DEPR: Series.ptp()
xref #18262
- [x] tests added / passed
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry
# [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21614?src=pr&el=h1) Report
> Merging [#21614](https://codecov.io/gh/pandas-dev/pandas/pull/21614?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/36422a88474396148bd7d5d38aa238ea844d9555?src=pr&el=desc) will **increase** coverage by `0.03%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/21614/graphs/tree.svg?src=pr&width=650&token=eZ4WkYLtcO&height=150)](https://codecov.io/gh/pandas-dev/pandas/pull/21614?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #21614      +/-   ##
==========================================
+ Coverage    91.9%   91.93%   +0.03%     
==========================================
  Files         154      159       +5     
  Lines       49562    49734     +172     
==========================================
+ Hits        45549    45722     +173     
+ Misses       4013     4012       -1
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.31% <100%> (ø)` | :arrow_up: |
| #single | `41.99% <0%> (+0.14%)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/21614?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/generic.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZ2VuZXJpYy5weQ==) | `96.21% <100%> (-0.01%)` | :arrow_down: |
| [pandas/core/indexes/datetimes.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9kYXRldGltZXMucHk=) | `95.45% <0%> (-0.22%)` | :arrow_down: |
| [pandas/core/indexes/timedeltas.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy90aW1lZGVsdGFzLnB5) | `91.05% <0%> (-0.2%)` | :arrow_down: |
| [pandas/core/dtypes/cast.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZHR5cGVzL2Nhc3QucHk=) | `88.36% <0%> (-0.13%)` | :arrow_down: |
| [pandas/core/indexes/accessors.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW5kZXhlcy9hY2Nlc3NvcnMucHk=) | `90.09% <0%> (-0.1%)` | :arrow_down: |
| [pandas/core/internals.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvaW50ZXJuYWxzLnB5) | `95.53% <0%> (-0.07%)` | :arrow_down: |
| [pandas/tseries/offsets.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL3RzZXJpZXMvb2Zmc2V0cy5weQ==) | `97.15% <0%> (-0.02%)` | :arrow_down: |
| [pandas/core/frame.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvZnJhbWUucHk=) | `97.19% <0%> (ø)` | :arrow_up: |
| [pandas/core/arrays/\_\_init\_\_.py](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvYXJyYXlzL19faW5pdF9fLnB5) | `100% <0%> (ø)` | :arrow_up: |
| ... and [31 more](https://codecov.io/gh/pandas-dev/pandas/pull/21614/diff?src=pr&el=tree-more) | |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21614?src=pr&el=continue).
> **Legend** - [Click here to learn more](https://docs.codecov.io/docs/codecov-delta)
> `Δ = absolute <relative> (impact)`, `ø = not affected`, `? = missing data`
> Powered by [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/21614?src=pr&el=footer). Last update [36422a8...cede496](https://codecov.io/gh/pandas-dev/pandas/pull/21614?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Thanks @jorisvandenbossche have moved the docstring to `_make_stat_function` @jreback thanks - done - all green lgtm. @jorisvandenbossche  Just curious why Series.ptp() was deprecated? It was very useful shorthand for finding the period range of a DateTime column.

```python
df.DATE_TIME.ptp()

Timedelta('56 days 01:04:15')
``` sure but it’s just one more method to maintain