matplotlib-devel Mailing List for matplotlib

I think this first one is sufficient and should work correctly for more things than the second.  I'll go ahead and add this to matplotlib master -- I'm a little wary of changing this in 1.0.x in case someone is relying on the currently broken behavior.

Mike

try: iter(obj)
except TypeError: return False
return True

________________________________________
From: Jason Grout [jas...@cr...]
Sent: Tuesday, March 22, 2011 11:27 PM
To: mat...@li...
Subject: [matplotlib-devel] matplotlib.cbook.iterable

The function matplotlib.cbook.iterable has the documentation:

def iterable(obj):
     'return true if *obj* is iterable'
     try: len(obj)
     except: return False
     return True


However, in Sage, we have some objects that have __len__ defined, but
are not iterable (i.e., they don't implement the iterator protocol).
This is causing us problems when we try to plot some things that use
this function, and matplotlib falsely assumes that the things are
iterable.  After checking around online, it seems that it is safer to
check for iterability by doing something like:

try: iter(obj)
except TypeError: return False
return True

or

import collections
return isinstance(obj, collections.Iterable) # only works for new-style
classes

Or maybe even combining these would be better (though it might be really
redundant and slow, after looking at the code in collections.Iterable...):

try: iter(obj)
except TypeError:
     import collections
     return isinstance(obj, collections.Iterable)
return True

You guys are the python experts, though.  What do you think?

Thanks,

Jason

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Hi,

In my code I have yet another version:

def is_iterable(x):
    """Checks if object is iterable (but not a string)."""
    return hasattr(x, '__iter__')

I specifically wanted to test for lists, tuples and numpy arrays, but
not strings. Depending on the semantics of underscored methods could
be considered flaky coding, though :-)

Ludwig

The function matplotlib.cbook.iterable has the documentation:

def iterable(obj):
     'return true if *obj* is iterable'
     try: len(obj)
     except: return False
     return True


However, in Sage, we have some objects that have __len__ defined, but 
are not iterable (i.e., they don't implement the iterator protocol). 
This is causing us problems when we try to plot some things that use 
this function, and matplotlib falsely assumes that the things are 
iterable.  After checking around online, it seems that it is safer to 
check for iterability by doing something like:

try: iter(obj)
except TypeError: return False
return True

or

import collections
return isinstance(obj, collections.Iterable) # only works for new-style 
classes

Or maybe even combining these would be better (though it might be really 
redundant and slow, after looking at the code in collections.Iterable...):

try: iter(obj)
except TypeError:
     import collections
     return isinstance(obj, collections.Iterable)
return True

You guys are the python experts, though.  What do you think?

Thanks,

Jason