API: Deprecate Categorical fastpath argument

[TomAugspurger]

After #16015 the fastpath argument to the Categorical constructor is unnecessary since you can skip the categorical validation by passing in a CategoricalDtype.l

[kaichogami]

Hi, I would like to work on this.

[TomAugspurger]

Cool. The argument is [here]( https://github.com/pandas-dev/pandas/blob/7e159aeec1d5d2e79311ca688c0e594f0fd5f709/pandas/core/categorical.py#L245). You'll want to warn when it's used, and tell people to use a CategoricalDtype. The trickier part will be finding all the places the argument is currently used, and pass or construct an instance of a `CategoricalDtype` there instead.

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On Thu, Oct 12, 2017 at 2:08 AM, Asish Panda ***@***.***> wrote: Hi, I would like to work on this. — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#17562 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/ABQHIiQwSO7R03Cv9xpBjHPBzHw87Wbaks5srbrSgaJpZM4PaMOS> .

[jreback]

closing in favor of #20110