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A little language for schema-enforced models.

Project description

Fame is a framework for metamodelling in Python.

  • Entities are described by models
  • Models are described by metamodels
  • Models have fields, derived fields and constraints
  • Entities can have custom fields
  • Entities can be created even if data is invalid
  • There are functions to validate and get error messages
  • Validation checks presence and type of fields
  • Validation checks all constraints
  • Derived fields are memoized

Example

class Experiment(Model):

    @schema
    def metamodel(self, m):
        m.field('name', str)
        m.field('subject', options(
            'user',
            'visitor',
            'email',
            'listing',
            'market'
        ))
        m.field('treatments', array(str))
        m.field('percent_exposed', int, default=100)
        m.field('design', nullable(regexp('^https?')))

    @derived_field
    def is_miscellanous(self):
        return self.subject not in ['user', 'visitor']

    @constraint("expected percent_exposed to not exceed 100, got {}")
    def constraint(self):
        if self.percent_exposed > 100:
            return self.percent_exposed

Conventions

  • Define metamodel function first
  • Then define derived field functions
  • Then define all the constraint functions
  • Constraint functions are all named “constraint”, that is intentional

Installation

To install this package, run

pip install fame

Contributing

Bug reports and pull requests are welcome on github at, https://github.com/akuhn/py-fame

Project details


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