|
|
# -*- coding: utf-8 -*-
|
|
|
"""Mimic C structs with lots of extra functionality.
|
|
|
"""
|
|
|
|
|
|
#*****************************************************************************
|
|
|
# Copyright (C) 2001-2004 Fernando Perez <fperez@colorado.edu>
|
|
|
#
|
|
|
# Distributed under the terms of the BSD License. The full license is in
|
|
|
# the file COPYING, distributed as part of this software.
|
|
|
#*****************************************************************************
|
|
|
|
|
|
__all__ = ['Struct']
|
|
|
|
|
|
import types
|
|
|
import pprint
|
|
|
|
|
|
from IPython.genutils import list2dict2
|
|
|
|
|
|
class Struct:
|
|
|
"""Class to mimic C structs but also provide convenient dictionary-like
|
|
|
functionality.
|
|
|
|
|
|
Instances can be initialized with a dictionary, a list of key=value pairs
|
|
|
or both. If both are present, the dictionary must come first.
|
|
|
|
|
|
Because Python classes provide direct assignment to their members, it's
|
|
|
easy to overwrite normal methods (S.copy = 1 would destroy access to
|
|
|
S.copy()). For this reason, all builtin method names are protected and
|
|
|
can't be assigned to. An attempt to do s.copy=1 or s['copy']=1 will raise
|
|
|
a KeyError exception. If you really want to, you can bypass this
|
|
|
protection by directly assigning to __dict__: s.__dict__['copy']=1 will
|
|
|
still work. Doing this will break functionality, though. As in most of
|
|
|
Python, namespace protection is weakly enforced, so feel free to shoot
|
|
|
yourself if you really want to.
|
|
|
|
|
|
Note that this class uses more memory and is *much* slower than a regular
|
|
|
dictionary, so be careful in situations where memory or performance are
|
|
|
critical. But for day to day use it should behave fine. It is particularly
|
|
|
convenient for storing configuration data in programs.
|
|
|
|
|
|
+,+=,- and -= are implemented. +/+= do merges (non-destructive updates),
|
|
|
-/-= remove keys from the original. See the method descripitions.
|
|
|
|
|
|
This class allows a quick access syntax: both s.key and s['key'] are
|
|
|
valid. This syntax has a limitation: each 'key' has to be explicitly
|
|
|
accessed by its original name. The normal s.key syntax doesn't provide
|
|
|
access to the keys via variables whose values evaluate to the desired
|
|
|
keys. An example should clarify this:
|
|
|
|
|
|
Define a dictionary and initialize both with dict and k=v pairs:
|
|
|
>>> d={'a':1,'b':2}
|
|
|
>>> s=Struct(d,hi=10,ho=20)
|
|
|
|
|
|
The return of __repr__ can be used to create a new instance:
|
|
|
>>> s
|
|
|
Struct({'__allownew': True, 'a': 1, 'b': 2, 'hi': 10, 'ho': 20})
|
|
|
|
|
|
Note: the special '__allownew' key is used for internal purposes.
|
|
|
|
|
|
__str__ (called by print) shows it's not quite a regular dictionary:
|
|
|
>>> print s
|
|
|
Struct({'__allownew': True, 'a': 1, 'b': 2, 'hi': 10, 'ho': 20})
|
|
|
|
|
|
Access by explicitly named key with dot notation:
|
|
|
>>> s.a
|
|
|
1
|
|
|
|
|
|
Or like a dictionary:
|
|
|
>>> s['a']
|
|
|
1
|
|
|
|
|
|
If you want a variable to hold the key value, only dictionary access works:
|
|
|
>>> key='hi'
|
|
|
>>> s.key
|
|
|
Traceback (most recent call last):
|
|
|
File "<stdin>", line 1, in ?
|
|
|
AttributeError: Struct instance has no attribute 'key'
|
|
|
|
|
|
>>> s[key]
|
|
|
10
|
|
|
|
|
|
Another limitation of the s.key syntax (and Struct(key=val)
|
|
|
initialization): keys can't be numbers. But numeric keys can be used and
|
|
|
accessed using the dictionary syntax. Again, an example:
|
|
|
|
|
|
This doesn't work (prompt changed to avoid confusing the test system):
|
|
|
->> s=Struct(4='hi')
|
|
|
Traceback (most recent call last):
|
|
|
...
|
|
|
SyntaxError: keyword can't be an expression
|
|
|
|
|
|
But this does:
|
|
|
>>> s=Struct()
|
|
|
>>> s[4]='hi'
|
|
|
>>> s
|
|
|
Struct({4: 'hi', '__allownew': True})
|
|
|
>>> s[4]
|
|
|
'hi'
|
|
|
"""
|
|
|
|
|
|
# Attributes to which __setitem__ and __setattr__ will block access.
|
|
|
# Note: much of this will be moot in Python 2.2 and will be done in a much
|
|
|
# cleaner way.
|
|
|
__protected = ('copy dict dictcopy get has_attr has_key items keys '
|
|
|
'merge popitem setdefault update values '
|
|
|
'__make_dict __dict_invert ').split()
|
|
|
|
|
|
def __init__(self,dict=None,**kw):
|
|
|
"""Initialize with a dictionary, another Struct, or by giving
|
|
|
explicitly the list of attributes.
