问题
What does the coerce argument do in django forms? I've read the documentation, but its not very helpful, so a good explanation with a few examples of use cases would be helpful. To quote the documentation:
A function that takes one argument and returns a coerced value. Examples include the built-in int, float, bool and other types. Defaults to an identity function.
回答1:
TypedChoiceField is just like ChoiceField, except ChoiceField always return unicode.
With TypedChoiceField you pass a function that takes one argument and returns the value cast to the type you want. For example, if you want to coerce the value to integer, use:
int_field = forms.TypedChoiceField(choices=SOME_CHOICES, coerce=int)
The field value will always be an integer or fail validation.
来源：https://stackoverflow.com/questions/18200545/coerce-in-django-forms