ufl team mailing list archive

[Johan Hake <johan.hake@xxxxxxxxx>]

Run this and see whats happens:

def jada(bada=[]):
    bada.append(5)
    return bada

print jada()
print jada()

Johan

On Monday May 2 2011 13:55:53 Anders Logg wrote:
> On Mon, May 02, 2011 at 01:26:58PM +0200, Martin Sandve Alnæs wrote:
> > Declaring default arguments with mutable object like dicts such as
> > this line is dangerous in Python.
> > def compute_form_data(self, object_names={}, common_cell=None,
> > element_mapping={}):
> > If object_names or element_mapping is modified, the
> > modifications change the default object for future calls.
> 
> How do you mean modified? You mean the default will change if a value
> is passed to the function with element_mapping=<something>?
> 
> > Therefore it's a good habit to use None instead:
> > def compute_form_data(self, object_names=None, common_cell=None,
> > 
> > element_mapping=None):
> >     if object_names is None: object_names = {}
> >     if element_mapping is None: element_mapping = {}
> >     ...
> 
> ok.
> 
> --
> Anders
> 
> > On 2 May 2011 10:13,  <noreply@xxxxxxxxxxxxx> wrote:
> > > ------------------------------------------------------------
> > > revno: 1021
> > > committer: Anders Logg <logg@xxxxxxxxx>
> > > branch nick: ufl-main
> > > timestamp: Mon 2011-05-02 10:11:12 +0200
> > > message:
> > >  Initial work on replacement for UFL set_foo functions
> > > modified:
> > >  ufl/algorithms/preprocess.py
> > >  ufl/form.py
> > > 
> > > 
> > > 
> > > Your team UFL Core Team is subscribed to branch lp:ufl.
> > > To unsubscribe from this branch go to
> > > https://code.launchpad.net/~ufl-core/ufl/main/+edit-subscription
> > > 
> > > === modified file 'ufl/algorithms/preprocess.py'
> > > --- ufl/algorithms/preprocess.py        2011-04-26 20:03:38 +0000
> > > +++ ufl/algorithms/preprocess.py        2011-05-02 08:11:12 +0000
> > > @@ -7,7 +7,7 @@
> > >  __license__  = "GNU LGPL version 3 or any later version"
> > >  __date__ = "2009-12-07"
> > > 
> > > -# Last changed: 2011-04-26
> > > +# Last changed: 2011-05-02
> > > 
> > >  from ufl.log import info, debug, warning, error
> > >  from ufl.assertions import ufl_assert
> > > @@ -21,7 +21,7 @@
> > >  from ufl.algorithms.analysis import extract_num_sub_domains,
> > > extract_integral_data, unique_tuple from ufl.algorithms.formdata
> > > import FormData
> > > 
> > > -def preprocess(form, object_names={}, common_cell=None):
> > > +def preprocess(form, object_names={}, common_cell=None,
> > > element_mapping={}): """
> > >     Preprocess raw input form to obtain form metadata, including a
> > >     modified (preprocessed) form more easily manipulated by form
> > > @@ -94,24 +94,8 @@
> > >     form_data.sub_elements        =
> > > extract_sub_elements(form_data.elements) form_data.unique_sub_elements
> > > = unique_tuple(form_data.sub_elements)
> > > 
> > > -    # FIXME: Need to look at logic here, FFC does not support the last
> > > two cases -
> > > -    # Store cell
> > > -    if not common_cell is None:
> > > -        form_data.cell = common_cell
> > > -    elif form_data.elements:
> > > -        cells = [element.cell() for element in form_data.elements]
> > > -        cells = [cell for cell in cells if not cell.domain() is None]
> > > -        if len(cells) == 0:
> > > -            error("Unable to extract form data. Reason: Missing cell
> > > definition in form.") -        form_data.cell = cells[0]
> > > -    elif form._integrals:
> > > -        # Special case to allow functionals only depending on
> > > geometric variables, with no elements -        form_data.cell =
> > > form._integrals[0].integrand().cell() -    else:
> > > -        # Special case to allow integral of constants to pass through
> > > without crashing -        form_data.cell = None
> > > -        warning("Form is empty, no elements or integrals, cell is
> > > undefined.") +    # Store common cell
> > > +    form_data.cell = common_cell
> > > 
> > >     # Store data related to cell
> > >     if form_data.cell is None:
> > > 
> > > === modified file 'ufl/form.py'
> > > --- ufl/form.py 2011-04-26 20:03:38 +0000
> > > +++ ufl/form.py 2011-05-02 08:11:12 +0000
> > > @@ -96,11 +96,11 @@
> > >         "Return form metadata (None if form has not been preprocessed)"
> > >         return self._form_data
> > > 
> > > -    def compute_form_data(self, object_names={}, common_cell=None):
> > > +    def compute_form_data(self, object_names={}, common_cell=None,
> > > element_mapping={}): "Compute and return form metadata"
> > >         if self._form_data is None:
> > >             from ufl.algorithms.preprocess import preprocess
> > > -            self._form_data = preprocess(self, object_names,
> > > common_cell) +            self._form_data = preprocess(self,
> > > object_names, common_cell, element_mapping) return self.form_data()
> > 
> > >     def is_preprocessed(self):
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