keep x rows and delete all from csv file

I want to be able to specify how many rows I want to keep and delete the rest, also preserving the header.

I found some code which let’s you delete the first 5 rows but how can I make it do what I want?

with open ('myfile.csv', 'wb') as outfile:
    outfile.writelines(data_in[1])
    outfile.writelines(data_in[5:])

For example if I have this CSV

6.5, 5.4, 0, 000
6.5, 5.4, 1, 610
1.2, 4.0, 0, 530
3.2, 5.4, 1, 330
4.2, 3.0, 0, 320
5.5, 2.3, 1, 780
1.3, 4.4, 0, 520
5.3, 1.0, 0, 420

I just want to specify a number to my script… let’s say (2) and it will KEEP 2 rows and remove all others

output would become:

6.5, 5.4, 0, 000
6.5, 5.4, 1, 610

Can i also make it save it with a different name?

Answer

If you first read your original CSV-file into variable data_in with commands

with open('my_original_file.csv') as inp:
     data_in = inp.readlines()

you may continue:

n = int(input("How many rows after header you want to write: "))

with open('myfile.csv', 'w') as outfile:
    outfile.writelines(data_in[:n+1])

This will write

• the header row — data_in[0], and
• subsequent n rows — data_in[1] to data_in[n]