Getting an empty output when calculating two same numbers and unable to change key name in dict w/ R-CodePudding

Edit: I was able to figure out the first part of this question by adding a condition that if the cost and paid are the same and matches a key value in money then it adds it to the dict.

I'm sorry if the title is confusing. Basically, I am writing a function that takes in a number as the item cost and the second as the amount you paid with. Then it tells you your change in bills and coins.

  def right_change(cost, paid):

  money = {
    "$20 bill" : 20,
    "$10 bill" : 10,
    "$5 bill" : 5,
    "$1 bill": 1,
    "quarter": 0.25,
    "dime" : 0.10,
    "nickel": 0.05,
    "penny": 0.01
  }

  amount = paid - cost
  change = {}
  
  for item in money:
    while amount >= money[item]:
      amount -= money[item]
      amount = float(f'{amount:.2f}')
      if item not in change:
          change[item] = 1
      else:
          change[item]  = 1

I get the expected output when I use floats such as (5.40, 20) --> {$10 bill: 1, $1 bill: 4, quarter: 2, dime: 1} But if I use exact numbers like (20, 20) it will return an empty object when I want {$20 bill: 1}

I am also trying to change the names to plurals if their quantity is more than 1. In order to be less redundant and typing out conditions for each word, I tried using Regex:

def plurals(dict):
  new_dict = {}
  for item in dict:
    if dict[item] > 1 and re.match('/[^y]$/gm', item):
      new_dict[item "s"] = dict[item]
      if re.match('p', item):
          new_dict['pennies'] = dict[item]
    else:
        new_dict[item] = dict[item]

  return new_dict

It will still output the change but it won't change anything. Any help is appreciated! I've been spending hours trying to figure this out.

CodePudding user response：

For the name change issue:

def set_to_plural_if_more_than_one(old_dict):
    new_dict = {}
    for item in old_dict:
        if old_dict[item] > 1:
            if item[-1] == "y":
                new_dict[item[:-1]   "ies"] = old_dict[item]
            else:
                new_dict[item   "s"] = old_dict[item]
        else:
            new_dict[item] = old_dict[item]
    return new_dict

You can use regex but I feel like in this case it's an overkill since you are simply distinguishing between some basic strings you know and not searching for any advanced patterns.

Also just in general I would avoid overwriting names of pythons builtins such as dict as variable or argument names in your code since they can cause weird and sometimes hard to debug behaviour.