introduce
wtforms is a form component that supports multiple web frameworks, mainly used for form validation and generation,
Install
pip install wtforms
use
Customize a class, inherit the wtforms.Form class, and define fields
from wtforms import Form
from wtforms.fields import simple,core,html5 # fields come from here
from wtforms import validators # validation rules come from here
from wtforms import widgets # tools are here
class LoginForm(Form):
user = simple.StringField(
label='username', # prompt information
validators=[validators.DataRequired(message='Username cannot be empty.')], #List of validation rules
widget=widgets.TextInput(), # Render the input tag in the way he defines first
render_kw={'class': 'form-control'} # Set properties for the input tag
)
render
Instance custom class object, passed into the template, if data is passed in the instance object, the data will be rendered into the input box
{{ form.name }} # The input box of the field
{{ form.name.label }} # This field prompts information
{{ form.name.errors[0] }} # The error information of the field, it is recommended to use this method, the following error information of the field will throw an exception
{{ form.errors }} # full error message
# You can also use a for loop, and its order will not be confused, because a counter is maintained inside the Form
{% for item in form %}
<p>{{item.label}}: {{item}} {{item.errors[0] }}</p>
{% endfor %}
verify
Instance custom class object is to pass data
form = LoginForm(formdata=request.form)
if form.validate():
# Verification passed, print data
print(form.data)
else:
print(form.error) # print error message
field
Three packages simple, core, html5 are provided in wtforms.fields
simple is simple and commonly used including:
['BooleanField', 'TextAreaField', 'PasswordField', 'FileField',
'HiddenField', 'SubmitField', 'TextField']
core is less commonly used
(
'BooleanField', 'DecimalField', 'DateField', 'DateTimeField', 'FieldList',
'FloatField', 'FormField', 'IntegerField', 'RadioField', 'SelectField',
'SelectMultipleField', 'StringField',
)
The tags in html5 have their own regularity (browser verification)
(
'DateField', 'DateTimeField', 'DateTimeLocalField', 'DecimalField',
'DecimalRangeField', 'EmailField', 'IntegerField', 'IntegerRangeField',
'SearchField', 'TelField', 'URLField',
)
It should be noted here that core.RadioField (single selection), core.SelectField (drop-down menu), core.SelectMultipleField (multiple selection drop-down menu) have a coerce attribute, which specifies the type of data conversion (because the data obtained from the front end are all String), if it is not converted to the corresponding data type, the validation will fail.
In addition, if we want to dynamically obtain the value of choices, we can rewrite the __init__ method in the class we wrote. Get it every time you instantiate it, and then execute the __init__ in the parent class to get it in real time. updated options
class RegisterForm(Form):
city = core.SelectField(
label='city',
choices=SQLHelper.fetch_all('select id,name from city',{},None),
coerce=int
)
def __init__(self, *args, **kwargs):
super(RegisterForm, self).__init__(*args, **kwargs)
self.city.choices = PymysqlConn.fetch_all('select id,name from city',{},None)
validation rules
A number of validation rules are provided in wtforms.validators
(
'DataRequired', 'data_required', 'Email', 'email', 'EqualTo', 'equal_to',
'IPAddress', 'ip_address', 'InputRequired', 'input_required', 'Length',
'length', 'NumberRange', 'number_range', 'Optional', 'optional',
'Required', 'required', 'Regexp', 'regexp', 'URL', 'url', 'AnyOf',
'any_of', 'NoneOf', 'none_of', 'MacAddress', 'mac_address', 'UUID'
)
Here are some commonly used
DataRequired: non-null validation, message=error message
Email: Email format verification, message=error message
Length: length verification, min=shortest, max=longest, message=error message
Regexp: regular match, regex regular expression, message=error message
EqualTo: Is it the same as the value of other fields, fieldname=other field name, message=error message
Custom Validation-Hook
# Set validation for a field
def validate_fieldname(self, field):
print(field.data) # The value passed from the current field
print(self.data) # All values currently passed in: name, gender.....
if validation failed:
raise validators.ValidationError("Continue subsequent validation")
# raise validators.StopValidation("Do not continue subsequent validation")
small parts
wtforms.widgets provides many form styles, each field has a default widget, and the rendered style can be modified by setting the widget
('CheckboxInput', 'FileInput', 'HiddenInput', 'ListWidget', 'PasswordInput',
'RadioInput', 'Select', 'SubmitInput', 'TableWidget', 'TextArea',
'TextInput', 'Option')
Checkbox settings
favor = core.SelectMultipleField(
label='Preferences',
choices=(
(1, 'basketball'),
(2, 'football'),
),
widget=widgets.ListWidget(prefix_label=False),
option_widget=widgets.CheckboxInput(),
coerce=int,
default=[1, 2]
)