Recursive function nested dictionary python

Question

I need to call a recursive function to print the contents of the nested dictionary like this on separate lines:

lunch : {"sandwich": 2, "chips": 1, "drink": 1}

dinner : {"ribs": 6, "mac_cheese": 1, "roll": 1, "pie": 1}

I tried the following code but it is just iterating over the keys of the nested dictionary

# recursive function for printing out meal plans 
def print_meals(meal_plan):
    for key, value in meal_plan.items():
        if type(value) is dict:
            print_meals(value)
        else:
            print(key, ":", value)

    # create an empty dictionary
    meal_plan = {}

    # create individual dictionaries for each meal
    lunch = {"sandwich": 2, "chips": 1, "drink": 1}
    dinner = {"ribs": 6, "mac_cheese": 1, "roll": 1, "pie": 1}

    #create a nested dictionary
    meal_plan["lunch"] = lunch 
    meal_plan["dinner"] = dinner 

    # call recursive function 'print_meals'
    print_meals(meal_plan)

Where is the nested dictionary in input? I could see , all are plain dictionary. — John Byro
– John Byro, Commented Oct 16, 2021 at 12:48
@JohnByro I am creating the nested dictionary under the comment for create a nested dictionary. It is being stored in the dictionary meal_plan — python_beginner
– python_beginner, Commented Oct 16, 2021 at 12:53
Is it guaranteed that there will only be one level of depth in the nested dictionary? Or could you have for instance meal_plan = {'monday': {'lunch': {...}, 'dinner': {...}}, 'tuesday': {...}} — Stef
– Stef, Commented Oct 16, 2021 at 12:55
I recommend using isinstance(value, dict) rather than type(value) is dict. For instance, if value is a subclass of dict, then isinstance(value, dict) will still return True, but type(value) is dict will return False. — Stef
– Stef, Commented Oct 16, 2021 at 14:55
If there aren't arbitrary levels of nesting you don't need recursion. — ggorlen
– ggorlen, Commented Oct 16, 2021 at 17:46

Mahdi F. · Accepted Answer · 2021-10-16 12:57:57Z

1

you can define your function like below:

>>> def print_meals(dct):
...    for k,v in dct.items():
...        print(f'{k} : {v}');print()

Output:

>>> meal_plan
{'lunch': {'sandwich': 2, 'chips': 1, 'drink': 1},
 'dinner': {'ribs': 6, 'mac_cheese': 1, 'roll': 1, 'pie': 1}}

>>> print_meals(meal_plan)
lunch : {'sandwich': 2, 'chips': 1, 'drink': 1}

dinner : {'ribs': 6, 'mac_cheese': 1, 'roll': 1, 'pie': 1}

answered Oct 16, 2021 at 12:57

Mahdi F.

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Comments

Stef · Accepted Answer · 2021-10-16 13:08:36Z

Here is an idea:

def print_meals(meal_plan, depth=0):
    if isinstance(meal_plan, dict):
        for k, v in meal_plan.items():
            print('  '*depth, k, ':')
            print_meals(v, depth+1)
    else:
        print('  '*depth, meal_plan)

print_meals('sandwich')
#  sandwich

print_meals({'sandwich': 1})
#  sandwich :
#    1

print_meals({'lunch': {'sandwich': 2, 'chips': 1, 'drink': 1}, 'dinner': {'ribs': 6, 'mac_cheese': 1, 'roll': 1, 'pie': 1}})
#  lunch :
#    sandwich :
#      2
#    chips :
#      1
#    drink :
#      1
#  dinner :
#    ribs :
#      6
#    mac_cheese :
#      1
#    roll :
#      1
#    pie :
#      1

print_meals({'monday': {'lunch': {'sandwich': 1, 'apple': 2}, 'dinner': {'soup': 1, 'yaourt': 1}}, 'tuesday': {'breakfast': 'pain au chocolat', 'lunch': {'salad': 2, 'lasagna': 1}, 'dinner': {'beans':3}}})
#  monday :
#    lunch :
#      sandwich :
#        1
#      apple :
#        2
#    dinner :
#      soup :
#        1
#      yaourt :
#        1
#  tuesday :
#    breakfast :
#      pain au chocolat
#    lunch :
#      salad :
#        2
#      lasagna :
#        1
#    dinner :
#      beans :
#        3

Alternatively, for fewer line breaks, but assumes the meal plan is a dict:

def print_meals(meal_plan, depth=0):
  for k,v in meal_plan.items():
    if isinstance(v, dict):
      print('  '*depth, k, ':')
      print_meals(v, depth+1)
    else:
      print('  '*depth, k, ':', v)

print_meals({'sandwich': 1})
#  sandwich : 1

print_meals({'lunch': {'sandwich': 2, 'chips': 1, 'drink': 1}, 'dinner': {'ribs': 6, 'mac_cheese': 1, 'roll': 1, 'pie': 1}})
#  lunch :
#    sandwich : 2
#    chips : 1
#    drink : 1
#  dinner :
#    ribs : 6
#    mac_cheese : 1
#    roll : 1
#    pie : 1

print_meals({'monday': {'lunch': {'sandwich': 1, 'apple': 2}, 'dinner': {'soup': 1, 'yaourt': 1}}, 'tuesday': {'breakfast': 'pain au chocolat', 'lunch': {'salad': 2, 'lasagna': 1}, 'dinner': {'beans':3}}})
#  monday :
#    lunch :
#      sandwich : 1
#      apple : 2
#    dinner :
#      soup : 1
#      yaourt : 1
#  tuesday :
#    breakfast : pain au chocolat
#    lunch :
#      salad : 2
#      lasagna : 1
#    dinner :
#      beans : 3

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