Partition.find is used (and works) in esp32/modules/flashbdev.py:

bdev = Partition.find(Partition.TYPE_DATA, label='vfs')

I think you need to specify the partition type?

For reference, here is @dpgeorge original comment on the functionality:
#4910 (comment)

To construct a Partition you now either pass in a label, or a constant, like so:
runningpart = Partition(Partition.RUNNING)
fatfs = Partition('fatfs')

Passing just the label also does not work,

>>> Partition('ident')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 2] ENOENT

@jimmo
Yes, passing both parts does work, but it seems that label should just work by itself also, and it does not.

>>> Partition.find(type=0x5A, label='ident')
[<Partition type=90, subtype=0, address=36864, size=24576, label=ident, encrypted=0>]

Seems this is probably an issue with Espressif, since MicroPython just hands off the search to ESP IDF https://docs.espressif.com/projects/esp-idf/en/stable/api-reference/storage/spi_flash.html#_CPPv418esp_partition_find20esp_partition_type_t23esp_partition_subtype_tPKc

As mentioned in #4910 (comment) there are 2 ways to construct a partition object:

1. via constructor, then it accepts an integer constant or string identifier, eg Partition('fatfs')
2. via Partition.find() for more advanced use and full control over the search

Doing Partition('ident') should just work if you have "ident" defined in partitions.csv. Eg Partition('vfs') works on the main firmware.

Here is my partition table:

ident,    0x5A, 0x00,    0x9000,  0x6000
phy_init, data, phy,     0xf000,  0x1000,
factory,  app,  factory, 0x10000, 0x180000,

Note that Partition('factory') works, as well as phy_init, but Partition('ident') does not.

>>> Partition('factory')
<Partition type=0, subtype=0, address=65536, size=1572864, label=factory, encrypted=0>
>>> Partition('phy_init')
<Partition type=1, subtype=1, address=61440, size=4096, label=phy_init, encrypted=0>
>>> Partition('ident')
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
OSError: [Errno 2] ENOENT

But, ident is found by type, as above,

>>> Partition.find(type=0x5A)
[<Partition type=90, subtype=0, address=36864, size=24576, label=ident, encrypted=0>]

The IDF docs does have this one line:
type: Partition type, one of esp_partition_type_t values

For which, esp_partition_type_t values are:
https://docs.espressif.com/projects/esp-idf/en/stable/api-reference/storage/spi_flash.html#_CPPv420esp_partition_type_t

ESP_PARTITION_TYPE_APP = 0x00
Application partition type.

ESP_PARTITION_TYPE_DATA = 0x01
Data partition type.

Perhaps custom partition types are not supported when searching by label.

Further documentation on custom partitions: https://docs.espressif.com/projects/esp-idf/en/stable/api-guides/partition-tables.html#type-field

The boot loader ignores any type other than 0x00 and 0x01. While I was aware of this and found this satisfactory. I didn't expect other features of the partition API to ignore it.

Either way, I no longer think this is a MicroPython bug and I'm happy to close this. Perhaps the documentation could do with a bump. Maybe I should poke Espressif on this.

Perhaps custom partition types are not supported when searching by label.

Right, that's the problem. The IDF doesn't (AFAIK) provide a way to search all partition types for a given identifier. You must know the type to search for it. The MicroPython bindings search both TYPE_APP and TYPE_DATA (in that order) when given a string, and fails if the string is not found under one of those types.

I don't think it's sensible for MicroPython to search all types (eg a for loop over 0x00-0xff).

I guess the point is you can define the same label more than once for different types.

That sounds sensible. Thanks!

Conclusion: You cannot search only by a label if the partition type is not APP or DATA, this is an ESP-IDF limitation. If you're searching for a partition by name and it is not either APP or DATA, then you must also explictly specify the type, eg:

Partition.find(type=0x5A, label='ident')

wont-fix