|
|
|
|
|
|
Both can be used, but the dictionary must come first:
|
|
|
Struct(dict), Struct(k1=v1,k2=v2) or Struct(dict,k1=v1,k2=v2).
|
|
|
"""
|
|
|
self.__dict__['__allownew'] = True
|
|
|
if dict is None:
|
|
|
dict = {}
|
|
|
if isinstance(dict,Struct):
|
|
|
dict = dict.dict()
|
|
|
elif dict and type(dict) is not types.DictType:
|
|
|
raise TypeError,\
|
|
|
'Initialize with a dictionary or key=val pairs.'
|
|
|
dict.update(kw)
|
|
|
# do the updating by hand to guarantee that we go through the
|
|
|
# safety-checked __setitem__
|
|
|
for k,v in dict.items():
|
|
|
self[k] = v
|
|
|
|
|
|
|
|
|
def __setitem__(self,key,value):
|
|
|
"""Used when struct[key] = val calls are made."""
|
|
|
if key in Struct.__protected:
|
|
|
raise KeyError,'Key '+`key`+' is a protected key of class Struct.'
|
|
|
if not self['__allownew'] and key not in self.__dict__:
|
|
|
raise KeyError(
|
|
|
"Can't create unknown attribute %s - Check for typos, or use allow_new_attr to create new attributes!" %
|
|
|
key)
|
|
|
|
|
|
self.__dict__[key] = value
|
|
|
|
|
|
def __setattr__(self, key, value):
|
|
|
"""Used when struct.key = val calls are made."""
|
|
|
self.__setitem__(key,value)
|
|
|
|
|
|
def __str__(self):
|
|
|
"""Gets called by print."""
|
|
|
|
|
|
return 'Struct('+ pprint.pformat(self.__dict__)+')'
|
|
|
|
|
|
def __repr__(self):
|
|
|
"""Gets called by repr.
|
|
|
|
|
|
A Struct can be recreated with S_new=eval(repr(S_old))."""
|
|
|
return self.__str__()
|
|
|
|
|
|
def __getitem__(self,key):
|
|
|
"""Allows struct[key] access."""
|
|
|
return self.__dict__[key]
|
|
|
|
|
|
def __contains__(self,key):
|
|
|
"""Allows use of the 'in' operator.
|
|
|
|
|
|
Examples:
|
|
|
>>> s = Struct(x=1)
|
|
|
>>> 'x' in s
|
|
|
True
|
|
|
>>> 'y' in s
|
|
|
False
|
|
|
>>> s[4] = None
|
|
|
>>> 4 in s
|
|
|
True
|
|
|
>>> s.z = None
|
|
|
>>> 'z' in s
|
|
|
True
|
|
|
"""
|
|
|
return key in self.__dict__
|
|
|
|
|
|
def __iadd__(self,other):
|
|
|
"""S += S2 is a shorthand for S.merge(S2)."""
|
|
|
self.merge(other)
|
|
|
return self
|
|
|
|
|
|
def __add__(self,other):
|
|
|
"""S + S2 -> New Struct made form S and S.merge(S2)"""
|
|
|
Sout = self.copy()
|
|
|
Sout.merge(other)
|
|
|
return Sout
|
|
|
|
|
|
def __sub__(self,other):
|
|
|
"""Return S1-S2, where all keys in S2 have been deleted (if present)
|
|
|
from S1."""
|
|
|
Sout = self.copy()
|
|
|
Sout -= other
|
|
|
return Sout
|
|
|
|
|
|
def __isub__(self,other):
|
|
|
"""Do in place S = S - S2, meaning all keys in S2 have been deleted
|
|
|
(if present) from S1."""
|
|
|
|
|
|
for k in other.keys():
|
|
|
if self.has_key(k):
|
|
|
del self.__dict__[k]
|
|
|
|
|
|
def __make_dict(self,__loc_data__,**kw):
|
|
|
"Helper function for update and merge. Return a dict from data."
|
|
|
|
|
|
if __loc_data__ == None:
|
|
|
dict = {}
|
|
|
elif type(__loc_data__) is types.DictType:
|
|
|
dict = __loc_data__
|
|
|
elif isinstance(__loc_data__,Struct):
|
|
|
dict = __loc_data__.__dict__
|
|
|
else:
|
|
|
raise TypeError, 'Update with a dict, a Struct or key=val pairs.'
