ActiveState Code

Recipe 271669: Ruby like syntactic sugar

Ruby offers very nice language constructs for loops or for iterating over lists like the following: 5.times { print "Hello World" }. This recipe shows a hack how to implement these features in python.

Python 
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class Times:
    def __rmul__(self,n):
        for i in range(n):
            self.func()
    def __call__(self,func):
        self.func=func
        return self
times=Times()

class Each:
    def __rmul__(self,L):
        return map(self.func,L)
    def __call__(self,func):
        self.func=func
        return self
each=Each()

class Length:
    def __rmul__(self,L):
        return len(L)
length=Length()

def printf(x):
    print x

5 *times(lambda: printf("Hello"))
[1,2,3,4] *each(lambda x: printf("Count:"+str(x)))
print [1,2,3,4,5] *length
['a','b','c','d','e'] *each(lambda char: char+'!')

Discussion

This is only a fun recipe and you should not use this programming style because it can lead to a lot of confusions. Using this style you can define methods for classes that are normally capsuled like numbers and lists. I would wish python would provide a nicer way to do this.

Comments

  1. 1. At 12:45 p.m. on 4 mar 2004, Paul Reznicek said:

    Some improvements. Nice (although map can do nearly the same), here a small improvement:

    class Repeat:
    def __rmul__(self,n):
        for i in range(n):
            if self.passCurrentIndex:
                self.kwargs.update({'currentIndex':i})
                self.func(*self.args,**self.kwargs)
            else:
                self.func(*self.args,**self.kwargs)
    def __call__(self,func,*args,**kwargs):
        self.func=func
        self.args=args
        self.passCurrentIndex=kwargs.pop('passCurrentIndex',None)
        self.kwargs=kwargs
        return self
repeat=Repeat()

# PRINT usable as FUNCTION
def printf(*args):
    print ' '.join(args)

# usage:
5 * repeat(printf, 'Hello', 'World')

# test index argument
def testRepeat(*args,**kwargs):
    print ' '.join(args), 'index=',
    print kwargs.get('currentIndex','USE passCurrentIndex=True TO ACTIVATE')

5 * repeat(testRepeat, 'Hello', 'World')
5 * repeat(testRepeat, 'Hello', 'World', passCurrentIndex=True)

    Frankly, Python is the best for me and I can't imagine a

    better way to do language wraps like in Python.

    Paul

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