Fixed bug. Added in check for ufunc and evaluates inner expression be…
…fore evaluating outer expression

- [x] closes  #24670 
- [x] passes `black pandas`

Hello @SurajH1! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:





There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2020-05-16 00:21:35 UTC Is this ready to be accepted @maintainters @jbrockmendel  any suggestions on why the failures are only occurring on some systems? @jreback  I tested this branch locally using a function that makes multiple arguments, and it isn't working properly either. It isn't parsing the multiple arguments correctly. 

```python
import pandas as pd
from  numpy import *

print(pd.__version__)

r = pd.eval("floor(1+5)")
print(r)

r = pd.eval("minimum(1 + 5, 4)")  # This one fails
print(r)
``` > any suggestions on why the failures are only occurring on some systems? @jreback

Looking at the Azure CI output logs, it looks like you are failing on the environments that are testing the minimum versions, in particular, the lowest version of `numexpr`. There seems to be an `if` branch that specifically tries to handle the `floor` function. You could try written the test with a different function that isn't `floor`, or fix the if statement causing this error. (`pandas/core/computation/ops.py:602: ValueError`)

The Travis CI failures look like they are on environments that have `numba` installed. Here I am totally guessing, but I imagine that the failing operations use the `eval` capability somewhere internally, and that your changes are causing them to now fail.  can you merge master and get this passing and will have a look closing as stale, if you'd like continue, pls ping.