 | pyswitchA simple yet powerful 'switch'-like dispatcher system for Python |
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A simple yet powerful 'switch'-like dispatcher system for Python pyswitch is a simple yet powerful 'switch'-like dispatcher for Python. It's inspired by the C language switch statement, but with more flexibility; case values are not limited to integers like in C, but can be any value usable with the '==' equality operator, or any string usable on the left-hand side of the 'in' operator, or any regular expression. Iterables of these types can also be use as case values.Example:Here's a small example of its use:>>> from pyswitch import Switch, SwitchError# Instantiate a Switch object.>>> mySwitch = Switch()# Register some cases and case handlers, using the handy-dandy# decorators provided by the Switch object.# A default handler. A default handler is optional. If defined,# it will be called for all switch values not handled by any other# handler. If not defined, a SwitchError will be raised for an unhandled# switch value.# All handlers are passed the value being switched on, along with any# other optional positional and keyword parameters given to the switch.# Handlers can return a value, which is then returned by the call to# switch which caused the handler to be called.# Naturally, handlers can do anything you want. In this default case# example, we return a string of interesting info.>>> @mySwitch.default... def gotDefault(value, *args, **kwargs):... return "Default handler: I got unregistered value %r, "\... "with args: %r and kwargs: %r" % \... (value, args, kwargs)# A single numeric case value. The 'case' decorator is for exact matching# to the switch value. The value given to the case function, called# the case value, can be any type usable with the '==' equality operator.>>> @mySwitch.case(0)... def gotZero(value, *args, **kwargs):... return "gotZero: I got a %d, with args: %r and kwargs: %r" % \... (value, args, kwargs)# A range of numeric case values. An iterable of values can be given# as the case value.>>> @mySwitch.case(range(5, 10))... def gotFiveThruNine(value, *args, **kwargs):... return "gotFiveThruNine: I got a %d, with args: %r and kwargs: %r" % \... (value, args, kwargs)# A string case value, for an exact match.>>> @mySwitch.case('Guido')... def gotGuido(value, *args, **kwargs):... return "gotGuido: I got '%s', with args: %r and kwargs: %r" % \... (value, args, kwargs)# A string value for use with the 'in' operator.>>> @mySwitch.caseIn('lo')... def gotLo(value, *args, **kwargs):... return "gotLo: I got '%s', with args: %r and kwargs: %r" % \... (value, args, kwargs)# A regular expression pattern match in a string.# You can also pass in a pre-compiled regular expression.# For caseRegEx, the value passed to the case handler is actually# the Match Object resulting from the successful regular expression# pattern match.>>> @mySwitch.caseRegEx(r'\b(y\w*)\b')... def gotPyword(matchObj, *args, **kwargs):... return "gotPyword: I got a matchObject where group(1) is '%s', "\... "with args: %r and kwargs: %r" % \... (matchObj.group(1), args, kwargs)# And lastly, you can pass a iterable of mixed-type values to case,# caseIn, and caseRegEx. Here, we pass in a list of heterogenous# values to be use for exact matches.>>> @mySwitch.case()... def gotStuffInSeq(value, *args, **kwargs):... return "gotStuffInSeq: I got %r, with args: %r and kwargs: %r" % \... (value, args, kwargs)# Now show what we can do.>>> mySwitch(0, testing=False)"gotZero: I got a 0, with args: () and kwargs: {'testing': False}">>> mySwitch(6, flag='boring')"gotFiveThruNine: I got a 6, with args: () and kwargs: {'flag': 'boring'}">>> mySwitch(10, 42)'Default handler: I got unregistered value 10, with args: (42,) and kwargs: {}'>>> mySwitch('Guido', BDFL=True)"gotGuido: I got 'Guido', with args: () and kwargs: {'BDFL': True}">>> mySwitch('Anyone seen Guido around?')"Default handler: I got unregistered value 'Anyone seen Guido around?', with args: () and kwargs: {}">>> mySwitch('Yep, and he said "hello".', 99, yes='no')"gotLo: I got 'lo', with args: (99,) and kwargs: {'yes': 'no'}">>> mySwitch('Bird is the Python word of the day.')"gotPyword: I got a matchObject where group(1) is 'Python', with args: () and kwargs: {}">>> mySwitch('yo')"gotStuffInSeq: I got 'yo', with args: () and kwargs: {}" Requirements: · Python What's New in This Release: It's no longer necessary to call the switch method of the Switch class to dispatch a value, as the __call__ method is now a synonym. So instead, you can use: · mySwitch = Switch() · ... register your cases ... · returnValue = mySwitch(value_to_switch_on) · But the switch method is still there for backwards compatibility.
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