Adding a new line to a file in Python

Question

So I have a file that is in this format (no, this is not what the file looks exactly like)

aaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbb
ccccccccccccccccccc
ddddddddddddddddddd

I want to append a new line to the file so that it looks like

aaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbb
ccccccccccccccccccc
ddddddddddddddddddd
eeeeeeeeeeeeeeeeeee

but whenever I use

with open(filename, "a") as updatedFile:
    nextLine="\n%s" % (lineToAdd)
    updatedFile.write(nextLine)

I get

aaaaaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbbbbb
ccccccccccccccccccc
ddddddddddddddddddd

eeeeeeeeeeeeeeeeeee

How would I go about fixing this?

Martijn Pieters · Accepted Answer · 2013-12-04 23:22:51Z

5

You have a file that already had a newline at the end:

aaaaaaaaaaaaaaaaaaa\n
bbbbbbbbbbbbbbbbbbb\n
ccccccccccccccccccc\n
ddddddddddddddddddd\n

and you wrote a newline plus the additional line:

aaaaaaaaaaaaaaaaaaa\n
bbbbbbbbbbbbbbbbbbb\n
ccccccccccccccccccc\n
ddddddddddddddddddd\n
\n
eeeeeeeeeeeeeeeeeee

Write your additional line with the newline at the end:

with open(filename, "a") as updatedFile:
    nextLine="%s\n" % (lineToAdd)
    updatedFile.write(nextLine)

so that you end up with:

aaaaaaaaaaaaaaaaaaa\n
bbbbbbbbbbbbbbbbbbb\n
ccccccccccccccccccc\n
ddddddddddddddddddd\n
eeeeeeeeeeeeeeeeeee\n

answered Dec 4, 2013 at 23:22

Martijn Pieters

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1 Comment

Ah I see the logic now. Thanks so much for the help!