Most validation can be done using `validators`_ - simple helpers that can be
reused easily. Validators are simple functions (or callables) that take a single
argument and raise ``ValidationError`` on invalid input. Validators are run
-inside the ``run_validators`` method that is called from ``Field.clean`` once
-the value is validated by the field's methods.
+after the field's ``to_python`` and ``validate`` methods have been called.
Validation of a Form is split into several steps, which can be customized or
FloatField will turn the data into a Python ``float`` or raise a
- * Next step resides in ``validate()`` method. This is a method where all
- field-specific validation, that cannot be abstracted into a validator,
- should take place. It takes the value coerced to correct datatype and
- raises ``ValidationError`` on any error. This method does not return
- anything and shouldn't alter the value.
+ * The ``validate()`` method on a Field handles field-specific validation
+ that is not suitable for a validator, It takes the value coerced to
+ correct datatype and raises ``ValidationError`` on any error. This method
+ does not return anything and shouldn't alter the value. You should
+ override it to handle validation logic that you don't want to put in a
- * Validators are run in the ``run_validators`` method. This method
- aggregates all the errors from all validators run into a single
+ * The ``run_validators()`` method on a Field runs all of the field's
+ validators and aggregates all the errors into a single
+ ``ValidationError``. You shouldn't need to override this method.
* The ``clean()`` method on a Field subclass. This is responsible for
running ``to_python``, ``validate`` and ``run_validators`` in the correct
def to_python(self, value):
"Normalize data to a list of strings."
- # return empty list on empty input
- if not value: return 
+ # Return an empty list if no input was given.
def validate(self, value):
"Check if value consists only of valid emails."
check if value is given if the field is required