3 ms·

I think the best is a little of both ways. For instance in python: x = some_dict['meh'] Will raise if 'meh' doesn't exist. If you believe that 'meh' should

by phzbOx 15y ago

I think the best is a little of both ways. For instance in python: x = some_dict['meh'] Will raise if 'meh' doesn't exist. If you believe that 'meh' should be there in your program, it's fine to 'let it raise an exception'. However, if 'meh' could be there, it's better to use an error style such as: x = some_dict.getDefault('meh', 'some-neutral-value') And continue without raising because there's no need to raise as there's nothing exceptional here. Ideally, raising an exception should have the meaning "Hey, something is wrong here and I don't know what to do next". And someone in the call hierarchy would handle this and say "Oh, the connection stopped.. that's why it's not working. I'll reconnect and call you again". And note that this "parent handling" might be way higher than where the problem occurred..

gaius 15y ago
You mean collections.defaultdict http://docs.python.org/library/collections.html#collections.defaultdict http://docs.python.org/library/collections.html#collections....
- TylerE 15y ago
  No he doesn't. defaultdict provides a default value for ALL missing values. His approach allows him to target one key in particular, and is a very common python idiom.
  - gaius 15y ago
    I'm confused - where does that come from? >>> x.getDefault(1, 'Que?') Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> x.getDefault(1, 'Que?') AttributeError: 'dict' object has no attribute 'getDefault'
    - TylerE 15y ago
      Because it's actually (somewhat confusingly, called setdefault). >>> a = {1:'foo',2:'blah'} >>> a.setdefault(1,'default') 'foo' >>> a.setdefault(4,'default') 'default' >>> a {1: 'foo', 2: 'blah', 4: 'default'} This actually updates the underlying datastructure. Very handy when you want to deal with nested structures, since you can do something like: matches.setdefault(keyword,[]).append(s) This will append s to the list in matches[keyword] if it exists, or set matches[keyword] to [] and then append.
  - phzbOx 15y ago
    Wops, you both are right, thanks for pointing it out. I meant to say dict.get, i.e. {'a':1}.get('b',5)
deleted 15y ago
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by phzbOx 15y ago

gaius 15y ago

You mean collections.defaultdict http://docs.python.org/library/collections.html#collections.defaultdict http://docs.python.org/library/collections.html#collections....

TylerE 15y ago
No he doesn't. defaultdict provides a default value for ALL missing values. His approach allows him to target one key in particular, and is a very common python idiom.
- gaius 15y ago
  I'm confused - where does that come from? >>> x.getDefault(1, 'Que?') Traceback (most recent call last): File "<pyshell#2>", line 1, in <module> x.getDefault(1, 'Que?') AttributeError: 'dict' object has no attribute 'getDefault'
  - TylerE 15y ago
    Because it's actually (somewhat confusingly, called setdefault). >>> a = {1:'foo',2:'blah'} >>> a.setdefault(1,'default') 'foo' >>> a.setdefault(4,'default') 'default' >>> a {1: 'foo', 2: 'blah', 4: 'default'} This actually updates the underlying datastructure. Very handy when you want to deal with nested structures, since you can do something like: matches.setdefault(keyword,[]).append(s) This will append s to the list in matches[keyword] if it exists, or set matches[keyword] to [] and then append.
- phzbOx 15y ago
  Wops, you both are right, thanks for pointing it out. I meant to say dict.get, i.e. {'a':1}.get('b',5)

deleted 15y ago

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