How to export resulted data to CSV file using python script?

Question

I have a CSV file which contains multiple Row and columns. Based on the if condition I need to filter the date and I want to write that filtered data to new CSV file.

So I have written this below code for the same however I'm getting only one row but we have many rows in the filtered data.

Could you please help me to fix the issue.

Code:

import CSV

with open('testfilename.csv','r') ad file

   csv_reader = csv.reader (csv_file)
   rows = [ row for row in csv_reader]

   filtered_rows1 = []
   filtered_rows2 = []

   for row in rows:

      if(row[3] == "CRITICAL"):
         filtered_rows1.append(row)
         with open('Critical.csv','w', newline='') as csv_file
            csv_writer = CSV.writer(csv_file)
               for row in filtered_rows1:
                  csv_writerow(row)
       elif(row[3] == "URGENT"):
         filtered_rows2.append(row)
         with open('Urgent.csv','w', newline='') as csv_file
            csv_writer = CSV.writer(csv_file)
               for row in filtered_rows2:
                  csv_writerow(row)

awarrier99 · Accepted Answer · 2022-12-29 06:55:33Z

Your issue is most likely that you are opening the file testfilenameV1.csv in write mode every time you add a row. This means that the file will be truncated each time (existing contents will be deleted). You should either open the file in append mode (pass 'a' instead of 'w' as the second argument to open), or you should open the file outside of your for row in myFile loop so that it's only truncated at the beginning of the script, rather than during each iteration when your if condition passes.

I'm also not exactly sure whether it's a problem that you're creating a new CSV writer each time, but I would suggest moving the myFile2 = csv.writer(file2) line outside of your for loop as well.

Overall this could look something like this:

import csv

with open('testfilename.csv', 'r') as file:
   myFile = csv.reader(file)
   with open('testfilenameV1.csv', 'w', newline='') as file2:
       myFile2 = csv.writer(file2)

       for row in myFile:
           if row[3] == "CRITICAL":
               myFile2.writerow(row)

kibromhft · Accepted Answer · 2022-12-29 07:03:06Z

0

The code needs a little refactoring.

import csv

with open('testfilename.csv', 'r') as csv_file:

  csv_reader = csv.reader(csv_file)

  # Store the rows in a list
  rows = [row for row in csv_reader]

# Create a new list to store the filtered rows
filtered_rows = []

# Iterate over the rows in the list
for row in rows:
  # Check if the row meets the desired condition
  if row[3] == 'CRITICAL':
    # If the row meets the condition, append it to the filtered rows list
    filtered_rows.append(row)

with open('testfilenameV1.csv', 'w', newline='') as csv_file:
  csv_writer = csv.writer(csv_file)
  for row in filtered_rows:
    csv_writer.writerow(row)

answered Dec 29, 2022 at 7:03

kibromhft

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3 Comments

awarrier99 Over a year ago

I do agree this looks cleaner overall as it avoids the multiple nestings, but the reason I didn't go for an approach like this is that it will also cause the entire set of rows to be stored in memory, and it requires iterating the rows 3 times, whereas the original structure only stores one row in memory at a time and only needs to iterate once. Depending on the size of the file, this could be impactful

Mahesh Aknur Over a year ago

For the same report if I have 2 filters and I'm trying with the below code but .not getting accurate results. Can you please help with multiple filters for the same report like if row[3] = 'CRITICAL' Aand if row[3] = 'URGENT'

kibromhft Over a year ago

Here, you are trying to apply a filter across several categories of data, all of which are based on the same column. Using a Pandas dataframe in such a case would be a suitable way to accomplish that.

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