Floor and ceil methods during pandas.eval which are provided by numexpr
- [x] closes #24353
- [x] passes `git diff upstream/master -u -- "*.py" | flake8 --diff`
- [x] whatsnew entry

Hello @anjsudh! Thanks for updating the PR.







Cheers ! There are no PEP8 issues in this Pull Request. :beers: 

##### Comment last updated on December 25, 2018 at 18:06 Hours UTC # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=h1) Report
> Merging [#24355](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/14c33b0e531ba955ae20a6e37750261133e5391e?src=pr&el=desc) will **not change** coverage.
> The diff coverage is `n/a`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24355/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=tree)

```diff
@@           Coverage Diff           @@
##           master   #24355   +/-   ##
=======================================
  Coverage   92.29%   92.29%           
=======================================
  Files         162      162           
  Lines       51808    51808           
=======================================
  Hits        47817    47817           
  Misses       3991     3991
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.7% <ø> (ø)` | :arrow_up: |
| #single | `42.99% <ø> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24355/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.6% <ø> (ø)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24355?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/24355?src=pr&el=footer). Last update [14c33b0...6abf412](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 # [Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=h1) Report
> Merging [#24355](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=desc) into [master](https://codecov.io/gh/pandas-dev/pandas/commit/1ebfd8a9fda12cd68c3e068b777c7a0a2470dfaf?src=pr&el=desc) will **increase** coverage by `<.01%`.
> The diff coverage is `100%`.

[![Impacted file tree graph](https://codecov.io/gh/pandas-dev/pandas/pull/24355/graphs/tree.svg?width=650&token=eZ4WkYLtcO&height=150&src=pr)](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=tree)

```diff
@@            Coverage Diff             @@
##           master   #24355      +/-   ##
==========================================
+ Coverage   92.31%   92.31%   +<.01%     
==========================================
  Files         166      166              
  Lines       52412    52416       +4     
==========================================
+ Hits        48382    48386       +4     
  Misses       4030     4030
```

| Flag | Coverage Δ | |
|---|---|---|
| #multiple | `90.73% <100%> (ø)` | :arrow_up: |
| #single | `43.06% <66.66%> (ø)` | :arrow_up: |

| [Impacted Files](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=tree) | Coverage Δ | |
|---|---|---|
| [pandas/core/computation/check.py](https://codecov.io/gh/pandas-dev/pandas/pull/24355/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vY2hlY2sucHk=) | `92.3% <100%> (+1.39%)` | :arrow_up: |
| [pandas/core/computation/ops.py](https://codecov.io/gh/pandas-dev/pandas/pull/24355/diff?src=pr&el=tree#diff-cGFuZGFzL2NvcmUvY29tcHV0YXRpb24vb3BzLnB5) | `95.63% <100%> (+0.03%)` | :arrow_up: |

------

[Continue to review full report at Codecov](https://codecov.io/gh/pandas-dev/pandas/pull/24355?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/24355?src=pr&el=footer). Last update [1ebfd8a...3ccb40c](https://codecov.io/gh/pandas-dev/pandas/pull/24355?src=pr&el=lastupdated). Read the [comment docs](https://docs.codecov.io/docs/pull-request-comments).
 Getting an error: "err: pandas should not import: numexpr". I haven't imported numexpr in my diff. The error resolves when I don't import _NUMEXPR_INSTALLED and _NUMEXPR_VERSION. Any ideas on how to go about the version check without the import?

Also, is there a reason for us to check that numexpr is not imported? The import is anyways in a try catch block

Any inputs would help here? lgtm. ping on green. you have a lint error: https://dev.azure.com/pandas-dev/pandas/_build/results?buildId=5788 can you merge master and update @jreback Hope you can have a look? thanks @anjsudh 

yeah this was a bit tricky because of our delayed import of numexpr :>