gh-131236: allow to generate multiple UUIDs at once via CLI by simon04 · Pull Request #131218 · python/cpython

simon04 · 2025-03-14T06:16:08Z

Fixes #131236.

Add --count to the main() of the uuid module.

Sometimes you need more than one UUID. In order to print 42 UUIDs, run python -m uuid --count 42

Inspired by https://www.man7.org/linux/man-pages/man1/uuidgen.1.html

📚 Documentation preview 📚: https://cpython-previews--131218.org.readthedocs.build/

Issue: Allow to generate multiple UUIDs at once via CLI #131236

Sometimes you need more than one UUID. Inspired by https://www.man7.org/linux/man-pages/man1/uuidgen.1.html

donbarbos · 2025-03-14T08:18:49Z

Thank you for idea, but we usually open issue before adding any feature.

Contribution process is documented here: https://devguide.python.org/

hugovk · 2025-03-14T10:41:06Z

Lib/uuid.py

                        help="The name used as part of generating the uuid. "
                        "Only required for uuid3/uuid5 functions.")
+    parser.add_argument("--count", type=int, default=1,
+                        help="Generate more uuids in loop. ")


Suggested change

help="Generate more uuids in loop. ")

help="Generate COUNT UUIDs. Default: 1.")

Or add formatter_class=argparse.ArgumentDefaultsHelpFormatter to argparse.ArgumentParser() and:

Suggested change

help="Generate more uuids in loop. ")

help="Generate this many UUIDs.")

And also delete "By default uuid4 function is used."

I would like to have a short option -C as well so to mimick uuidgen, and use NUM as a metavar instead of COUNT. In addition, we can just say Generate NUM fresh UUIDs

And also delete "By default uuid4 function is used."

Isn't it the default though?

Yes, but argparse.ArgumentDefaultsHelpFormatter prints the default for us:

❯ ./python.exe -m uuid -h usage: python.exe -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8}] [-n NAMESPACE] [-N NAME] [--count COUNT] Generates a uuid using the selected uuid function. options: -h, --help show this help message and exit -u, --uuid {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8} The function to use to generate the uuid. By default uuid4 function is used. (default: uuid4) -n, --namespace NAMESPACE The namespace is a UUID, or '@ns' where 'ns' is a well-known predefined UUID addressed by namespace name. Such as @dns, @url, @oid, and @x500. Only required for uuid3/uuid5 functions. (default: None) -N, --name NAME The name used as part of generating the uuid. Only required for uuid3/uuid5 functions. (default: None) --count COUNT Generate more uuids in loop. (default: 1)

(I have an idea to add colour to those in future.)

Oh. I thought that the suggestion was separate, my bad

With ArgumentDefaultsHelpFormatter it would look the following:

It seems that the typesetting of the help text mixed – Do we start the help text with a capital letter? Do we use a period at the end (this looks strange with the (default: 1) generated by ArgumentDefaultsHelpFormatter)?

> python -m uuid -h usage: python -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8}] [-n NAMESPACE] [-N NAME] [-C NUM] Generates a uuid using the selected uuid function. options: -h, --help show this help message and exit -u, --uuid {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8} The function to use to generate the uuid. (default: uuid4) -n, --namespace NAMESPACE The namespace is a UUID, or '@ns' where 'ns' is a well-known predefined UUID addressed by namespace name. Such as @dns, @url, @oid, and @x500. Only required for uuid3/uuid5 functions. (default: None) -N, --name NAME The name used as part of generating the uuid. Only required for uuid3/uuid5 functions. (default: None) -C, --count NUM Generate NUM fresh UUIDs. (default: 1)

Adding ArgumentDefaultsHelpFormatter, going for lowercase first letter, removing period at the end, adding metavar="NS" for namespace yields a more compact and consistent help output:

