Python | Find depth of a dictionary

Prerequisite: Nested dictionary The task is to find the depth of given dictionary in Python. Let’s discuss all different methods to do this task. Examples:

Input : {1:'a', 2: {3: {4: {}}}}
Output : 4

Input : {'a':1, 'b': {'c':'geek'}}
Output : 3

Approach #1 : Naive Approach A naive approach in order to find the depth of a dictionary is to count the number of opening curly braces. But, one drawback of this approach is that it would only work if the input is correct. 

Python3

# Python3 Program to find depth of a dictionary
def dict_depth(dic, level = 1):

    str_dic = str(dic)
    counter = 0
    for i in str_dic:
        if i == "{":
            counter += 1
    return(counter)

# Driver code
dic = {1:'Geek', 2: {3: {4: {}}}}
print(dict_depth(dic))

Output:

4

Approach #2: Using recursion In this method we use recursion with max() function which picks the greatest depth for the current dictionary under scrutiny at each level. 

Python3

# Python3 Program to find depth of a dictionary
def dict_depth(dic, level = 1):

    if not isinstance(dic, dict) or not dic:
        return level
    return max(dict_depth(dic[key], level + 1)
                               for key in dic)

# Driver code
dic = {1:'a', 2: {3: {4: {}}}}

print(dict_depth(dic))

Output:

4

Another version of the recursive solution is to use map() function by which the values of the inner dictionary is mapped to the called function. 

Python3

# Python3 Program to find depth of a dictionary
def dict_depth(my_dict):
    if isinstance(my_dict, dict):

        return 1 + (max(map(dict_depth, my_dict.values()))
                                    if my_dict else 0)

    return 0

# Driver code
my_dict = {1:'a', 2: {3: {4: {}}}}
print(dict_depth(my_dict))

Output:

4

Approach #3: Iterative Solution In this approach, we save the nested key and its initial depth in a variable, say p_dict. Now, start a loop for p_dict, and keep popping values while digging deeper for nested dictionaries. 

Python3

# Python3 Program to find depth of a dictionary
def dict_depth(myDict):

    Ddepth = 1
    obj = [(k, Ddepth + 1) for k in myDict.values()
                          if isinstance(k, dict)]
    max_depth = 0

    while(obj):
        n, Ddepth = obj.pop()
        max_depth = max(max_depth, Ddepth)

        obj = obj + [(k, Ddepth + 1) for k in n.values()
                                 if isinstance(k, dict)]

    return max_depth

# Driver code
myDict = {1:'a', 2: {3: {4:{}}}}
print(dict_depth(myDict))

Output:

4