在python 2.7中将特定行从csv复制到csv

Question

So far I have been trying to copy specific rows including headers from original csv file to a new one. However, once I run my code it was copying a total mess creating a huge document.

This is one of the options I have tried so far, which seems to be the closest to the solution:

import csv
with open('D:/test.csv', 'r') as f,open('D:/out.csv', 'w') as f_out:
     reader = csv.DictReader(f)
     writer = csv.writer(f_out)
     for row in reader:
         if row["ICLEVEL"] == "1":
            writer.writerow(row)

The thing is that I have to copy only those rows where value of "ICLEVEL"(Header name) is equal to "1".

Note: test.csv is very huge file and I cannot hardcode all header names in the writer.

Any demostration of pythonic way of doing this is greatly appreciated. Thanks.

Answer 1

writer.writerow expects a sequence (a tuple or list). You can use DictWriter which expects a dict .

import csv
with open('D:/test.csv', 'r') as f, open('D:/out.csv', 'w') as f_out:
    reader = csv.DictReader(f)
    writer = csv.DictWriter(f_out, fieldnames=reader.fieldnames)
    writer.writeheader()  # For writing header
    for row in reader:
        if row['ICLEVEL'] == '1':
            writer.writerow(row)

Answer 2

Your row is a dictionary. CSV writer cannot write dictionaries. Select the values from the dictionary and write just them:

writer.writerow(reader.fieldnames)
for row in reader:
  if row["ICLEVEL"] == "1":
    values = [row[field] for field in reader.fieldnames]
    writer.writerow(values)

Answer 3

I would actually use Pandas, not a CSV reader:

import pandas as pd

df=pd.read_csv("D:/test.csv")
newdf = df[df["ICLEVEL"]==1]
newdf.to_csv("D:/out.csv",index=False)

The code is much more compact.