I need to make a custom validator in WTForms where the input is to be: number:number - e.g. 2:1
match1 = StringField('Russia-Saudi Arabia', validators=[DataRequired()])
So, my question is - how to create such validator?
I've looked upon the documentation at http://wtforms.readthedocs.io/en/latest/validators.html, but was not very helpful (for me) in this case.
Thanks in advance
You can write a custom validator within a form by writing a validate_{field_name} method. If it raises a ValidationError, the form will not be valid and will display the error.
For your specific case, here's a solution using regex. It finds the match for the string, and then uses a bit of splitting to get back the scores. After validating the form you can access the scores by form.score1, form.score2.
import re
from flask_wtf import FlaskForm
from wtforms import ValidationError
class MatchForm(FlaskForm):
match1 = StringField("Russia-Saudi Arabia", validators=[DataRequired()])
def validate_match1(self, form, field):
if not re.search(r"^[0-9]+:[0-9]+$", field.data):
raise ValidationError("Invalid input syntax")
s1, s2 = form.data.split(":")
form.score1 = int(s1)
form.score2 = int(s2)
def validate_match1(self, form, field) or you can make the method static with @staticmethod
from wtforms import ValidationError seems to be missed. Please consider editing this answer.from flask_wtf import FlaskForm
from wtforms import StringField, validators
# Define a custom validator function
def custom_validator(form, field):
if len(field.data) < 5:
raise validators.ValidationError('Input must be at least 5 characters long')
# Define a Flask form with a StringField and a custom validator
class MyForm(FlaskForm):
my_field = StringField('My Field', validators=[validators.InputRequired(), custom_validator])