> python -m uuid -h usage: python -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8}] [-n NS] [-N NAME] [-C NUM] Generate a UUID using the selected UUID function. options: -h, --help show this help message and exit -u, --uuid {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8} function to generate the UUID (default: uuid4) -n, --namespace NS a UUID, or '@ns' where 'ns' is a well-known predefined UUID addressed by namespace name, such as @dns, @url, @oid, and @x500 (only required for uuid3/uuid5) (default: None) -N, --name NAME name used as part of generating the UUID (only required for uuid3/uuid5) (default: None) -C, --count NUM generate NUM fresh UUIDs (default: 1)

I'm still not happy with the verbose --namespace help, though:

-n, --namespace NS a UUID, or '@ns' where 'ns' is a well-known predefined UUID addressed by namespace name, such as @dns, @url, @oid, and @x500 (only required for uuid3/uuid5) (default: None)

Is the following any better?

-n, --namespace NS a UUID, or @dns, @url, @oid, @x500, or any '@ns' where 'ns' is a well-known predefined UUID addressed by namespace name (only required for uuid3/uuid5) (default: None)

Or specify the few choices explicitly?

-n, --namespace {any UUID,@dns,@url,@oid,@x500} a UUID, or a well-known predefined UUID addressed by namespace name (only required for uuid3/uuid5) (default: None)

Adding ArgumentDefaultsHelpFormatter, going for lowercase first letter, removing period at the end, adding metavar="NS" for namespace yields a more compact and consistent help output:

👍

I'm still not happy with the very verbose "a UUID, or '@ns' where 'ns' is a well-known predefined UUID addressed by namespace name, such as @dns, @url, @oid, and @x500 (only required for uuid3/uuid5)", though. Is "a UUID, or @dns, @url, @oid, @x500, or any '@ns' where 'ns' is a well-known predefined UUID addressed by namespace name (only required for uuid3/uuid5)" any better?

It's a bit better, and I don't have a much better suggestion :)

I think we could also prefix and shorten the "(only required for uuid3/uuid5)" bits, so if you're not using uuid3/5 you can immediately skip it and save some mental effort:

-n, --namespace NS uuid3/uuid5 only: [etc] (default: None) -N, --name NAME uuid3/uuid5 only: name used as part of generating the UUID (default: None)

For --namespace, maybe specify the few choices explicitly?

-n, --namespace {any UUID,@dns,@url,@oid,@x500} uuid3/uuid5 only: a UUID, or a well-known predefined UUID addressed by namespace name (default: None)

Thanks for your ideas. Here's the concise result:

> python -m uuid -h usage: python -m uuid [-h] [-u {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8}] [-n {any UUID,@dns,@url,@oid,@x500}] [-N NAME] [-C NUM] Generate a UUID using the selected UUID function. options: -h, --help show this help message and exit -u, --uuid {uuid1,uuid3,uuid4,uuid5,uuid6,uuid7,uuid8} function to generate the UUID (default: uuid4) -n, --namespace {any UUID,@dns,@url,@oid,@x500} uuid3/uuid5 only: a UUID, or a well-known predefined UUID addressed by namespace name) (default: None) -N, --name NAME uuid3/uuid5 only: name used as part of generating the UUID (default: None) -C, --count NUM generate NUM fresh UUIDs (default: 1)

hugovk · 2025-03-14T10:42:04Z

As mentioned, please open an issue, and add a NEWS file.

cc @picnixz

Doc/library/uuid.rst

picnixz · 2025-03-14T10:44:10Z

Lib/uuid.py

                        help="The name used as part of generating the uuid. "
                        "Only required for uuid3/uuid5 functions.")
+    parser.add_argument("--count", type=int, default=1,
+                        help="Generate more uuids in loop. ")


I would like to have a short option -C as well so to mimick uuidgen, and use NUM as a metavar instead of COUNT. In addition, we can just say Generate NUM fresh UUIDs

picnixz · 2025-03-14T10:46:16Z

Lib/uuid.py

                        help="The name used as part of generating the uuid. "
                        "Only required for uuid3/uuid5 functions.")
+    parser.add_argument("--count", type=int, default=1,
+                        help="Generate more uuids in loop. ")


And also delete "By default uuid4 function is used."

