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Bring back the module level 'backend' #6095

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Merged
merged 4 commits into from
Mar 7, 2016
Merged

Bring back the module level 'backend' #6095

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397bfc7
MNT: Bring back the module level 'backend'
ericdill Mar 2, 2016
f118405
MNT: Set the module level `backend` in pylab_setup
ericdill Mar 2, 2016
f142835
MNT: Set the module backend param at the end
ericdill Mar 2, 2016
5a99151
PEP8: Shorten lines that are too long
ericdill Mar 2, 2016
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34 changes: 20 additions & 14 deletions lib/matplotlib/backends/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -8,15 +8,18 @@
import warnings


def pylab_setup(backend=None):
backend = matplotlib.get_backend()


def pylab_setup(name=None):
'''return new_figure_manager, draw_if_interactive and show for pyplot

This provides the backend-specific functions that are used by
pyplot to abstract away the difference between interactive backends.

Parameters
----------
backend : str, optional
name : str, optional
The name of the backend to use. If `None`, falls back to
``matplotlib.get_backend()`` (which return ``rcParams['backend']``)

Expand All @@ -26,23 +29,23 @@ def pylab_setup(backend=None):
The module which contains the backend of choice

new_figure_manager : function
Create a new figure manage (roughly maps to GUI window)
Create a new figure manager (roughly maps to GUI window)

draw_if_interactive : function
Redraw the current figure if pyplot is interactive

show : function
Show (and possible block) any unshown figures.
Show (and possibly block) any unshown figures.

'''
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calling matplotlib.get_backend() in this function was the main point of the PR that broke this. In either case (passed in arg or calling get_backend) the value just needs to be mirrored out to backend. If we only needed to read this value we would not need global as the function would correctly close over it.

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Ok, so if backend is None, use get_backend() and set the module level backend to the result, then keep going with this function?

# Import the requested backend into a generic module object
if backend is None:
backend = matplotlib.get_backend() # validates, to match all_backends

if backend.startswith('module://'):
backend_name = backend[9:]
if name is None:
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I think

global backend
if name is None:
    name = mpl.get_backend()
backend = name

will do the right thing here. It will always defer to an explicitly passed input and then fall back to get_backend which in the end just consults rcparams for the requested backend. Assigning to the variable marked global will change the object that the module-level attribute points at (with out the global it would just bind a local variable).

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Is there any guarantee that name, if not None, is anything sensible that you would want to set to backends.backend? For example, say I do pylab_setup('keyboard'). Obviously that's dumb since keyboard is not a valid mpl backend. How should pylab_setup handle this? I would imagine that you might want to do the global backend; backend=name at the very end right before the return?

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That is a good idea.

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Alright. Done.

# validates, to match all_backends
name = matplotlib.get_backend()
if name.startswith('module://'):
backend_name = name[9:]
else:
backend_name = 'backend_' + backend
backend_name = 'backend_' + name
backend_name = backend_name.lower() # until we banish mixed case
backend_name = 'matplotlib.backends.%s' % backend_name.lower()

Expand All @@ -65,20 +68,23 @@ def do_nothing_show(*args, **kwargs):
Your currently selected backend, '%s' does not support show().
Please select a GUI backend in your matplotlibrc file ('%s')
or with matplotlib.use()""" %
(backend, matplotlib.matplotlib_fname()))
(name, matplotlib.matplotlib_fname()))

def do_nothing(*args, **kwargs):
pass

backend_version = getattr(backend_mod, 'backend_version',
'unknown')
backend_version = getattr(backend_mod, 'backend_version', 'unknown')

show = getattr(backend_mod, 'show', do_nothing_show)

draw_if_interactive = getattr(backend_mod, 'draw_if_interactive',
do_nothing)

matplotlib.verbose.report('backend %s version %s' %
(backend, backend_version))
(name, backend_version))

# need to keep a global reference to the backend for compatibility
# reasons. See https://github.com/matplotlib/matplotlib/issues/6092
global backend
backend = name
return backend_mod, new_figure_manager, draw_if_interactive, show