django-forms - Django中cleaned_data和cleaned_data.get的区别

Question

我看过一些示例代码，例如:

    def clean_message(self):
    message = self.cleaned_data['message']
    num_words = len(message.split())
    if num_words < 4:
        raise forms.ValidationError("Not enough words!")
    return message

以及一些示例，例如:

def clean(self):
    username = self.cleaned_data.get('username')
    password = self.cleaned_data.get('password')
    ...
    self.check_for_test_cookie()
    return self.cleaned_data

两者有什么区别？

Answer 1

.get() 基本上是从 dictionary 中获取元素的快捷方式.我通常使用 .get()当我不确定字典中的条目是否会在那里时。例如:

>>> cleaned_data = {'username': "bob", 'password': "secret"}
>>> cleaned_data['username']
'bob'
>>> cleaned_data.get('username')
'bob'
>>> cleaned_data['foo']
    Traceback (most recent call last):
      File "<stdin>", line 1, in <module>
    KeyError: 'foo'
>>> cleaned_data.get('foo')  # No exception, just get nothing back.
>>> cleaned_data.get('foo', "Sane Default")
'Sane Default'