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Python Python Collections (2016, retired 2019) Dictionaries String Formatting with Dictionaries

Posted by Rodwell Mazambara
Rodwell Mazambara
1,402 Points

string_factory throwing KeyError

When I run this code I get a KeyError for the key 'name'. Where am I getting it wrong?

string_factory.py 
# Example:
# values = [{"name": "Michelangelo", "food": "PIZZA"}, {"name": "Garfield", "food": "lasagna"}]
# string_factory(values)
# ["Hi, I'm Michelangelo and I love to eat PIZZA!", "Hi, I'm Garfield and I love to eat lasagna!"]

template = "Hi, I'm {name} and I love to eat {food}!"

def string_factory(list_of_dicts):  
    food_preferences_list=[]
    for food_dict in list_of_dicts:
        for name,food in food_dict.items():
            template.format(name,food)
            food_preferences_list.append(template)

    return food_preferences_list

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,426 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,426 Points

Your solution is close. There are some items to fix:

  • Using the dict method .items() is not going to work yo intended as it return the key / value pair for each entry in the dict, such as "food", "Pizza". Perhaps you meant .values()?
  • The format method creates a new string (because strings are immutable) this newly formatted string is not captured by another variable so gets dropped. The code is appending the same template every time.
  • The template string is using named fields, to be sure the format arguments are properly received keyword arguments are needed: ...format(name=name, food=food)
  • using food_dicts.values() will return both items, but since it is a dictionary, the order of the items is not guaranteed, meaning that it might be food,name or name, food. There are various ways around this:
    • drop the inner for loop and use double-asterisk expansion: `...format(**food_dict)
    • explicitly expand the food_dict ...format(name=food_dict['name'],food=food_dict['food'])

Post back if you need more help. Good luck!!

Edited: Misread using items instead of values. Corrected the above text.

Rodwell Mazambara
Rodwell Mazambara
1,402 Points

Thanks Chris. You are a saviour! This worked:

template = "Hi, I'm {name} and I love to eat {food}!"

def string_factory(list_of_dicts):  
  food_preferences_list=[]
  for food_dict in list_of_dicts:                                     
       food_string=template.format(**food_dict)
       food_preferences_list.append(food_string)      
  return food_preferences_list