TST: loc misbehaves when Period is at start of 3-level MultiIndex

[proost]

If index is MultiIndex and level of 0 is PeriodIndex, loc function raise
exception if all input of loc does not match index values

Background: This bug only happens when MultiIndex's level is 3 and first level index is PeriodIndex. In this situation, if someone access one row using a '.loc' with a miss match key, then would not raise exception.

Someone already change what i try to do parse_time_string function in '_libs.tslibs.parsing'.
in the past,

def parse_time_string(arg, freq=None, dayfirst=None, yearfirst=None):
    if not isinstance(arg, str):
        return arg

What i try to do:

def parse_time_string(arg, freq=None, dayfirst=None, yearfirst=None):
    if not isinstance(arg, str):
        raise TypeError

now in master:

def parse_time_string(arg, freq=None, dayfirst=None, yearfirst=None):
    if not isinstance(arg, str):
        raise TypeError("parse_time_string argument must be str")

Just add tests for issue.

• closes (loc misbehaves when Period is at start of 3-level MultiIndex #20684)
• tests added / passed
• passes black pandas
• passes git diff upstream/master -u -- "*.py" | flake8 --diff
• whatsnew entry

[jbrockmendel]

Can you add tests specific to parse_time_string. That would go in tests.tslibs.test_parsing

[minhoryang]

@jbrockmendel ping?

[jreback]

can you also make sure we have tests for the entire example in the OP (IOW the working cases as well)

[proost]

@jreback could you also check #29038 ?

[jreback]

ok looks fine, if you'd remove the note, otherwise lgtm. ping on green.

[jreback]

thanks @proost

[proost]

@jbrockmendel @jreback
Thank you for your feedback.