Convert List of Dictionaries to Dictionary of Lists - Python

We are given a list of dictionaries we need to convert it to dictionaries of lists. For example, we are given a list of dictionaries li = [{'manoj': 'java', 'bobby': 'python'}, {'manoj': 'php', 'bobby': 'java'}, {'manoj': 'cloud', 'bobby': 'big-data'}] we need to convert this to dictionary of list so that the output becomes {'manoj': ['java', 'php', 'cloud'], 'bobby': ['python', 'java', 'big-data']}.

Using Pandas

Using Pandas, a list of dictionaries can be converted to a dictionary of lists by creating a DataFrame and utilizing the to_dict() method with orient='list'. This maps each key in the dictionaries to a list of its corresponding values.

{'manoj': ['java', 'php', 'cloud'], 'bobby': ['python', 'java', 'big-data']}

Explanation:

• pd.DataFrame(li): When we call this , it takes the list li and turns it into a table-like structure where each dictionary becomes a row.
• .to_dict(orient="list"): This method converts the DataFrame into a dictionary where each column becomes a key and the values are lists containing all entries for that column.

Using defaultdict

Defaultdictfrom Python's collections module is useful when we need to append to lists within a dictionary. It automatically initializes the dictionary keys with a default value in this case, an empty list, simplifying the process of appending data.

{'manoj': ['java', 'php', 'cloud'], 'bobby': ['python', 'java', 'big-data']}

Explanation:

• defaultdict(list) creates a dictionary where each key automatically has an empty list as its default value.
• For i in li: This loop iterates through each dictionary in li. Then for each dictionary, we loop through its key-value pairs and append the value to the corresponding list in res under that key.

Using dictionary comprehension

This method uses dictionary comprehension to convert a list of dictionaries into a dictionary where each key maps to a list of values from the original dictionaries. The values for each key are collected across all dictionaries in the list.

{'manoj': ['java', 'php', 'cloud'], 'bobby': ['python', 'java', 'big-data']}

Explanation: dictionary comprehension iterates over each key in the first dictionary (li[0]) and for each key, it collects the corresponding values from all dictionaries in the list li into a list.

Using zip

zip function can be efficiently used to convert alist of dictionaries into a dictionary of lists. In this approach, the values from each dictionary are grouped by keys and zip is used to transpose the list of values, so we can easily convert them into lists.

{'manoj': ['java', 'php', 'cloud'], 'bobby': ['python', 'java', 'big-data']}

Explanation:

• zip(*[d.values() for d in li]) extracts values from each dictionary and transposes them.
• zip(li[0].keys(), ...) pairs the keys ('manoj', 'bobby') with their corresponding values from the transposed tuples.
• {key: list(value) for key, value in ...} constructs a dictionary where each key maps to a list of corresponding values.