Write a dictionary to a file in Python
Last Updated : 01 Apr, 2025
A dictionary store data using key-value pairs. Our task is that we need to save a dictionary to a file so that we can use it later, even after the program is closed. However, a dictionary cannot be directly written to a file. It must first be changed into a format that a file can store and read later. Let’s explore different methods to achieve this.
Using json.dump()
json.dump() function directly writes the dictionary as a JSON object into a file making it easy to read and retrieve later. Since JSON is a text-based format, it can be opened easily and is better for readability purposes.
Python import json d = {'Name': "Bob",'Age': 28 } # writing dictionary to a file as JSON with open('data.json', 'w') as f: json.dump(d, f) Output:
data.json file
Explanation: After defining the dictionary, a file named ‘data.json’ is opened in write mode (‘w’), allowing data to be stored in it. Finally, the json.dump(d, f) function is used to directly write the dictionary into the file in JSON format, ensuring that the data is structured and can be easily retrieved later.
Using json.dumps()
json.dumps() function converts a dictionary into a JSON-formatted string, which can then be written to a file manually using write(). This allows adding formatting options like indentation for better readability.
Python import json d = {'Name': "Bob", 'Age': 28} # Convert dictionary to a JSON string and write to file with open('data.json', 'w') as file: file.write(json.dumps(d, indent=4)) Output:
data.json file
Explanation: json.dumps(d, indent=4) function is used to convert it into a JSON-formatted string with indentation for better readability. Finally, the write() method is used to store this formatted JSON string in the file, ensuring that the data remains structured and easy to read when accessed later.
Using pickle.dump()
pickle module allows saving a dictionary in binary format, preserving its exact structure. The dump() function serializes the dictionary and writes it to a binary file, which can later be retrieved using load().
Python from types import resolve_bases import pickle d = {'Name': "bob", 'Age': 28} # writing dictionary to a binary file with open('data.pkl', 'wb') as file: pickle.dump(d, file) # Reading dictionary from the binary file with open('data.pkl', 'rb') as file: res = pickle.load(file) print(res) Output:
data.pkl file
{'Name': 'bob', 'Age': 28}Explanation: pickle.dump(d, file) function serializes the dictionary and writes it to the file, preserving its structure. Later, the same file is opened in binary read mode (‘rb’), and the pickle.load(file) function is used to deserialize the stored data, converting it back into a dictionary.
Using str()
The simplest way to store a dictionary in a file is by converting it into a string using str(), then writing it using write(). This method, however, does not provide a structured format and requires additional processing when reading the data back.
Python d = {'Name': "Bob", 'Age': 28} # Convert dictionary to string and write to file with open('data.txt', 'w') as file: file.write(str(d)) Output:
data.txt file
Explanation: str(d) function is used to convert the dictionary into a string format, which is then written to the file using the write() method.
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