|
|
|
if kw:
|
|
|
dict.update(kw)
|
|
|
return dict
|
|
|
|
|
|
def __dict_invert(self,dict):
|
|
|
"""Helper function for merge. Takes a dictionary whose values are
|
|
|
lists and returns a dict. with the elements of each list as keys and
|
|
|
the original keys as values."""
|
|
|
|
|
|
outdict = {}
|
|
|
for k,lst in dict.items():
|
|
|
if type(lst) is types.StringType:
|
|
|
lst = lst.split()
|
|
|
for entry in lst:
|
|
|
outdict[entry] = k
|
|
|
return outdict
|
|
|
|
|
|
def clear(self):
|
|
|
"""Clear all attributes."""
|
|
|
self.__dict__.clear()
|
|
|
|
|
|
def copy(self):
|
|
|
"""Return a (shallow) copy of a Struct."""
|
|
|
return Struct(self.__dict__.copy())
|
|
|
|
|
|
def dict(self):
|
|
|
"""Return the Struct's dictionary."""
|
|
|
return self.__dict__
|
|
|
|
|
|
def dictcopy(self):
|
|
|
"""Return a (shallow) copy of the Struct's dictionary."""
|
|
|
return self.__dict__.copy()
|
|
|
|
|
|
def popitem(self):
|
|
|
"""S.popitem() -> (k, v), remove and return some (key, value) pair as
|
|
|
a 2-tuple; but raise KeyError if S is empty."""
|
|
|
return self.__dict__.popitem()
|
|
|
|
|
|
def update(self,__loc_data__=None,**kw):
|
|
|
"""Update (merge) with data from another Struct or from a dictionary.
|
|
|
Optionally, one or more key=value pairs can be given at the end for
|
|
|
direct update."""
|
|
|
|
|
|
# The funny name __loc_data__ is to prevent a common variable name
|
|
|
# which could be a fieled of a Struct to collide with this
|
|
|
# parameter. The problem would arise if the function is called with a
|
|
|
# keyword with this same name that a user means to add as a Struct
|
|
|
# field.
|
|
|
newdict = Struct.__make_dict(self,__loc_data__,**kw)
|
|
|
for k,v in newdict.iteritems():
|
|
|
self[k] = v
|
|
|
|
|
|
def merge(self,__loc_data__=None,__conflict_solve=None,**kw):
|
|
|
"""S.merge(data,conflict,k=v1,k=v2,...) -> merge data and k=v into S.
|
|
|
|
|
|
This is similar to update(), but much more flexible. First, a dict is
|
|
|
made from data+key=value pairs. When merging this dict with the Struct
|
|
|
S, the optional dictionary 'conflict' is used to decide what to do.
|
|
|
|
|
|
If conflict is not given, the default behavior is to preserve any keys
|
|
|
with their current value (the opposite of the update method's
|
|
|
behavior).
|
|
|
|
|
|
conflict is a dictionary of binary functions which will be used to
|
|
|
solve key conflicts. It must have the following structure:
|
|
|
|
|
|
conflict == { fn1 : [Skey1,Skey2,...], fn2 : [Skey3], etc }
|
|
|
|
|
|
Values must be lists or whitespace separated strings which are
|
|
|
automatically converted to lists of strings by calling string.split().
|
|
|
|
|
|
Each key of conflict is a function which defines a policy for
|
|
|
resolving conflicts when merging with the input data. Each fn must be
|
|
|
a binary function which returns the desired outcome for a key
|
|
|
conflict. These functions will be called as fn(old,new).
|
|
|
|
|
|
An example is probably in order. Suppose you are merging the struct S
|
|
|
with a dict D and the following conflict policy dict:
|
|
|
|
|
|
S.merge(D,{fn1:['a','b',4], fn2:'key_c key_d'})
|
|
|
|
|
|
If the key 'a' is found in both S and D, the merge method will call:
|
|
|
|
|
|
S['a'] = fn1(S['a'],D['a'])
|
|
|
|
|
|
As a convenience, merge() provides five (the most commonly needed)
|
|
|
pre-defined policies: preserve, update, add, add_flip and add_s. The
|
|
|
easiest explanation is their implementation:
|
|
|
|
|
|
preserve = lambda old,new: old
|
|
|
update = lambda old,new: new
|
|
|
add = lambda old,new: old + new
|
|
|
add_flip = lambda old,new: new + old # note change of order!
|
|
|
add_s = lambda old,new: old + ' ' + new # only works for strings!
|
|
|
|
|
|
You can use those four words (as strings) as keys in conflict instead
|
|
|
of defining them as functions, and the merge method will substitute
|
|
|
the appropriate functions for you. That is, the call
|
|
|
|
|
|
S.merge(D,{'preserve':'a b c','add':[4,5,'d'],my_function:[6]})
|
|
|
|
|
|
will automatically substitute the functions preserve and add for the
|
|
|
names 'preserve' and 'add' before making any function calls.
