how to add the headers to csv file only one in python

Question

I tried many ways/combinations to insert headers (I need to add two column headers) but the file doesn't accept headers at file creation. At best, I get headers as rows come into the file one after the other. I can't see how to enter the headers only once persistently. Can you see in the code below where I could make some change please? Thanks.

            with open(MYFILE, "w", newline='') as csvWriter, open('read.csv', 'r', newline='') as csvReader:
            if keyword != "q":
                fieldnames = [engine, keyword]
                #fieldnames = ['Engine', 'Keywords']
                # writer = csv.DictWriter(csvWriter, fieldnames=[engine, keyword], extrasaction='ignore')
                writer = csv.DictWriter(csvWriter, fieldnames=fieldnames)
                writer.writeheader()

                reader = csv.DictReader(csvReader, fieldnames=fieldnames)
                writer.writerow({"Engine": engine, "Keywords": keyword})
                writer.writerows(reader)

I'm trying to save data into a csv file. I have two columns but no headers currently. I'd need some column titles like in any spreadsheet basically.

UPDATE ============================================== I've tried to insert to no avail the first block hereafter before and after the 2nd one. There is certainly something I'm not doing right but I don't know. Any suggestion, please?

STATUS = "quit"
print("Press [q] to quit at any time")
menu_engine = {}
menu_engine['1'] = "Google Search - Large Results"
menu_engine['2'] = "Google Search - Small Results"
menu_engine['3'] = "Yahoo Search - Large Results"
menu_engine['4'] = "Yahoo Search - Small Results"

while True:
options = menu_engine.keys()
for entry in options:
    print(entry, menu_engine[entry])
engine = input("Enter your Type of Search: ")

while STATUS != "q":
    keyword = input("Enter keyword(s): ")

    with open(MYFILE, "a", newline='') as csvWriter:
        if keyword != "q":
            fieldnames = [engine, keyword]
            writer = csv.DictWriter(csvWriter, fieldnames=fieldnames, extrasaction='ignore')
            writer.writeheader()

THE EXPECTED OUTPUT in the CSV File:

    Engine Number,Keywords
    4,man man
    4,mate mate

@Chris Doyle. I edited my post. See at the bottom of it. Thanks. — timotom
– timotom, Commented Dec 16, 2019 at 17:59
Can you add sample of the file content and sample expected output — Chris Doyle
– Chris Doyle, Commented Dec 17, 2019 at 0:46

Chris Doyle · Accepted Answer · 2019-12-16 18:18:54Z

1

you write the header with writeheader() then you can just write the rows

import csv
with open('new.dat', "w", newline='') as csvWriter, open('test.dat', 'r', newline='') as csvReader:
        fieldnames = ['Engine', 'Keywords']
        writer = csv.DictWriter(csvWriter, fieldnames=fieldnames)
        reader = csv.DictReader(csvReader, fieldnames=fieldnames)
        writer.writeheader()
        writer.writerows(reader)

INPUT FILE

sef,56
sfd,67
eryt,67
sdfsf,34

OUTPUT FILE

Engine,Keywords
sef,56
sfd,67
eryt,67
sdfsf,34

UPDATE

I felt there should be an easier way to do this and seems you can use fileinput module from the standard python library to edit the same file inplace and insert the record at the start. this will save you having to the move or rename files.

import fileinput
headers = ['Engine','Type']
with fileinput.input('test.dat', inplace=1) as my_file:
    for line in my_file:
        if my_file.isfirstline():
            print(",".join(headers))
        print(line, end='')

edited Dec 16, 2019 at 18:18

answered Dec 16, 2019 at 17:59

Chris Doyle

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6 Comments

timotom Over a year ago

I'm on it. Cheers. I need to make sure I copy 'new.dat' to the 'test.dat' name. I'll use test.csv as I'm on Linux.

Chris Doyle Over a year ago

i feel there must be an easier way than this though as this seems a lot or work just to add a line at the start

Chris Doyle Over a year ago

updated the answer with a way to edit the file inplace and add in the line at the start

timotom Over a year ago

Is the test.dat extension supposed to do something that Linux cannot do or can it just be replaced with a test.csv file?

Chris Doyle Over a year ago

The extention makes no difference. I just call my test file test.dat as I use the same file to test lots of different data. So feel free to use .csv extention

|

Andrei · Accepted Answer · 2021-05-27 06:50:36Z

0

Try:

df["new_column"]=" "
df.to_csv("your_file.csv", index= False)
print(df)      #to see if it's what you need

answered May 27, 2021 at 6:50

Andrei

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