How can I validate forms in Flask?

How can I validate forms in Flask?

You can validate forms in Flask using the WTForms library. It provides a way to define forms and validate user input.

What are some common validation methods I can use?

Common validation methods include checking for required fields, validating email formats, and ensuring passwords meet complexity requirements.

Can you show me a simple example of a form with validation?

Sure! Here's a basic example:

from flask import Flask, render_template, request
from flask_wtf import FlaskForm
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import DataRequired, Email

app = Flask(__name__)
app.secret_key = 'your_secret_key'

class LoginForm(FlaskForm):
    email = StringField('Email', validators=[DataRequired(), Email()])
    password = PasswordField('Password', validators=[DataRequired()])
    submit = SubmitField('Login')

@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        # Process the form data
        return 'Form submitted successfully!'
    return render_template('login.html', form=form)

What if the validation fails?

If validation fails, you can display error messages to the user. WTForms provides a way to access these errors and show them in your template.