CODEWITHSUNDEEP
pythonpython-3.xlistdir
Liam
Liam

Reputation: 23

Python os.listdir is not giving consistent output

I am using Python 3.6.2 in a Conda virtual environment, on Linux Ubuntu 18.04.

I have tried several ways to list both the files and directories of a particular path but I every method I try seems to only list the files in a directory, not the files and directories.

My code contains

directory_contents = os.listdir(run_directory)
print(directory_contents)

which shows only

['170224-ARC122-1-uM-Cis-S1-subsample_R1_001.fastq.gz', '170224-ARC122-1-uM-Cis-S1-subsample_R2_001.fastq.gz']

If I call a break before the listdir command, and then step through the listdir command the variable is filled with the correct contents 

ipdb.set_trace()
print(directory_contents)
directory_contents = os.listdir(run_directory)
print(directory_contents)

*** NameError: name 'directory_contents' is not defined

['170224-ARC122-1-uM-Cis-S1-subsample_R1_001.fastq.gz', 'bw', 'Stats', 'bwChrM', 'bg', '170224-ARC122-1-uM-Cis-S1-subsample_R2_001.fastq.gz', 'bgChrM', 'Log']

Calling the break after the listdir command 

directory_contents = os.listdir(run_directory)
ipdb.set_trace()
print(directory_contents)

gives

['170313-ARC122-no-Cis-S5-subsample_R2_001.fastq.gz', '170313-ARC122-no-Cis-S5-subsample_R1_001.fastq.gz']

What is it that I am not understanding or what extra keyword/argument have I overlooked ? Why am I getting different results depending on if I break before the command or afterwards?

The apparent simplicity of this seems hardly worth posing as a question but I have run out of solutions.

Upvotes: 1

Views: 1229

Answers (1)

Patrick Artner
Patrick Artner

Reputation: 51643

You could use the first result of os.walk():

import os

# demo structure: 5 dirs, 5 files
for n in range(5):
    os.mkdir(f"dir_{n}")

for n in range (10,15):
    with open(f"file_{n}.txt","w") as f:
        f.write("...")

# query
akt_dir, subdirs, files = next(os.walk("./")) # get the first result of the generator
print(akt_dir)
print(subdirs)
print(files)

Output:

./
['dir_0', 'dir_2', 'dir_3', 'dir_4', 'dir_1']
['file_14.txt', 'file_10.txt', 'file_12.txt', 'main.py', 'file_13.txt', 'file_11.txt']

os.walk() returns a generator - so it might query more then you want.

Upvotes: 1

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