delete all .csv file content in python

Question

so, my program will replace the old data with new data which is the program will put in same .csv file. and after i run the program it is not replaced. below is my code.

                        TEXTFILE = open("data.csv", "w")

                        for i in book_list:
                            TEXTFILE.write("{},{},{},{}".format(i[0],i[1],i[2],i[3]))

                        TEXTFILE.close()

book_list is the list that save new data to stored the result i got:

k,k,45,c
a,a,65,r
d,s,65,r
as,as,65,r
df,df6,65,r
as,as,6,r
as,as,46,r
as,as,45,r
as,as,56,rk,k,45,r
a,a,65,r
d,s,65,r
as,as,65,r
df,df6,65,r
as,as,6,r
as,as,46,r
as,as,45,r
as,as,56,r

it stored to csv with combining old and new content.

well the origininal file is looks like this:

k,k,45,r
a,a,65,r
d,s,65,r
as,as,65,r
df,df6,65,r
as,as,6,r
as,as,46,r
as,as,45,r
as,as,56,r

idk how to explain. but I expect that the result will change one line with new data in the fourth row. for example, the previous line is k,k,45,r (line 1). and the program will change it become k,k,45,c that way

hope you all can help me :)

If you could please post what the original file looks like, and your expected output, that would help — R Nar
– R Nar, Commented Nov 3, 2017 at 18:59
Also post the expected "new content". It would also be helpful to know what the variable book_list looks like. — R Nar
– R Nar, Commented Nov 3, 2017 at 19:23
@KevinJulianto that is very strange. I cannoit reproduce your issue at all. Could it be that the problem is in other part of your code? For example maybe you somehow duplicate contents of book_list. Please make sure that book_list has what you want it to. — UpmostScarab
– UpmostScarab, Commented Nov 3, 2017 at 19:35
nope, I just want to write the new data into the same csv file — Kevin Julianto
– Kevin Julianto, Commented Nov 3, 2017 at 19:36

UpmostScarab · Accepted Answer · 2017-11-03 19:37:41Z

1

Try using .truncate() , if called after opening file it destroys it's content.

TEXTFILE = open("data.csv", "w")
TEXTFILE.truncate()

for i in book_list:
    TEXTFILE.write("{},{},{},{}".format(i[0],i[1],i[2],i[3]))   

TEXTFILE.close()

I hope I understood you correctly.

edited Nov 3, 2017 at 19:37

answered Nov 3, 2017 at 19:26

UpmostScarab

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6 Comments

Kevin Julianto Over a year ago

I already change the "w" with "w+" but the result still same. but thankyou btw :)

UpmostScarab Over a year ago

@KevinJulianto so did I understood what you are trying to do? You want to overwrite contents?

UpmostScarab Over a year ago

@KevinJulianto please try the new version of my code.

R Nar Over a year ago

@UpmostScarab, w mode should also truncate the file so this shouldnt change anything

Anton vBR Over a year ago

You can write (*i[0:4]) too shorten.

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