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Incorporating commit: e6acca646abcaaac7515da9b964d5b5291264142

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Bernard 2020-11-11 11:20:29 +01:00
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docs/html/user_guide.rst
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@ -1337,7 +1337,7 @@ candidate can take a lot of time. (The amount of time depends on the
package size, the number of versions pip must try, and other concerns.)
How does backtracking work?
~~~~~~~~~~~~~~~~~~~~~~~~~~~
^^^^^^^^^^^^^^^^^^^^^^^^^^^
When doing a pip install, pip starts by making assumptions about the
packages it needs to install. During the install process it needs to check these
@ -1384,8 +1384,6 @@ version of a package is a good candidate to install. It reduces the risk that
installing a new package will accidentally break an existing installed package,
and so reduces the risk that your environment gets messed up.
Please address this.
What does this behaviour look like?
-----------------------------------
@ -1439,14 +1437,13 @@ Right now backtracking behaviour looks like this:
Downloading cup-3.13.0-py2.py3-none-any.whl (374 kB)
In the above sample output, pip had to download multiple versions of
package cup - cup-3.22.0 to cup-3.13.0 - to find a version that will be
compatible with the other packages - ``spoon``, ``hot-water``, ``cup``
etc.
package ``cup`` - cup-3.22.0 to cup-3.13.0 - to find a version that will be
compatible with the other packages - ``spoon``, ``hot-water``, etc.
These multiple ``Downloading cup-version`` lines show pip backtracking.
Possible ways to reduce backtracking occurring
---------------------------------------------
----------------------------------------------
It's important to mention backtracking behaviour is expected during a
``pip install`` process. What pip is trying to do is complicated - it is
@ -1459,7 +1456,7 @@ here are a number of ways.
.. _1-allow-pip-to-complete-its-backtracking:
1. Allow pip to complete its backtracking
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
In most cases, pip will complete the backtracking process successfully.
It is possible this could take a very long time to complete - this may
@ -1474,7 +1471,7 @@ If you'd prefer not to wait, you can interrupt pip (ctrl and c) and use
.. _2-reduce-the-versions-of-the-backtracking-package:
2. Reduce the number of versions pip will try to backtrack through
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
If pip is backtracking more than you'd like, the next option is to
constrain the number of package versions it tries.
@ -1496,7 +1493,7 @@ can be trial and error.
.. _3-use-constraint-files-or-lockfiles:
3. Use constraint files or lockfiles
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
This option is a progression of 2 above. It requires users to know how
to inspect:
@ -1518,7 +1515,7 @@ suitable constraints file.
.. _4-be-more-strict-on-package-dependencies-during-development:
4. Be more strict on package dependencies during development
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
For package maintainers during the development, give pip some help by
creating constraint files for the dependency tree. This will reduce the