I have a CSV file (A.csv) has many columns. The question is how to modify and save a column in this file and database (data.db). I would like to replace the value 1 in column y based on the previous value:
Output:A = [ d x y z
0 1 2 5
1 2 1 9
2 8 1 2
3 3 40 7
4 6 1 7
5 4 30 3]
The expected answer should be :Output:A = [ d x y z
0 1 2 5
1 2 2 9
2 8 2 2
3 3 40 7
4 6 40 7
5 4 30 3]
import csv import numpy as np import numpy import pandas as pd conn = sqlite3.connect('data.db') conn.text_factory = str cur = conn.cursor() A = cur.execute("SELECT * FROM CH1_data") data = cur.execute('UPDATE CH2_data t1 SET y = (SELECT t2.y FROM CH2_data t2 WHERE t2.d < t1.d AND t2.y <> 1 ORDER BY t2.d DESC LIMIT 1) WHERE y = "" ') conn.commit() with open('output_data1001.csv', 'w') as f: writer = csv.writer(f) writer.writerow(['d', 'x','y','z']) writer.writerows(A)It does not work. Please help me.......