Grouper use

#1

Hi everybody,

I try to play with "sharex" feature. Then, I have been guided to the
class "Grouper" of module cbook:

http://matplotlib.sourceforge.net/api/cbook_api.html

So I tried the following example:

···

##############################
from matplotlib.cbook import *

g = Grouper()
g.join('a', 'b')
##############################

I obtain:

Traceback (most recent call last):
  File "test_grouper.py", line 4, in <module>
    g.join('a', 'b')
  File ".../matplotlib/cbook.py", line 1118, in join
    set_a = mapping.setdefault(ref(a), [ref(a)])
TypeError: cannot create weak reference to 'str' object

What is the problem?

Thanks in advance,

Julien

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impossible, he is very probably wrong." (first law of AC Clarke)

#2

TP wrote:

Hi everybody,

I try to play with "sharex" feature. Then, I have been guided to the
class "Grouper" of module cbook:

http://matplotlib.sourceforge.net/api/cbook_api.html

So I tried the following example:

##############################
from matplotlib.cbook import *

g = Grouper()
g.join('a', 'b')
##############################

I obtain:

Traceback (most recent call last):
  File "test_grouper.py", line 4, in <module>
    g.join('a', 'b')
  File ".../matplotlib/cbook.py", line 1118, in join
    set_a = mapping.setdefault(ref(a), [ref(a)])
TypeError: cannot create weak reference to 'str' object

What is the problem?

Grouper is implemented using weak references, which are supported only for some types of objects, as described here:
http://docs.python.org/library/weakref.html

Evidently the cbook Grouper docstring was written when the implementation was different, and did not use weakref. So, you have found a major bug in the docstring.

Eric

···

Thanks in advance,

Julien

#3

Yes -- I'll update the docstring. The weakref support was added afterward during one of my many memory leak crusades :wink:

What were you attempting to do with the Grouper? You shouldn't have to use the class directly to use the sharex/sharey functionality -- it's only an implementation detail.

Mike

Eric Firing wrote:

···

TP wrote:
  

Hi everybody,

I try to play with "sharex" feature. Then, I have been guided to the
class "Grouper" of module cbook:

http://matplotlib.sourceforge.net/api/cbook_api.html

So I tried the following example:

##############################
from matplotlib.cbook import *

g = Grouper()
g.join('a', 'b')
##############################

I obtain:

Traceback (most recent call last):
  File "test_grouper.py", line 4, in <module>
    g.join('a', 'b')
  File ".../matplotlib/cbook.py", line 1118, in join
    set_a = mapping.setdefault(ref(a), [ref(a)])
TypeError: cannot create weak reference to 'str' object

What is the problem?
    
Grouper is implemented using weak references, which are supported only for some types of objects, as described here:
http://docs.python.org/library/weakref.html

Evidently the cbook Grouper docstring was written when the implementation was different, and did not use weakref. So, you have found a major bug in the docstring.

Eric

Thanks in advance,

Julien

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