Getting FileNotFoundError when trying to open a file for reading in Python 3

Question

I am using the OS module to open a file for reading, but I'm getting a FileNotFoundError.

I am trying to

find all the files in a given sub-directory that contain the word "mda"
for each of those files, grab the string in the filename just after two "_"s (indicates a specific code called an SIC)
open that file for reading
will write to a master file for some Mapreduce processing later

When I try to do the opening, I get the following error:

 File "parse_mda_SIC.py", line 16, in <module>
     f = open(file, 'r')
FileNotFoundError: [Errno 2] No such file or directory:        
'mda_3357_2017-03-08_1000230_000143774917004005__3357.txt'

I am suspicious the issue is either with the "file" variable or the fact that it is one directory down, but confused why this would occur when I am using OS to address that lower directory.

I have the following code :

working_dir = "data/"

for file in os.listdir(working_dir):
    if (file.find("mda") != -1):
        SIC = re.findall("__(\d+)", file)
        f = open(file, 'r')

I would expect to be able to open the file without issue and then create my list from the data. Thanks for your help.

You probably need to append the directory to the file name in order for it to work. — MyNameIsCaleb, Apr 28 '19 at 23:04
Yes, it is getting the file name only at the start of your code but not keeping the entire directory. — MyNameIsCaleb, Apr 28 '19 at 23:07

MyNameIsCaleb · Accepted Answer · 2019-04-28T23:11:05.187

2

This should work for you. You need to append the directory because it sees it as just the file name at the top of your code and will look only in the directory where your code is located for that file name.

for file in os.listdir(working_dir):
    if (file.find("mda") != -1):
        SIC = re.findall("__(\d+)", file)
        f = open(os.path.join(working_dir, file), 'r')

Also it's a good practice to open files using a context manager of with as it will handle closing your file when it is no longer needed:

for file in os.listdir(working_dir):
    if (file.find("mda") != -1):
        SIC = re.findall("__(\d+)", file)
        with open(os.path.join(working_dir, file), 'r') as f:
            # do stuff with f here

edited Apr 28 '19 at 23:11

answered Apr 28 '19 at 23:07

MyNameIsCaleb

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No problem, I just edited also to suggest using a context manager. If this answered your question please hit the check mark. :) – MyNameIsCaleb Apr 28 '19 at 23:11
I usually do, but it's telling me I need to wait 5 mins before accepting – Vaslo Apr 28 '19 at 23:12
Ah gotcha, no issues, whenever it allows. – MyNameIsCaleb Apr 28 '19 at 23:14

score 0 · Answer 2 · edited Apr 28 '19 at 23:18

0

You need to append the directory, like this:

f = open(os.path.join(working_dir, file, 'r'))

edited Apr 28 '19 at 23:18

Samuel

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answered Apr 28 '19 at 23:12

fames

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Getting FileNotFoundError when trying to open a file for reading in Python 3

2 Answers2