The Best Input Validation Libraries for Python Developers | by Everything Programming | Coinmonks | Sep, 2023

Everything Programming
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Input validation is a critical aspect of software development. It ensures that the data your application receives is valid, secure, and meets the expected criteria. Python developers have a plethora of libraries at their disposal to simplify input validation. In this article, we will explore some of the best input validation libraries for Python and provide code snippets and explanations for each.

pydantic is a data validation and parsing library. It allows you to define data schemas using Python classes, making it easy to validate and parse incoming data.

from pydantic import BaseModel

class User(BaseModel):
username: str
age: int
user_data = {"username": "john_doe", "age": 30}
user = User(**user_data)

Here, we define a User class with the expected data fields and their types. pydantic handles the validation and parsing of user_data.

WTForms is a popular library for form handling and validation in web applications. It provides a simple and flexible way to define forms and validate user input.

from wtforms import Form, StringField, IntegerField, validators

class UserForm(Form):
username = StringField("Username", [validators.Length(min=4, max=25)])
age = IntegerField("Age", [validators.NumberRange(min=18, max=99)])
form = UserForm(username="john_doe", age=30)

In this example, we create a UserForm class with fields and validation rules, making it easy to handle form submissions.

cerberus is a lightweight and extensible data validation library that can validate complex data structures using simple and intuitive rules.

from cerberus import Validator

schema = {"username": {"type": "string", "minlength": 4, "maxlength": 25},
"age": {"type": "integer", "min": 18, "max": 99}}
v = Validator(schema)
document = {"username": "john_doe", "age": 30}
is_valid = v.validate(document)

Here, we define a validation schema using cerberus and validate the document against it.

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