Python writing to the wrong directory

Question

For some reason, my python code is writing to the wrong directory.

I'm setting the output directory I want to write to here:

output_dir = os.path.join('..', '..', 'output_files', 'aws_instance_list', 'csv')

And I'm setting the file name here:

output_file = output_dir + 'aws-instance-master-list-' + today + '.csv'

But when I write the file out, I get a file in this location with this name:

..\..output_files\aws_instance_list\csvaws-instance-master-list-11-19-2019.csv

Instead, I want the file to be called:

..\..output_files\aws_instance_list\csv\aws-instance-master-list-11-19-2019.csv

What am I doing wrong?

output_file = output_dir + 'aws-instance-master-list-' + today + '.csv' did you print out output dir? You should be able to spot what's wrong. This is also why make sure you keep constructing all paths using os.path.join or pathlib. — Paritosh Singh
– Paritosh Singh, Commented Nov 19, 2019 at 16:39
@ParitoshSingh definitely second pathlib. Path(output_dir) / f'aws-instance-master-list-{today}.csv') reads very well — FHTMitchell
– FHTMitchell, Commented Nov 19, 2019 at 16:44

nepdavis · Accepted Answer · 2019-11-19 16:45:41Z

1

os.path.join doesn't join a "\" to the end. Try this:

output_dir = os.path.join('..', '..', 'output_files', 'aws_instance_list', 'csv', '') # add '' to the end 

output_file = output_dir + 'aws-instance-master-list-' + today + '.csv'

Adding the '' to the end of os.path.join will add an ending "\", which will separate your csv subdirectory and the filename.

answered Nov 19, 2019 at 16:45

nepdavis

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2 Comments

gelonida Over a year ago

This works, but you should not use + for joining a directory and a path. output_file = os.path.join(output_dir. 'aws-instance-master-list-' + today + '.csv') would be the better option. In this case you could also remove , '' from the line aboce.

nepdavis Over a year ago

I totally agree, was just keeping it as close as possible to op's code

Seljuk Gulcan · Accepted Answer · 2019-11-19 16:49:21Z

0

from doc of join method:

The return value is the concatenation of path and any members of *paths with exactly one directory separator (os.sep) following each non-empty part except the last, meaning that the result will only end in a separator if the last part is empty.

This means output_dir's last character is not / or \.

You may add it like:

output_file = output_dir + '\\aws-instance-master-list-' + today + '.csv' (Note the escape character, also see @gelonida's comment on why this is dangerous and you should avoid using it)

or better way is:

output_file = os.path.join(output_dir, 'aws-instance-master-list-' + today + '.csv')

The last one is better because you don't need to deal with operating system dependent path naming conventions.

edited Nov 19, 2019 at 16:49

answered Nov 19, 2019 at 16:46

Seljuk Gulcan

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2 Comments

gelonida Over a year ago

do not use '\\' for joining paths. As far as I know this will fail on linux. '/' on the other hand works on both platforms. But the real answer is to never use '+' to join path strings. just use os.path.join()

gelonida Over a year ago

alternatively use os.path.sep, which will be "\\" or "/" respectively

gelonida · Accepted Answer · 2019-11-22 11:40:12Z

0

output_file = os.path.join(
    output_dir, 'aws-instance-master-list-' + today + '.csv')

As @Paritosh Singh mentioned. Never use + to construct file paths.

edited Nov 22, 2019 at 11:40

answered Nov 19, 2019 at 16:45

gelonida

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