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  • Book Overview & Buying Flask Framework Cookbook
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Flask Framework Cookbook

Flask Framework Cookbook

By : Shalabh Aggarwal
4.3 (4)
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Flask Framework Cookbook

Flask Framework Cookbook

4.3 (4)
By: Shalabh Aggarwal

Overview of this book

If you are a web developer who wants to learn more about developing applications in Flask and scale them with industry-standard practices, this is the book for you. This book will also act as a handy tool if you are aware of Flask's major extensions and want to make the best use of them. It is assumed that you have knowledge of Python and a basic understanding of Flask. If you are completely new to Flask, reading the book from the first chapter and going forward will help in getting acquainted with Flask as you go ahead.
Table of Contents (14 chapters)
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13
Index

Creating custom fields and validation


Apart from providing a bunch of fields and validations, Flask also provides the flexibility to create custom fields and validations. Sometimes, we might need to parse some form of data that cannot be processed using the available current fields. In such cases, we can implement our own fields.

How to do it…

In our catalog application, we used SelectField for the category, and we populated the values for this field in our create_product() method on a GET request. It would be much more convenient if we did not bother about this and the population of this field was taken care of by itself. Let's implement a custom field for this in models.py:

class CategoryField(SelectField):

    def iter_choices(self):
        categories = [(c.id, c.name) for c in Category.query.all()]
        for value, label in categories:
            yield (value, label, self.coerce(value) == self.data)

    def pre_validate(self, form):
        for v, _ in [(c.id, c.name) for c in Category...
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