Itertools combinations: How to get the ids of the first fitting value combination-CodePudding

I have a record with a unique ID and an associated value in EURO. Now I want to get the first combination of values that matches a value I defined. So far I only get the combination of the values, but I would like to have the IDs of the respective values also in the output.

Actual result:

List->  20.5 10.0 12.0

Desired result:

List-> 1:20.5 3:10.0 5:12.0

Two separated list would also be fine

Here is my first approach:

from itertools import combinations
import numpy as np
import pandas as pd

# initialize list of lists
data = [[1 , 20.5], [2 , 32.0], [3 , 10.0], [4 , 5.0], [5 , 12.0], [6 , 10.0], [7, 2.0], [8 , 1.0], [9 , 6.0], [10 , 3.0], [11, 2.0]]
 
# Create the pandas DataFrame
df = pd.DataFrame(data, columns=['ID', 'EUR'])
summed_amount = 42.5

# Get All Possible Combinations Of Numbers In List
for value in range(1, len(df)  1):
    possible_combination = list(combinations(df['EUR'], value))
    #get the first values which equals the desired amount (summed_amount)
    li =[each for each in possible_combination if sum(each) == summed_amount]
    if li:
        print("List-> ", *li[0])
        break

RESULT:

List->  20.5 10.0 12.0

Thanks and kind regards :)

CodePudding user response：

There are some ways you can do that. You need to somehow store the values with their ids. You can do workarounds in pandas for that, or do a more elegant solution with your own custom class. Take a look:

class MyAmount(object):
  def __init__(self, id, value):
    self.id = id
    self.value = value

  def __radd__(self, other):
    return self.value   (other.value if isinstance(other, MyAmount) else other)
    
  def __repr__(self):
    return "{}: {}".format(self.id, self.value)

Here we create our own class, MyAmount, with our own custom logic. Then, we can just create MyAmount objects for each row.

amounts = df.apply(lambda s: MyAmount(s.ID, s.EUR), axis=1)

Now, just keep your code, but make sure to use amounts to find the combinations.

possible_combination = list(amounts, value))

Since we overrode the __radd__ magic function, sum(each) will sum over the value property of MyAmount. And since we overrode __repr__, when you print a MyAmount object, you'll display a string with format id: value.

You can customize this however you want.