass # Skip first row
        else:
            column1.append(line[1])
            column2.append(line[2])
            column4.append(line[4])

This gives me ALL the values in the columns, which I don't want. Maybe I'm overthinking this, as what I was thinking about doing after was indexing the lists and removing the values I don't want (which my dataset is MUCH larger than what is shown here - I have a total of 26 rows per first number (ie 26 rows of the number 10 with data after it, 26 rows of 20 with data, 26 of 30, etc.))

Answer 1

You can just check whether i is a multiple of four or not. If it is not a multiple of four then skip

with open("data", 'rb') as f:
    w = csv.reader(f,delimiter = ",")
    for i, line in enumerate(w):
        if (i % 4 == 0): 
            column1.append(line[0])
            column2.append(line[1])
            column3.append(line[2])