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#### References to other Issues or PRs
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Fixes #7229 
Fixes #14973 
Fixes #14975 
Referred to PR 10319
#### Brief description of what is fixed or changed
Added relevant scipy.special functions to sympy/sympy/printing/pycode.py
Added use of SciPy printer to lambdify
Added fix so that lambdify automatically uses scipy if available
Added tests to sympy/utilities/tests/test_lambdify.py
Fixed error in sympy/sympy/printing/pycode.py, replacing lgamma with
loggamma in the _not_in_numpy list
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* utilities
  * lambdify uses scipy automatically if available
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Your release notes are in good order.

Here is what the release notes will look like:

• utilities
  • lambdify uses scipy automatically if available (#14992 by @ramvenkat98)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.2.1.

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Update

The release notes on the wiki have been updated.

@asmeurer @bjodah

Hi,

I've added the relevant scipy.special functions, added SciPyPrinter in lambdify and made lambdify default to scipy if available based on the discussion in #7229. Please let me know if this is accurate and what else needs to be done.

Also, in the testing file, one of the functions I added was test_scipy_transl(), similar to test_numpy_transl() which was already there - however, neither of these functions seem to be doing anything because both the numpy and scipy translation dictionaries are empty. Should they still be there?

Thanks!

@asmeurer @bjodah

Hi,

Could you provide some feedback and let me know to proceed further on this pull request?

Thanks

You need to write out "fixes" separately for each issue in the PR description so they will all be automatically closed.

@asmeurer @bjodah

I've updated the pull request according to the reviews:

1. Set numpy.random.seed(0) before the random tests
2. Also adding "numpy" to the modules list in lambdify when scipy is present (and changing the order of Printer selection accordingly to look for SciPy printer before NumPy printer)
3. Wrote out fixes separately for each issue in the PR

However, exactly one Travis test is failing right now and it seems to be a random failure unrelated to the fix - could this test be re-run?

Thanks

Yes, I restarted the test, thank you for telling.

@asmeurer @bjodah

Hi,

are these fixes ok and can the pull request be merged?

Thanks again

@asmeurer @bjodah

Hi,

may I have an update on the status of this pull request? Should I fix anything more or is it ok to be merged? (Sorry for commenting multiple times in a row, I figured it's been a few days since the last activity so I brought it up again).

Thanks

@ramvenkat98 thank you very much for your contribution (and sorry for the wait)

@ramvenkat98
I just tried a simple call on of the Bessel function of the first kind in sympy and tried to lambdify it to scipy's special.jv and it did not work. Is there something that I am missing to invoke the translation from sympy to scipy in the improved lambdfy in sympy1.3

from sympy import *
import scipy.special as SciSpec
#scipy ref 
#https://docs.scipy.org/doc/scipy/reference/generated/scipy.special.jv.html#scipy.special.jv
Order=1; Arg=1.2
SciSpec.jv(Order, Arg)
>>>0.49828905756721553
#sympy call
nu, z=symbols('nu, z')
#https://docs.sympy.org/latest/modules/functions/special.html?highlight=bessel#module-
sympy.functions.special.bessel
b=besselj(nu, z); b
N(b.subs({nu:Order, z:Arg}))
>>>0.498289057567215
bN=lambdify((nu, z), b, dummify=False)
bN(Order, Arg)
>>>NameError                                 Traceback (most recent call last)
<ipython-input-10-3f7a3bb1d5f0> in <module>()
      1 bN=lambdify((nu, z), b, dummify=False)
----> 2 bN(Order, Arg)
~/anaconda3/lib/python3.6/site-packages/numpy/__init__.py in <lambda>(nu, z)
NameError: name 'besselj' is not defined

@GProtoZeroW @asmeurer @bjodah

When using the version of sympy pulled from Github, I don't get this error; however, when using sympy installed as the Anaconda package, I do. Perhaps, this is because this issue has already been fixed on Github but did not make it to the currently released version?

SymPy 1.1.1 is available from the default channel for Anaconda. If you want SymPy >=1.2 you need to install from the conda-forge channel (at least until the default get updated).

@ramvenkat98 I did the Anaconda install I will have to do the github one to test out. And thanks for adding scipy to lambdfiy it's been needed. Just two questions: one does Heaviside from sympy now translate over to numpy's heaviside (https://docs.scipy.org/doc/numpy-1.14.0/reference/generated/numpy.heaviside.html). And two do you have a Ex of using the conversion from a sympy integral to a scipy integral; cause that would be something quite useful

@GProtoZeroW I'm not sure of the answers to those questions - you could ask them on the sympy google group, or make feature requests for them - to my knowledge, Heaviside hasn't been mapped from sympy to numpy but it certainly seems useful.