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Source code for galaxy.util.expressions

"""
Expression evaluation support.

For the moment this depends on python's eval. In the future it should be
replaced with a "safe" parser.
"""

from collections import MutableMapping
from itertools import chain


[docs]class ExpressionContext( MutableMapping ):
[docs] def __init__( self, dict, parent=None ): """ Create a new expression context that looks for values in the container object 'dict', and falls back to 'parent' """ self.dict = dict self.parent = parent
def __delitem__(self, key): if key in self.dict: del self.dict[key] elif self.parent is not None and key in self.parent: del self.parent[key] def __iter__(self): return chain(iter(self.dict), iter(self.parent or [])) def __len__(self): return len(self.dict) + len(self.parent or []) def __getitem__( self, key ): if key in self.dict: return self.dict[key] if self.parent is not None and key in self.parent: return self.parent[key] raise KeyError( key ) def __setitem__( self, key, value ): self.dict[key] = value def __contains__( self, key ): if key in self.dict: return True if self.parent is not None and key in self.parent: return True return False def __str__( self ): return str( self.dict ) def __nonzero__( self ): if not self.dict and not self.parent: return False return True