<p dir="auto"><a class="issue-link js-issue-link" data-error-text="Failed to load title" data-id="31164020" data-permission-text="Title is private" data-url="https://github.com/pandas-dev/pandas/issues/6848" data-hovercard-type="pull_request" data-hovercard-url="/pandas-dev/pandas/pull/6848/hovercard" href="https://github.com/pandas-dev/pandas/pull/6848">#6848</a> is no where mentioned in the release notes. There's a single item on <code class="notranslate">.order</code></p>
<p dir="auto">changing to quicksort, but it doesn't explicitly warn that the sort was previously stable<br>
and now isn't. There's also no warning about <code class="notranslate">series.sort</code> changing as well.<br>
That API has been around forever and afaict nothing was gained by breaking it.</p>
<p dir="auto">This was a fairly reckless change in my opinion, I do wish the current maintainers<br>
cared more about backwards-compatibility then they seem to in the latest releases.</p>
<p dir="auto">It seems that drop_duplicates() and duplicated() methods are not working properly for large integer columns. Here is my example data frame <a href="http://pastebin.com/KVHxUpgz" rel="nofollow">http://pastebin.com/KVHxUpgz</a></p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="import pandas as pd

pd.read_clipboard(delimiter=',')
r = x.duplicated(keep=False)
print(x[r])"><pre class="notranslate"><code class="notranslate">import pandas as pd

pd.read_clipboard(delimiter=',')
r = x.duplicated(keep=False)
print(x[r])
</code></pre></div>
<p dir="auto">This gives me:<br>
x1       x2<br>
8   16000010001  8470207<br>
95  16000010009  8470039</p>
<p dir="auto">Clearly these are not duplicates but seems like pandas thinks they are!</p>
<p dir="auto">Also drop_duplicates() seems to fail:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="print(len(x),len(x.drop_duplicates()))"><pre class="notranslate"><code class="notranslate">print(len(x),len(x.drop_duplicates()))
</code></pre></div>
<p dir="auto">gives: 101 100</p>
<p dir="auto">When I convert my columns to string they are not duplicates anymore:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="r1 = x.apply(lambda x: '%d-%d' % tuple(x),axis=1).duplicated()
print(r1.sum())"><pre class="notranslate"><code class="notranslate">r1 = x.apply(lambda x: '%d-%d' % tuple(x),axis=1).duplicated()
print(r1.sum())
</code></pre></div>
<p dir="auto">is 0 as it should.</p>
<p dir="auto">Here is the versions:</p>
<p dir="auto">pd.show_versions()</p>
<h2 dir="auto">INSTALLED VERSIONS</h2>
<p dir="auto">commit: None<br>
python: 3.4.3.final.0<br>
python-bits: 64<br>
OS: Windows<br>
OS-release: 7<br>
machine: AMD64<br>
processor: Intel64 Family 6 Model 42 Stepping 7, GenuineIntel<br>
byteorder: little<br>
LC_ALL: None<br>
LANG: fi_FI</p>
<p dir="auto">pandas: 0.17.0<br>
nose: None<br>
pip: 7.1.2<br>
setuptools: 18.4<br>
Cython: 0.23.4<br>
numpy: 1.10.1<br>
scipy: 0.16.0<br>
statsmodels: None<br>
IPython: 4.0.0<br>
sphinx: 1.3.1<br>
patsy: 0.4.0<br>
dateutil: 2.4.2<br>
pytz: 2015.6<br>
blosc: None<br>
bottleneck: 1.0.0<br>
tables: 3.2.2<br>
numexpr: 2.4.4<br>
matplotlib: 1.4.3<br>
openpyxl: 2.2.6<br>
xlrd: 0.9.4<br>
xlwt: 1.0.0<br>
xlsxwriter: 0.7.7<br>
lxml: 3.4.4<br>
bs4: 4.4.1<br>
html5lib: 0.999<br>
httplib2: None<br>
apiclient: None<br>
sqlalchemy: 1.0.9<br>
pymysql: None<br>
psycopg2: None</p>