CODEWITHSUNDEEP
pythonclassoverloadingargument-passing
pylang
pylang

Reputation: 44545

Is there a way to pass arguments using the dot operator in python?

I'd like to the make a clean, "smart" method that performs specific operations without passing in arguments. I have some code that works in principle as follows:

class Foo():
    def __init__(self, spam='spam', ham='ham'):
        self.spam = spam
        self.ham = ham

    def bar(self, arg):
        # spam operation
        if arg == self.spam:
            return self.spam*2
        # ham operation
        elif arg == self.ham:
            return self.ham*3

Notice the bar method is written to perform different operations on spam and ham. Implementing this code would return:

foo = Foo()
foo.bar(foo.spam)                      # returns 'spamspam'
foo.bar(foo.ham)                       # returns 'hamhamham'

Unfortunately, I'm having to use foo twice to access a specific operation in bar, which is awkward and tedious. Is there a cleaner, Pythonic way to get the same results without passing in arguments? For example, is it possible to overload the dot (.) operator to the get the same results with:

# Ideal 1
foo = Foo()
foo.bar.spam                          # bar knows to use spam operation
foo.bar.ham                           # bar knows to use ham operation

or even better

# Ideal 2
foo = Foo()
foo.spam.bar                          # bar knows to use spam operation
foo.ham.bar                           # bar knows to use ham operation

Upvotes: 4

Views: 3360

Answers (1)

salparadise
salparadise

Reputation: 5805

EDIT: Updated to parametize the options.

Here is something using object composition:

class Pork(object):
    def __init__(self, name, mult):
        self.name = name
        self.mult = mult

    @property
    def bar(self):
        return self.name * self.mult

    def __repr__(self):
        return self.name

class Foo(object):
    def __init__(self, spam='spam', ham='ham'):
        self.spam = Pork(spam, 2)
        self.ham = Pork(ham, 3)

Results:

In [638]: foo = Foo()

In [639]: foo.spam.bar
Out[639]: 'spamspam'
In [641]: foo.ham.bar
Out[641]: 'hamhamham'

Upvotes: 2

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