Isn't it the default though?

picnixz · 2025-03-14T10:47:43Z

We also need some What's New entry. The uuid module is an old module that didn't have lots of updates these past 10 years so not everyone may remember that the CLI exists. Since we also improved quite significantly this module these past months, it's good to highlight the new features.

simon04 · 2025-03-14T11:24:32Z

Hi all, thank you for the feedback. I've created an issue, created a news entry, updated the help text to "Generate NUM fresh UUIDs.", added -c, added metavar "NUM".

picnixz

Do we have tests for the CLI? if yes, please update them, otherwise let's add them in a follow-up PR.

Doc/library/uuid.rst

Lib/uuid.py

Misc/NEWS.d/next/Library/2025-03-14-12-22-02.gh-issue-131236.HjqFq0.rst

Doc/library/uuid.rst

sobolevn

Sorry, it is not clear for me, what's your use-case. You can already generate any amount of uuids as simple as:

» for i in {1..4} ; do ./python.exe -m uuid ; done
11afb3ee-2e62-4e7f-93d2-e073cd44b093
4ebad66f-a4b2-4f5e-b34a-2bfbdc6db7ac
d8068024-d316-4ccd-bfae-ded9c3f5c504
400a0201-5fe1-4868-895d-9db6d3288e5c

Basically, all shells support loops.

…jqFq0.rst Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

simon04 · 2025-03-14T12:15:35Z

Sorry, it is not clear for me, what's your use-case.

@sobolevn, invoking 100 Python interpreters on Windows via Git Bash (MINGW64) takes 13s when it could complete in 0.102s

MINGW64$ time sh -c 'seq 100 | xargs -i python.exe -m uuid'
real    0m12.974s
user    0m0.090s
sys     0m0.363s

MINGW64$ time python.exe -c 'import uuid
for _ in range(100):
    print(uuid.uuid4())
'
real    0m0.102s
user    0m0.000s
sys     0m0.015s

simon04 · 2025-03-14T12:17:00Z

Do we have tests for the CLI?

@picnixz, thank you for your review. I've added a CLI test test_cli_uuid4_outputted_with_count.

Doc/whatsnew/3.14.rst

Lib/uuid.py

sobolevn · 2025-03-14T12:31:36Z

@simon04 thanks, these numbers make sense to me!

hugovk · 2025-03-14T15:16:38Z

@simon04 Tip: there's usually no need to click the "Update branch" button:

https://devguide.python.org/getting-started/pull-request-lifecycle/#update-branch-button

hugovk

Thanks!

Lib/uuid.py

hugovk

Thank you!

Something else I noticed, but this can be a followup PR. The docs start with:

library reference
"Command-Line Usage"
library "Example"
"Command-Line Example"

Let's restructure (and use sentence case):

library reference
library "Example"
"Command-line usage"
"Command-line example"

…thon#131218) Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

uuid: add --count to main

f2775cb

Sometimes you need more than one UUID. Inspired by https://www.man7.org/linux/man-pages/man1/uuidgen.1.html

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simon04 added 2 commits March 14, 2025 12:22

Add news

ff6dc1c

"Generate NUM fresh UUIDs."

0f95b45

picnixz changed the title ~~uuid: add --count to main~~ gh-131236: allow to generate multiple UUIDs at once via CLI Mar 14, 2025

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Allow to generate multiple UUIDs at once via CLI #131236

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Update Misc/NEWS.d/next/Library/2025-03-14-12-22-02.gh-issue-131236.H…

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…jqFq0.rst Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Update Doc/library/uuid.rst

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"UUID"

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uuid -C

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test_cli_uuid4_outputted_with_count

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Add 3.14 news

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Merge branch 'main' into uuid-count

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"UUID"

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ArgumentDefaultsHelpFormatter

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namespace

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namespace

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namespace

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	help="Generate more uuids in loop. ")
	help="Generate COUNT UUIDs. Default: 1.")

	help="Generate more uuids in loop. ")
	help="Generate this many UUIDs.")

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