如何使用if语句将数据写入csv列表

Question

I am trying to write data to a csv to a new field/column with if statements (based on values already present in the list). I have a list of UIDs (Field name Class): ACRW, AOC, IFSE, LN, RLW, etc,

This is what I have so far:

import csv
with open('PythonProject.csv', 'r') as rd_list:
    csv_reader = csv.reader(rd_list)
    with open ('new_rdlist.csv', 'w', newline='') as new_csvfile:
        fieldnames = ['Class', 'Description', 'Flex']
        csv_writer = csv.DictWriter (new_csvfile, fieldnames=fieldnames)
        csv_writer.writeheader()
        csv_writer = csv.writer(new_csvfile)
        Class = ''
        for row in csv_reader:
            if Class == 'C':
                value = 'Cable'
            elif Class == 'W':
                value = 'Wave'
            elif Class == 'RT':
                value = 'Therm'
            elif Class == 'H':
                value = 'Heat'
            else:
                value = 'Unit'
            csv_writer.writerow(row)            
input('\nNew List is in your directory, Press Enter to exit')

Expected result is to have the csv populate to be, Class, Description, Flex (which is the new field) (ACRW, unique name, Unit) (AOC, unique name, Unit) (C, unique name, Cable) (IFSE, unique name, Unit) (LN, unique name, Unit) (RLW, unique name, Unit) (W, unique name, Wave) etc...

Answer 1

I hope I understood you right, I assume you intend to read in the "PythonProject.csv" and write the same data with an additional column to "new_rdlist.csv" .

Accessing & Manipulating the data

The main issue seems to be understanding rows in DictReader and DictWriter . As you are already using DictWriter I suggest using the DictReader class as well. The cells/fields in each row can be accessed by their column names. You can access the "Class" value that way, so the first check would read:

if row["Class"] == "C":
  value = "Cable"

you can even directly manipulate the row dictionary:

if row["Class"] == "C":
  row["Flex"] = "Cable"

After that modification the rest should be easy to solve!

Other issues

csv_writer = csv.writer(new_csvfile) is redundant as it overwrites the csv_writer variable again

(Almost) final code

import csv
with open('PythonProject.csv', 'r') as rd_list:
    csv_reader = csv.DictReader(rd_list)
    with open ('new_rdlist.csv', 'w', newline='') as new_csvfile:
        fieldnames = ['Class', 'Description', 'Flex']
        csv_writer = csv.DictWriter (new_csvfile, fieldnames=fieldnames)
        csv_writer.writeheader()
        for row in csv_reader:
            if row["Class"] == "C":
                row["Flex"] = "Cable"
            ...
                row["Flex"] = "Unit"
            csv_writer.writerow(row)            
input('\nNew List is in your directory, Press Enter to exit')