Michal Ludvig wrote:
Hi all,
when I've got a string, say:
URL="http://xyz/blah?session=%(session)s&message=%(message)s"
is it possible to fill in only 'session' and leave "%(message)s" as is
when it isn't present in the values dict?
For example:
URL % { 'session' : 123 }
raises KeyError because of missing 'message' in the dict.
I could indeed replace '%(session)s' with a string replace or regexp but
that's not very elegant ;-)
Is there any way to tell the formatter to use only what's available and
ignore the rest?
You could write a class inheriting from dict which, for example, returns
"%(key)s" if the key "key" is absent:
>>> class IgnoreDict(dict):
def __getitem__(self, key):
try:
return dict.__getitem__(self, key)
except KeyError:
return "%%(%s)s" % key
>>> d = {'session': 123}
>>> URL = "http://xyz/blah?session=%(session)s&message=%(message)s"
>>> URL % d
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
URL % d
KeyError: 'message'
>>> URL % IgnoreDict(d)
'http://xyz/blah?session=123&message=%(message)s'
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