Clean way to get the "true" stem of a Path object?

Question

Expected inputs and outputs:

a                 -> a
a.txt             -> a
archive.tar.gz    -> archive
directory/file    -> file
d.x.y.z/f.a.b.c   -> f
logs/date.log.txt -> date # Mine!

Here's my implementation that feels dirty to me:

>>> from pathlib import Path
>>> example_path = Path("August 08 2015, 01'37'30.log.txt")
>>> example_path.stem
"August 08 2015, 01'37'30.log"
>>> example_path.suffixes
['.log', '.txt']
>>> suffixes_length = sum(map(len, example_path.suffixes))
>>> true_stem = example_path.name[:-suffixes_length]
>>> true_stem
"August 08 2015, 01'37'30"

Because it breaks on Paths without suffixes:

>>> ns_path = Path("no_suffix")
>>> sl = sum(map(len, ns_path.suffixes))
>>> ns_path.name[:-sl]
''

So I need to check if the Path has a suffix first:

>>> def get_true_stem(path: Path):
...     if path.suffix:
...         sl = sum(map(len, path.suffixes))
...         return path.name[:-sl]
...     else:
...         return path.stem
...
>>>
>>> get_true_stem(example_path)
"August 08, 2015, 01'37'30"
>>> get_true_stem(ns_path)
"no_suffix"

And this is my current use case:

>>> file_date = datetime.strptime(true_stem, "%B %d %Y, %H'%M'%S")
>>> file_date
datetime.datetime(2015, 8, 8, 1, 37, 30)
>>> new_dest = format(file_date, "%Y-%m-%dT%H:%M:%S%z") + ".log" # ISO-8601
>>> shutil.move(str(example_path), new_dest)

Thanks.

It's frustating as `Path` actually knows about these suffixes — they are present in its `suffixes` member. — P-Gn, Feb 18 '20 at 13:28

score 25 · Accepted Answer · edited Sep 11 '19 at 19:09

25

You could just .split it:

>>> Path('logs/date.log.txt').stem.split('.')[0]
'date'

os.path works just as well:

>>> os.path.basename('logs/date.log.txt').split('.')[0]
'date'

It passes all of the tests:

In [11]: all(Path(k).stem.split('.')[0] == v for k, v in {
   ....:     'a': 'a',
   ....:     'a.txt': 'a',
   ....:     'archive.tar.gz': 'archive',
   ....:     'directory/file': 'file',
   ....:     'd.x.y.z/f.a.b.c': 'f',
   ....:     'logs/date.log.txt': 'date'
   ....: }.items())
Out[11]: True

edited Sep 11 '19 at 19:09

Cristian Ciupitu

19,240
7
48
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answered Aug 08 '15 at 06:35

Blender

275,078
51
420
480

[`.partition`](https://docs.python.org/3/library/stdtypes.html#str.partition) could also be used, e.g. `Path('logs/date.log.txt').stem.partition('.')[0]` or `os.path.basename('logs/date.log.txt').partition('.')[0]`. It might even be [faster for some use cases](https://stackoverflow.com/q/47898526/12892). – Cristian Ciupitu Sep 11 '19 at 19:16
1

Note that this does not work for hidden files: `Path('logs/.date.log.txt').stem.split('.')[0] == ''` – pabouk - Ukraine stay strong Nov 17 '21 at 13:58

score 6 · Answer 2 · answered Aug 08 '15 at 06:35

How about a while loop method, where you keep taking .stem until the path has no suffixes remaining , Example -

from pathlib import Path
example_path = Path("August 08 2015, 01'37'30.log.txt")
example_path_stem = example_path.stem
while example_path.suffixes:
    example_path_stem = example_path.stem
    example_path = Path(example_path_stem)

Please note, the while loop exits the loop when example_path.suffixes returns an empty list (As empty list are False like in boolean context) .

Example/Demo -

>>> from pathlib import Path
>>> example_path = Path("August 08 2015, 01'37'30.log.txt")
>>> example_path_stem = example_path.stem
>>> while example_path.suffixes:
...     example_path_stem = example_path.stem
...     example_path = Path(example_path_stem)
...
>>> example_path_stem
"August 08 2015, 01'37'30"

For your second input - no_suffix -

>>> example_path = Path("no_suffix")
>>> example_path_stem = example_path.stem
>>> while example_path.suffixes:
...     example_path_stem = example_path.stem
...     example_path = Path(example_path_stem)
...
>>> example_path_stem
'no_suffix'

score 4 · Answer 3 · answered Apr 04 '20 at 16:05

Here's another possible solution to the given problem:

from pathlib import Path

if __name__ == '__main__':
    dataset = [
        ('a', 'a'),
        ('a.txt', 'a'),
        ('archive.tar.gz', 'archive'),
        ('directory/file', 'file'),
        ('d.x.y.z/f.a.b.c', 'f'),
        ('logs/date.log.txt', 'date'),
    ]
    for path, stem in dataset:
        path = Path(path)
        assert path.name.replace("".join(path.suffixes), "") == stem

score 2 · Answer 4 · answered Jun 30 '21 at 09:18

2

Why not go recursively?

from pathlib import Path

def true_stem(path):
   stem = Path(path).stem
   return stem if stem == path else true_stem(stem)

assert(true_stem('d.x.y.z/f.a.b.c') == 'f')

answered Jun 30 '21 at 09:18

plankthom

61
5

score 1 · Answer 5 · edited Jul 26 '21 at 14:27

1

If you wanted to use pathlib uniquely, you could also use:

>>> Path('logs/date.log.txt').with_suffix('').stem
'date'

EDIT:

As pointed out in the comments this doesn't work if you have an extension with more than 2 suffixes. Although this doesn't sound very likely (and pathlib itself doesn't have a native way to deal with it), if you wanted to use pathlib uniquely, you could use:

>>> Path('logs/date.log.txt.foo').with_suffix('').with_suffix('').stem
'date'

edited Jul 26 '21 at 14:27

buhtz

8,057
11
59
115

answered Jul 18 '20 at 19:09

universvm

153
1
8

1

Doesn't work if there are more than two suffixes: `Path('logs/date.log.txt.foo').with_suffix("").stem` = `'date.log'` – Mandera Sep 23 '20 at 15:19
You are correct. You'd have to add another `.with_suffix("")` which may make it clunky: ` >>> Path('logs/date.log.txt.foo').with_suffix("").with_suffix("").stem 'date' ` – universvm Sep 23 '20 at 16:24

score 1 · Answer 6 · answered Feb 17 '21 at 18:10

Another approach uses pattern matching:

import re
from pathlib import Path
all(re.search('[.]|',Path(k).name) for k,v in {
   'a': 'a',
   'a.txt': 'a',
   'archive.tar.gz': 'archive',
   'directory/file': 'file',
   'd.x.y.z/f.a.b.c': 'f',
   'logs/date.log.txt': 'date'
   }.items())

the pattern '[.]' may be used if all your paths have at least one suffix

Clean way to get the "true" stem of a Path object?

6 Answers6

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