<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> Add <code class="notranslate">__inverse__</code> to Index.</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> Change duplicated to return np.array (PR <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="52548801" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/9112" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/9112/hovercard" href="https://github.com/pandas-dev/pandas/pull/9112">#9112</a>)</li>
</ul>
<p dir="auto">Related to <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="39909905" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/7979" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/7979/hovercard" href="https://github.com/pandas-dev/pandas/pull/7979">#7979</a></p>
<p dir="auto">Because <code class="notranslate">Index</code> is no more the subclass of <code class="notranslate">np.array</code>,  <code class="notranslate">Index.duplicated</code> returns <code class="notranslate">Index</code> with <code class="notranslate">dtype=object</code>. And <code class="notranslate">Index</code> don't accepts logical not.</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="idx = pd.Index([1, 2, 1, 3])

idx.duplicated()
# Index([False, False, True, False], dtype='object')

~idx.duplicated()
# TypeError: bad operand type for unary ~: 'Index'"><pre class="notranslate"><code class="notranslate">idx = pd.Index([1, 2, 1, 3])

idx.duplicated()
# Index([False, False, True, False], dtype='object')

~idx.duplicated()
# TypeError: bad operand type for unary ~: 'Index'
</code></pre></div>
<p dir="auto">As a result, it is impossible to drop data which have duplicated index using expression like <code class="notranslate">df[~df.index.duplicated()]</code>. This expression was worked at the timing of <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="39909905" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/7979" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/7979/hovercard" href="https://github.com/pandas-dev/pandas/pull/7979">#7979</a>.</p>
<p dir="auto">Does <code class="notranslate">Index.duplicated</code> should return <code class="notranslate">np.array</code> with <code class="notranslate">dtype=bool</code>? Or <code class="notranslate">Index</code> should accept logical not?</p>
<p dir="auto">after <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="27737098" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/6380" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/6380/hovercard" href="https://github.com/pandas-dev/pandas/pull/6380">#6380</a>, ability to pretty easily move ops over to the mix-in</p>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> <code class="notranslate">date/time</code> (added in <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="27737098" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/6380" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/6380/hovercard" href="https://github.com/pandas-dev/pandas/pull/6380">#6380</a>)</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> more periods ops? <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="20918891" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/5202" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/5202/hovercard" href="https://github.com/pandas-dev/pandas/issues/5202">#5202</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> additional field accessor (<code class="notranslate">is_beg_year</code>), <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="19366462" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/4823" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/4823/hovercard" href="https://github.com/pandas-dev/pandas/pull/4823">#4823</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> validate <code class="notranslate">argmin/max</code>, (PR <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="39349111" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/7904" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/7904/hovercard" href="https://github.com/pandas-dev/pandas/issues/7904">#7904</a>)</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> StringMethods, e.g. <code class="notranslate">str</code> for <code class="notranslate">Index</code> (not for sub-classes though), <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="51834672" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/9068" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/9068/hovercard" href="https://github.com/pandas-dev/pandas/issues/9068">#9068</a></li>
</ul>
<p dir="auto">(this turns out to be quite tricky, as sometimes construction depends on the existence of a <code class="notranslate">tz</code> attribute)</p>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> <code class="notranslate">freq,frestr,inferred_freq</code></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> <code class="notranslate">is_monotonic</code> <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="157767200" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/13336" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/13336/hovercard" href="https://github.com/pandas-dev/pandas/pull/13336">#13336</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> <code class="notranslate">pd.infer_freq()</code>, related <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="27867645" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/6407" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/6407/hovercard" href="https://github.com/pandas-dev/pandas/issues/6407">#6407</a>,<a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="27872946" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/6408" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/6408/hovercard" href="https://github.com/pandas-dev/pandas/pull/6408">#6408</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> <code class="notranslate">is_unique,lexsort_depth,nlevels</code></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> <code class="notranslate">nunique()</code>,<code class="notranslate">unique()</code>,<code class="notranslate">value_counts()</code>, <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="30440590" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/6734" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/6734/hovercard" href="https://github.com/pandas-dev/pandas/pull/6734">#6734</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> <code class="notranslate">factorize()</code> <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="33231411" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/7090" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/7090/hovercard" href="https://github.com/pandas-dev/pandas/pull/7090">#7090</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> <code class="notranslate">get_loc/find</code> <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="18302926" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/4616" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/4616/hovercard" href="https://github.com/pandas-dev/pandas/issues/4616">#4616</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> <code class="notranslate">__invert__</code> <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="49769148" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/8875" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/8875/hovercard" href="https://github.com/pandas-dev/pandas/issues/8875">#8875</a></li>
</ul>
<p dir="auto">These are related in that they are generic.py functions as they have to compute something then set the axis with the result.</p>
<ul class="contains-task-list">
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> <code class="notranslate">normalize</code> <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="22567385" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/5502" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/5502/hovercard" href="https://github.com/pandas-dev/pandas/issues/5502">#5502</a></li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> <code class="notranslate">tz_convert/tz_localize</code> (though this requires a bit of wrapping as they have an axis parm,<br>
but should be possible), see also here: <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="39391827" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/7915" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/7915/hovercard" href="https://github.com/pandas-dev/pandas/pull/7915">#7915</a> (currently implemented only on <code class="notranslate">DatetimeIndex</code>, <code class="notranslate">PeriodIndex</code> has these as not implemented (and delegating from <code class="notranslate">NDFrame</code> is in <code class="notranslate">core/generic</code>)</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox" checked=""> <code class="notranslate">duplicated/drop_duplicates</code> <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="16102603" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/4060" data-hovercard-type="issue" data-hovercard-url="/pandas-dev/pandas/issues/4060/hovercard" href="https://github.com/pandas-dev/pandas/issues/4060">#4060</a>, (PR <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="39909905" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/7979" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/7979/hovercard" href="https://github.com/pandas-dev/pandas/pull/7979">#7979</a>)</li>
<li class="task-list-item"><input type="checkbox" id="" disabled="" class="task-list-item-checkbox"> <code class="notranslate">has_duplicates</code> <a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="51937288" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/9077" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/9077/hovercard" href="https://github.com/pandas-dev/pandas/pull/9077">#9077</a></li>
</ul>