Computer Science

1.11 Using Python-Greedy Algorithm: Creating A Meal Plan

Specification

In thislab you will writea greedy algorithm that creates a daily food plan according to some restrictions:

• The total calories must not exceed 2000.
• The plan must come as close as possible to matching a target amount of calories from one of the three macronutrients: protein, carbohydrates, or fat.

For example, the user might choose to set a goal of 30% protein for the daily meal plan. Your program will attempt to produce a meal plan that has a total of 2000 calories, with 30% of those calories coming from protein.

Supporting classes

Food class

A Food object represents a single serving of a food item that can be part of a meal plan.

Data members:

• name - a name to identify the food, for output display
• protein - grams of protein in one serving
• carbs - grams of carbohydrates in one serving
• fat - grams of fat in one serving
• calories - total calories in one serving (note that calories come from more than just protein, carbs and fat, so this number is greater than the sum of the three nutrients used in this lab)
• fraction - the fraction of a serving to be used in a meal plan (between 0.0 and 1.0, inclusive)
• protein_calories
• carbs_calories
• fat_calories

Methods:

set_fraction(p) - assigns the fraction data member with p (between 0.0 and 1.0 inclusive), and calculates new values for calories, protein_calories, carbs_calories and fat_calories accordingly.

__str__() - returns a string representing the food and nutrient contents.

MealPlan class

A MealPlan object is the collection of Food objects selected for a single day's meal plan.

Data members:

• foods - the list of Food objects that are part of the meal plan
• total_calories - total calories of the meal plan
• total_protein_calories - total calories from protein in the meal plan
• total_carbs_calories - total calories from carbohydrates in the meal plan
• total_fat_calories - total calories from fat in the meal plan

Provided methods:

• percent_nutrient(nutrient) - returns the current percent value (in range [0.0, 1.0]) of the given nutrient in the current meal plan, by calories.
• percent_nutrient_with_food(food, nutrient) - returns the total percent (in range [0.0, 1.0]) of the given nutrient if the given food were added. The food item is not added to the the meal plan by the method; the method is just for speculation only.
• calories_with_food(food) - returns the total calories the meal plan would have, if the given food were added. The food item is not added to the meal plan by this method; the method is just for speculation only.
• __str__() - returns a string listing the foods selected for the meal plan along with summary information about calorie content.

Methods for you to complete:

• fraction_to_fit_calorie_limit(food, calorie_limit) - returns the fraction (in the range [0.0, 1.0]) of a serving of the specified food item that is needed to make the entire meal plan exactly match the given calorie limit. If an entire serving can fit and the meal plan will be below the calorie limit, then the method returns 1.0. The food item is not added to the meal plan by this method; the method is just for speculation only.
• fraction_to_fit_nutrient_goal(food, nutrient, goal) - returns the fraction (in the range [0.0, 1.0]) of a serving of the specified food item that is needed to make the entire meal plan exactly match the given nutrient composition goal. If an entire serving can fit and the meal plan will be below the nutrient composition goal, then the method returns 1.0. The food item is not added to the meal plan by this method; the method is just for speculation only.
• meets_calorie_limit(calorie_limit, threshold) - returns True if the current meal plan has a total calorie content that falls within the given threshold of the specified calorie limit, otherwise returns False.
• meets_nutrient_goal(nutrient, goal, threshold) - returns True if the current meal plan has a total percent nutrient composition (by calories) that falls within the given threshold of the specified composition goal, otherwise returns False.

Be sure to read the description of each method carefully, and test them individually with various values to be sure they work correctly. The main algorithm will depend on these methods working properly!

The main program

When the program is executed, the user is prompted for some information:

• the name of the food data file (a string entered from an input prompt)
• the nutrient (protein, carbs or fat) that the user wishes to set a goal for (selected from a menu)
• the goal amount (percent of calories) the selected nutrient must compose of the meal plan (a float value entered from an input prompt)

Example: selecting a meal plan with 30% protein from the nutrients_1000.txt data file:

-----

Enter name of food data file: nutrients_1000.txt

1 - Set maximum protein

2 - Set maximum carbs

3 - Set maximum fat

4 - Exit program Enter choice (1-4): 1

What percentage of calories from protein is the goal? 30

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The program must be able to handle errors when entering the nutrient and nutrient goal information; when the user enters a value that is of the wrong type (like a string instead of an integer) or a value that is out of range, then an error message is displayed and the user is prompted again.

Once the information has been input from the user, the meal plan is created. You are to complete the function create_meal_plan(), which is called from the main program. The basic algorithm for building the meal plan is:

Sort the list of available foods according to the heuristic described below.

