The document discusses building REST APIs in Flask. It introduces REST concepts and how Flask supports REST. Validation of resources can be done with Trafaret. The document demonstrates creating API resources with Flask extensions that support validation, authentication decorators, and modeling SQL Alchemy classes. Future work includes adding filtering, caching, throttling and customizing fields for modeled resources.

1. REST in Flask
raising

2. the

3. service
I am: Yehor Nazarkin
Follow me: @nimnull
Email me: nimnull@gmail.com
Saturday, June 2, 12

4. RESTin

5. pieces
• Representative state transfer
• Hypertext transfer protocol:
✓ URL endpoint as resource address
✓ Content-Type
✓ Status codes
• The Web is REST
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6. RESTin

7. pieces
Web Front Mobile client
API
Backends
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8. Why Flask? as

9. we

10. already

11. have

12. tones

13. of

14. stuff
• I’m not a framework junkie
• I want to customize, not rewrite
• Clean codebase (20 python modules)
• Aware of django.contrib.admin, django.form, etc.
• Lack of ORM functionality
✓ I don’t like to write raw SQL
✓ I need composite keys
✓ I want to optimize for a DB backend (we are
on PostgreSQL)
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15. Why Flask? as

16. we

17. already

18. have

19. tones

20. of

21. stuff
Because we can
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22. Validation resource

23. tier,

24. model

25. tier
Trafaret http://pypi.python.org/pypi/trafaret
import trafaret as t
t.Dict({'first_name': t.String,
'last_name': t.String,
'phone': t.String,
t.Key('role_id', optional=True): t.Int
}).ignore_extra('*')
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26. Validation resource

27. tier,

28. model

29. tier
Key subset:
t.Dict({'first_name': t.String,
te.KeysSubset('pass', 'confirm'): cmp_pwds})
def cmp_pwds(value):
if value['pass'] != value['confirm']:
return {'confirm': t.DataError(Doesn't match)}
return {'pass': value['pass']}
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30. Validation resource

31. tier,

32. model

33. tier
Type check:
• Null, Bool, String, Int, Float, List, Dict
• Atom, Email, URL, Enum, Callable
• Converters, ignorance, excludes, optional keys
@guard(a=String, b=Int, c=String)
def guarded(a, b, c):
return a, b, c
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34. Achievements yes,

35. we

36. did
Based on Flask’s MethodView
Extended with method-decorators
Simple to attach
Resource — for generic cases
ModelResource — SQLA mapped classes
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37. Achievements yes,

38. we

39. did
Inspired by
• django-tastypie
• flask-restless
• rainbows and unicorns
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40. Achievements yes,

41. we

42. did
In Practice
@api_resource(account, 'sessions', {'id': None})
class SessionResource(Resource):
validation = t.Dict({'email': t.Email}).allow_extra('*')
@api_resource(account, 'addresses', {'id': int})
class AddressResource(ModelResource):
validation = t.Dict({'city': t.String,
'street': t.String,
'type': t.String(regex=(bill|delivery))}
).allow_extra('*')
model = Address
def get_objects(self):
...
def get_object(self):
...
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43. Achievements yes,

44. we

45. did
Differences
@api_resource(account, 'profiles', {'id': None})
class RoleResource(ModelResource):
validation = ...
decorators = [login_required, ]
method_decorators = {'post': check_permission('is_superuser'),
'put': check_permission('is_superuser')}
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46. Roadmap no,

47. we

48. don’t
To be done
• Filtering (DSL?)
• Caching
• Throttling
• Customizing field set for ModelResource
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49. Questions? write

50. code,

51. not

52. hollywar
Saturday, June 2, 12