Standard imports (#4401)

* Standardize pytest imports

* Standardize numpy/scipy imports

* Document import style

* Fix

* More

* Fix matplotlib imports

* Revert changes to tests

* Motivate import policy

Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>

* Fix missed imports

* Standard np.testing use

Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>

1 files changed, 16 insertions, 0 deletions

diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 31dbf844..70ed6d47 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -246,6 +246,22 @@ Guidelines
    import pandas as pd 
    import networkx as nx
 
+  After importing `sp`` for ``scipy``::
+
+   import scipy as sp
+
+  use the following imports:: 
+ 
+   import scipy.linalg  # call as sp.linalg
+   import scipy.sparse  # call as sp.sparse
+   import scipy.sparse.linalg  # call as sp.sparse.linalg
+   import scipy.stats  # call as sp.stats
+   import scipy.optimize  # call as sp.optimize
+
+  For example, many libraries have a ``linalg`` subpackage: ``nx.linalg``,
+  ``np.linalg``, ``sp.linalg``, ``sp.sparse.linalg``. The above import
+  pattern makes the origin of any particular instance of ``linalg`` explicit.
+
 * Use the decorator ``not_implemented_for`` in ``networkx/utils/decorators.py``
   to designate that a function doesn't accept 'directed', 'undirected',
   'multigraph' or 'graph'.  The first argument of the decorated function should