Pattern Matching between two lists - Python

Question

i have a bunch of zip files in a directory and would like to get notified if one of them is missing .

Example code:

a = ['pattern1.zip', 'pattern2.zip', 'pattern3.zip']
b = []
for root,dirs,files in os.walk(some_path):
    for i in files:
        if i.endswith(('pattern1.zip', 'pattern2.zip', 'pattern3.zip')):
            b.append(i)

Output: b = ['test-pattern1.zip', 'test-pattern2.zip', 'test-pattern3.zip']

would like to match the contents of 'b' with 'a' and check if any of the zip files are missing

if any(i.endswith(x) for x in a)

Ma0
– Ma0

2018-05-04 09:42:34 +00:00
Commented May 4, 2018 at 9:42 — Ma0
– Ma0, Commented May 4, 2018 at 9:42
Make sets of a and b and look for the set difference.

BoarGules
– BoarGules

2018-05-04 09:43:51 +00:00
Commented May 4, 2018 at 9:43 — BoarGules
– BoarGules, Commented May 4, 2018 at 9:43
is it always in the format test-patternX.zip?

Ashish Acharya
– Ashish Acharya

2018-05-04 09:52:43 +00:00
Commented May 4, 2018 at 9:52 — Ashish Acharya
– Ashish Acharya, Commented May 4, 2018 at 9:52

Alex Hall · Accepted Answer · 2018-05-04 09:56:03Z

3

I would take a different approach:

patterns = {'pattern1.zip', 'pattern2.zip', 'pattern3.zip'}
for root, dirs, files in os.walk(some_path):
    for f in files:
        for pattern in patterns:
            if f.endswith(pattern):
                patterns.remove(pattern)
                break

print('Missing patterns:', patterns)

answered May 4, 2018 at 9:56

Alex Hall

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4 Comments

sourabh vs Over a year ago

Works like a charm , Thanks a lot

sourabh vs Over a year ago

for some strange reason it stopped working . If i rename the file (pattern1.zip) to 'patter.zip' , it is not able to detect the change and if the file with 'pattern1.zip' is deleted it is not able to detect that the file is missing . Any thoughts ? @Alex Hall

sourabh vs Over a year ago

Also , if there are multiple subdirectories with similar files matching the patterns ,the script is not able to iterate over them

Alex Hall Over a year ago

Read ericlippert.com/2014/03/05/how-to-debug-small-programs, try to figure it out, and if you get stuck, ask a new question on SO with a minimal reproducible example that demonstrates only one of these problems as precisely as possible. But my first thought is that you have multiple files ending with the same pattern in different subdirectories, and if the program sees at least one it will mark the pattern as not missing, even if others have been removed, renamed, or aren't in some of the subdirectories.

Simon · Accepted Answer · 2018-05-04 09:56:46Z

3

You can convert the lists to sets and take their difference 1:

files_that_should_be_present = ['pattern1.zip', 'pattern2.zip', 'pattern3.zip']
files_that_are_present = ['pattern1.zip', 'pattern2.zip']

files_missing = list(set(files_that_should_be_present) - set(files_that_are_present))
print(files_missing)

Outputs: ['pattern3.zip']

answered May 4, 2018 at 9:56

Simon

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1 Comment

Alex Hall Over a year ago

The filenames don't match exactly, it's based on endswith.

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