BUG: pd.period_range ignores multiple of start frequency.

[jaheba]

Fixes: #47465

• closes BUG: pd.period_range ignores multiple of start frequency #47465
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[phofl]

Looks like this broke stuff

[jaheba]

Hopefully that is fixed now.

@phofl However, during testing I found this behaviour odd:

In [1]: import pandas as pd

In [2]: p = pd.Period("2020", freq="Y")

In [3]: pd.Period(p, freq="3Y")
Out[3]: Period('2020', 'A-DEC')

In [4]: pd.Period(p, freq="3D")
Out[4]: Period('2020-12-31', '3D')

The freq argument is ignored when the value is already a Period and has the same base-freq. I assume this is also not intended?

[jaheba]

This looks wrong:

pandas/pandas/_libs/tslibs/period.pyx

Lines 2554 to 2561 in d9dd128

	elif is_period_object(value):
	other = value
	if freq is None or freq._period_dtype_code == other.freq._period_dtype_code:
	ordinal = other.ordinal
	freq = other.freq
	else:
	converted = other.asfreq(freq)
	ordinal = converted.ordinal

Checking the _period_dtype_code should not be sufficient, if the .n do not match.

[phofl]

This might be deliberate, are there tests covering this?

[jaheba]

This might be deliberate, are there tests covering this?

I would be very surprised by this, so let's see: #47613

[github-actions]

This pull request is stale because it has been open for thirty days with no activity. Please update and respond to this comment if you're still interested in working on this.

[mroeschke]

Thanks for the pull request, but it appears to have gone stale. If interested in continuing, please merge in the main branch, address any review comments and/or failing tests, and we can reopen.