In-place upgrade from python 3.6 to 3.7

Based on reports Python Bytes and from [here] and [there] it seems like 3.7 is generally faster than 3.6. So, I decided to try it. On one machine, I set up a fresh conda environment with 3.7 and installed all the packages I typically use. The first time I did that, which was months ago, not everything was working, and I put this upgrade plan on hold. Later, I re-tested, and all my packages seemed to be playing nicely with 3.7. I worked in that environment for a while with no problems.

During down time today, I thought it might be good to move another machine to 3.7. This time I decided to take the leap and move my base environment to python 3.7 from 3.6.6. Why not?

There is one step:
$ conda install python=3.7

This takes some time for conda to "solve" the environment. I'm not sure what this actually does, but since it checks for dependencies, it is no wonder that it will take a while because essentially every installed package will need to be removed and reinstalled.

One potential gotcha with this approach is that anything that was pip installed will need to be reinstalled. I think there are a couple of these, but I don't know how to tell which are which. Oh well, I guess I'll find out when something breaks. 

Eventually the environment does get solved, and a plan is constructed. Answer 'y' and conda dutifully downloads and extracts many packages.

Conda does all the work:
Preparing transaction step happens with the spinning slash, and finishes.
Verification step happens with the spinning slash, and finishes.
Removing some deprecated stuff (jupyter js widgets) ...  And then enabling notebook extensions and validating. Give the OK.
Prints done, returns the prompt.

Did it work?

$which python
/Users/brianpm/anaconda3/bin/python

$python --version
Python 3.7.1

$python
Python 3.7.1 | packaged by conda-forge | (default, Nov 13 2018, 09:50:42)
[Clang 9.0.0 (clang-900.0.37)] :: Anaconda custom (64-bit) on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> print(2.**8)
256.0
>>> import numpy as np
>>> import pandas as pd
>>> import matplotlib as mpl
>>> import xarray as xr
>>> xr.DataArray(np.random.randn(2, 3))

array([[-0.355778,  0.836539,  0.210377],
       [ 0.480935,  0.469618, -0.101545]])
Dimensions without coordinates: dim_0, dim_1
>>> data = xr.DataArray(np.random.randn(2, 3), coords={'x': ['a', 'b']}, dims=('x', 'y'))
>>> xr.DataArray(pd.Series(range(3), index=list('abc'), name='foo'))

array([0, 1, 2])
Coordinates:
  * dim_0    (dim_0) object 'a' 'b' 'c'

Okay, this seems to be working. Repeated similar interactive test with ipython. So far, so good.

Lesson: conda is kind of amazing.