Entry

"Safe" dictionary

Oct 26th, 2006 04:21
alex novo, Nathan Wallace, unknown unknown, Hans Nowak, Snippet 345, Barry A. Warsaw

"""
Packages: basic_datatypes.dictionaries
"""

"""
    GH> This is ugly! Isn't there a better way to fill in just SOME of
    GH> the %(...)s values in a string and leave the rest as is?

Here's what we use in Mailman:
"""

from UserDict import UserDict   # added by PSST

class SafeDict(UserDict):
    """Dictionary which returns a default value for unknown keys.
    """
    def __init__(self, d=None):
        # optional initial dictionary is a Python 1.5.2-ism.  Do it 
this way
        # for portability
        UserDict.__init__(self)
        if d:
            self.update(d)

    def __getitem__(self, key):
        try:
            return self.data[key]
        except KeyError:
            if type(key) == StringType:
                return '%('+key+')s'
            else:
                return '<Missing key: %s>' % `key`