Convenience facilities related to Python functions.

Short summary:

• akw: A trite class to store positional and keyword arguments.

• callif: Call func(*a,**kw) if doit is true otherwise just print it out.

• callmethod_if: Call the named method on the object obj if it exists.

• derived_from: A property which must be recomputed if the revision of another property exceeds the snapshot revision.

• derived_property: A property which must be recomputed if the reference revision (attached to self) exceeds the snapshot revision.

• func_a_kw: Return a string representing a call to func(*a,**kw).

• func_a_kw_fmt: Prepare a percent-format string and associated argument list describing a call to func(*a,**kw). Return format,args.

• funccite: Return a citation for a function (name and code location).

• funcname: Return a name for the supplied function func. Several objects do not have a name attribute, such as partials.

• prop: A substitute for the builtin @property.

Functions

callif(doit, func, *a, **kw)

Call func(*a,**kw) if doit is true otherwise just print it out.

The parameter func may be preceeded optionally by a dict containing modes. The current modes are:

• 'print': the print function, default the builtin print

callmethod_if(obj, method, default=None, a=None, kw=None)

Call the named method on the object obj if it exists.

If it does not exist, return default (which defaults to None). Otherwise call getattr(obj, method)(*a, **kw). a defaults to (). kw defaults to {}.

derived_from(property_name)

A property which must be recomputed if the revision of another property exceeds the snapshot revision.

derived_property(func, original_revision_name='_revision', lock_name='_lock', property_name=None, unset_object=None)

A property which must be recomputed if the reference revision (attached to self) exceeds the snapshot revision.

func_a_kw(func, *a, **kw)

Return a string representing a call to func(*a,**kw).

func_a_kw_fmt(func, *a, **kw)

Prepare a percent-format string and associated argument list describing a call to func(*a,**kw). Return format,args.

The func argument can also be a string, typically a prepared description of func such as funccite(func).

Note: the returned args is a list for easy incorporation into further arguments. The % operator requires a tuple.

funccite(func)

Return a citation for a function (name and code location).

funcname(func)

Return a name for the supplied function func. Several objects do not have a name attribute, such as partials.

prop(func)

A substitute for the builtin @property.

The builtin @property decorator lets internal AttributeErrors escape. While that can support properties that appear to exist conditionally, in practice this is almost never what I want, and it masks deeper errors. Hence this wrapper for @property that transmutes internal AttributeErrors into RuntimeErrors.

Classes

class akw

A trite class to store positional and keyword arguments.

It's a constant annoyance to me that there no neat way to store a pairing of positional and keyword arguments for use with a function. You can eaily store a sequence, a mapping, and you can store a function with arguments using functools.partial.

Example:

>>> args = akw(1, 2, x=3, z=4)
>>> args
akw(*(1, 2),**{'x': 3, 'z': 4})
>>> args.args
(1, 2)
>>> args.kwargs
{'x': 3, 'z': 4}
>>> import sys
>>> prakw=akw(1, 2, file=sys.stdout)
>>> prakw(print, 3)
1 2 3

akw.__call__(self, func, *cargs, **ckwargs)

Call func with self.args and cargs as positional arguments and self.kwargs and ckwargs as keyword arguments.