Simple expression for variable in Python 3

Question

I need to use some float-type variables for two purposes: 1. To use it`s values for calculation of some function, 2. To change the values of these variables theirselves. I know how to do it generally, but I need to have simple short notation for my float-type variables. In the trivial example below I add two numbers, and my aim is to be able to write smth like 'f(a, i)' instead of 'a.vals[a.define_index[i]]' in the example below. I need to write simple notation both from left of '=' and from right of '=':

import numpy as np
class SomeClass(object):
    def __init__(self):
        self.vals=np.ones(10)
        self.define_index=[]
        for i in range(10):
            self.define_index.append(10-1-i)
a=SomeClass()
for i in range(10):
    a.vals[a.define_index[i]]=a.vals[a.define_index[i]]+1
print('sums =', a.vals)

R2RT · Accepted Answer · 2017-12-20 16:50:07Z

2

Seems you want to implement __getitem__ and __setitem__ for your type. It allows you to call a[i]. Doing so makes your type look like a list, so you might want to implement __iter__ as well so you could iterate over it with for loop.

import numpy as np
class SomeClass(object):
    def __init__(self):
        self.vals=np.ones(10)
        self.define_index=[]
        for i in range(10):
            self.define_index.append(10-1-i)

    def __getitem__(self, i):
        return self.vals[self.define_index[i]]

    def __setitem__(self, i, value):
        self.vals[self.define_index[i]] = value

    def __iter__(self):
        for i in self.define_index:
            yield self.vals[i]

a=SomeClass()
for i in range(10):
    a[i] += 1
print('sums =', a.vals)

for val in a: # iterate over data, hiding define_index
    print(val)

PS. I've shortened your incrementation to += 1

edited Dec 20, 2017 at 16:50

answered Dec 20, 2017 at 16:44

R2RT

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