tryingsnake 0.2.0

Exception handling, the functional way.

TryingSnake

A simple, Try implementation inspired by scala.util.Try

Examples

• Wrap functions with arguments:

  >>> from tryingsnake import Try, Success, Failure
  
  >>> def succeed(): return 1
  >>> Try(succeed)
  Success(1)
  
  >>> def fail(): return 1/ 0
  >>> Try(fail)
  Failure(ZeroDivisionError('integer division or modulo by zero',))

• Avoid sentinel values:

  >>> def mean_1(xs):
  ...     try:
  ...       return sum(xs) / len(xs)
  ...     except ZeroDivisionError as e:
  ...         return None
  >>> mean_1([])  # What does it mean?

  vs.

  >>> def mean_2(xs): return sum(xs) / len(xs)
  >>> Try(mean_2, [])
  Failure(ZeroDivisionError('integer division or modulo by zero',))
  >>> Try(mean_2, ["foo", "bar"])
  Failure(TypeError("unsupported operand type(s) for +: 'int' and 'str'",))

• Follow the happy path:

  >>> def inc(x): return x + 1
  >>> def inv(x): return 1. / x
  
  >>> Success(1).map(inc).map(inv)
  Success(0.5)
  
  >>> Failure(Exception("e")).map(inc).map(inv)
  Failure(Exception('e',))
  
  >>> Success(-1).map(inc).map(inv)
  Failure(ZeroDivisionError('float division by zero',))

• Recover:

  >>> import urllib
  >>> def get(url): return urllib.urlopen(url).url
  >>> mirrors = ["http://mirror1.example.com", "http://example.com"]
  >>> Try(get, mirrors[0]).recover(lambda _: get(mirrors[1]))
  Success('http://example.com')

• Let them fail:

  >>> from operator import getitem
  >>> Try(getitem, [], 0)
  Failure(IndexError('list index out of range',))
  >>> Try_.set_unhandled([IndexError])
  >>> Try(getitem, [], 0)
  Traceback (most recent call last):
      ...
  IndexError: ...

INSTALLATION

pip install tryingsnake

or

easy_install tryingsnake

LICENSE

MIT, See LICENSE

FAQ

• Q: Is this project production-ready?

• A: No, and it probablly won’t be.

• Q: Why to use mixedCase method names instead of lowercase recommended by PEP8?

• A: Mostly to make switching between Python and Scala code as painless as possible.