For each food item in the list:

• add the food if:
  • it is not "empty" (too few calories or too few of the target nutrient), and
  • an entire serving can be added, or
  • an entire serving can't be added, but there is a fraction of a serving that doesn't violate either constraint (total calories or percent nutrient)
• if the food item was added, check if the meal plan meets both the target calorie content and the percent nutrient content (within acceptable thresholds, as described below)
  • if the meal plan meets the requirements, exit the loop; otherwise continue to the next food item

display the final meal plan

Details

• A meal plan matches the calorie limit if total calories fall in the range [1999.9, 2000.1].
• A meal plan matches the nutrient goal if the total percent calories of the target nutrient comes within 0.1%. Ex. If the goal is 30% protein, a protein calorie content in the range [29.9%, 30.1%] is successful.
• Only allow fractional servings greater than or equal to 0.05.
• Only include Food objects with a calorie content greater than or equal to 0.1.
• Only include Food objects that are greater than or equal to 0.1% calories by the selected nutrient. Ex. If the selected nutrient is protein, ignore Food items where protein_calories / calories < 0.001.

Greedy algorithm heuristic

Iterate through the food item list in descending order of the user's selected nutrient percent composition. Ex. for setting maximum protein content, sort the Food object list by decreasing protein_calories.

Food data file

Food item information is in a text file with one food item specified per line. A food item line is formatted as follows:

• A text string representing the name of the food item, along with serving size information, followed by a colon (":");
• A float value representing the amount of protein in a single serving, in grams, followed by a comma (",");
• A float value representing the amount of carbohydrates in a single serving, in grams, followed by a comma (",");
• A float value representing the amount of fat in a single serving, in grams, followed by a comma (",");
• A float value representing the total calories in a single serving.

: , , ,

The food items do not appear in any particular order. You must complete the load_food_data() function to parse the data file line-by-line, and return a list of Food objects created from the parsed data.

Examples:

1. 30% protein

Enter name of food data file: nutrients_1000.txt

1 - Set maximum protein

2 - Set maximum carbs

3 - Set maximum fat

4 - Exit program Enter choice (1-4):

1 What percentage of calories from protein is the goal? 30

1: [1.0000] Beef, brisket, flat half, separable lean and fat, trimmed to 1/8" fat, choice, raw (1 steak / 434.0 grams) (P=78.6408,C=0.5208,F=96.131,E=1206.52) 2: [0.3207] Turkey, retail parts, drumstick, meat and skin, cooked, roasted (1 drumstick / 275.0 grams) (P=77.5775,C=0.0,F=25.7675,E=173.7324451060661) 3: [1.0000] Fast foods, submarine sandwich, turkey, roast beef and ham on white bread with lettuce and tomato (12 inch sub / 413.0 grams) (P=44.0258,C=84.0868,F=9.9946,E=602.98) 4: [0.0502] Cheese, mozzarella, nonfat (1 cup, shredded / 113.0 grams) (P=35.821,C=3.955,F=0.0,E=7.994115976331346) 5: [0.1840] Gravy, au jus, canned (1 can / 298.0 grams) (P=3.576,C=7.45,F=0.596,E=8.773438917602562) Total Calories: 2000.0 Protein: 0.30 Carbs: 0.17 Fat: 0.52

Program given to start with:

import sys, operator, random from nutrition import Food, MealPlan

# Constants to be used by the greedy algorithm. NUTRIENT_THRESHOLD = 0.001 FRACTION_THRESHOLD = 0.05 CALORIE_THRESHOLD = 0.1 MAX_CALORIES = 2000

def load_nutrient_data(filename): # Open file, read food items one line at a time, # createFood objects and append them to a list. # Return the list once the entire file is processed. return []

def sort_food_list(foods, nutrient): # Sort the food list based on the percent-by-calories of the # given nutrient ('protein', 'carbs' or 'fat') # The list is sorted in-place; nothing is returned. pass def create_meal_plan(foods, nutrient, goal): # A greedy algorithm to create a meal plan that has MAX_CALORIES # calories and the goal amount of the nutrient (e.g. 30% protein) plan = MealPlan() return plan def print_menu(): print() print("\t1 - Set maximum protein") print("\t2 - Set maximum carbohydrates") print("\t3 - Set maximum fat") print("\t4 - Exit program") print()

if __name__ == "__main__": # 1. Load the food data from the file (change this to a user # prompt for the filename) filename = food_data_small.txt foods = load_nutrient_data(filename) # 2. Display menu and get user's choice. Repeat menu until a # valid choice is entered by the user (1-4, inclusive). # 3. Prompt user for goal nutrient percent value. Repeat prompt # until a valid choice is entered by the user (0-100, inclusive) # 4. Run greedy algorithm tocreate the meal plan. plan = createMealPlan(foods, nutrient, goal) # 5. Display plan. print(plan)