|
|
|
|
|
|
For more complicated conflict resolution policies, you still need to
|
|
|
construct your own functions. """
|
|
|
|
|
|
data_dict = Struct.__make_dict(self,__loc_data__,**kw)
|
|
|
|
|
|
# policies for conflict resolution: two argument functions which return
|
|
|
# the value that will go in the new struct
|
|
|
preserve = lambda old,new: old
|
|
|
update = lambda old,new: new
|
|
|
add = lambda old,new: old + new
|
|
|
add_flip = lambda old,new: new + old # note change of order!
|
|
|
add_s = lambda old,new: old + ' ' + new
|
|
|
|
|
|
# default policy is to keep current keys when there's a conflict
|
|
|
conflict_solve = list2dict2(self.keys(),default = preserve)
|
|
|
|
|
|
# the conflict_solve dictionary is given by the user 'inverted': we
|
|
|
# need a name-function mapping, it comes as a function -> names
|
|
|
# dict. Make a local copy (b/c we'll make changes), replace user
|
|
|
# strings for the three builtin policies and invert it.
|
|
|
if __conflict_solve:
|
|
|
inv_conflict_solve_user = __conflict_solve.copy()
|
|
|
for name, func in [('preserve',preserve), ('update',update),
|
|
|
('add',add), ('add_flip',add_flip),
|
|
|
('add_s',add_s)]:
|
|
|
if name in inv_conflict_solve_user.keys():
|
|
|
inv_conflict_solve_user[func] = inv_conflict_solve_user[name]
|
|
|
del inv_conflict_solve_user[name]
|
|
|
conflict_solve.update(Struct.__dict_invert(self,inv_conflict_solve_user))
|
|
|
#print 'merge. conflict_solve: '; pprint(conflict_solve) # dbg
|
|
|
#print '*'*50,'in merger. conflict_solver:'; pprint(conflict_solve)
|
|
|
for key in data_dict:
|
|
|
if key not in self:
|
|
|
self[key] = data_dict[key]
|
|
|
else:
|
|
|
self[key] = conflict_solve[key](self[key],data_dict[key])
|
|
|
|
|
|
def has_key(self,key):
|
|
|
"""Like has_key() dictionary method."""
|
|
|
return self.__dict__.has_key(key)
|
|
|
|
|
|
def hasattr(self,key):
|
|
|
"""hasattr function available as a method.
|
|
|
|
|
|
Implemented like has_key, to make sure that all available keys in the
|
|
|
internal dictionary of the Struct appear also as attributes (even
|
|
|
numeric keys)."""
|
|
|
return self.__dict__.has_key(key)
|
|
|
|
|
|
def items(self):
|
|
|
"""Return the items in the Struct's dictionary, in the same format
|
|
|
as a call to {}.items()."""
|
|
|
return self.__dict__.items()
|
|
|
|
|
|
def keys(self):
|
|
|
"""Return the keys in the Struct's dictionary, in the same format
|
|
|
as a call to {}.keys()."""
|
|
|
return self.__dict__.keys()
|
|
|
|
|
|
def values(self,keys=None):
|
|
|
"""Return the values in the Struct's dictionary, in the same format
|
|
|
as a call to {}.values().
|
|
|
|
|
|
Can be called with an optional argument keys, which must be a list or
|
|
|
tuple of keys. In this case it returns only the values corresponding
|
|
|
to those keys (allowing a form of 'slicing' for Structs)."""
|
|
|
if not keys:
|
|
|
return self.__dict__.values()
|
|
|
else:
|
|
|
ret=[]
|
|
|
for k in keys:
|
|
|
ret.append(self[k])
|
|
|
return ret
|
|
|
|
|
|
def get(self,attr,val=None):
|
|
|
"""S.get(k[,d]) -> S[k] if k in S, else d. d defaults to None."""
|
|
|
try:
|
|
|
return self[attr]
|
|
|
except KeyError:
|
|
|
return val
|
|
|
|
|
|
def setdefault(self,attr,val=None):
|
|
|
"""S.setdefault(k[,d]) -> S.get(k,d), also set S[k]=d if k not in S"""
|
|
|
if not self.has_key(attr):
|
|
|
self[attr] = val
|
|
|
return self.get(attr,val)
|
|
|
|
|
|
def allow_new_attr(self, allow = True):
|
|
|
""" Set whether new attributes can be created inside struct
|
|
|
|
|
|
This can be used to catch typos by verifying that the attribute user
|
|
|
tries to change already exists in this Struct.
|
|
|
"""
|
|
|
self['__allownew'] = allow
|
|
|
|
|
|
|
|
|
# end class Struct
|
|
|
|
|
|
|
