Python Save Dictionary To File

In this lesson, you’ll learn how to save a dictionary to a file in Python. Also, we’ll see how to read the same dictionary from a file.

In this lesson, you’ll learn how to:

• Use the pickle module to save the dictionary object to a file.
• Save the dictionary to a text file.
• Use the dump() method of a json module to write a dictionary in a json file.
• Write the dictionary to a CSV file.

How to save a dictionary to file in Python

Example: save a dictionary to file

Let’s see the below example of how you can use the pickle module to save a dictionary to a person_data.pkl file.

import pickle

# create a dictionary using {}
person = {"name": "Jessa", "country": "USA", "telephone": 1178}
print('Person dictionary')
print(person)

# save dictionary to person_data.pkl file
with open('person_data.pkl', 'wb') as fp:
    pickle.dump(person, fp)
    print('dictionary saved successfully to file')Code language: Python (python)

Output:

Person dictionary
{'name': 'Jessa', 'country': 'USA', 'telephone': 1178}
dictionary saved successfully to file

Read Dictionary from a File

Now read the same dictionary from a file using a pickle module’s load() method.

Example:

import pickle

# Read dictionary pkl file
with open('person_data.pkl', 'rb') as fp:
    person = pickle.load(fp)
    print('Person dictionary')
    print(person)Code language: Python (python)

Output:

Person dictionary
{'name': 'Jessa', 'country': 'USA', 'telephone': 1178}

Save a dictionary to a text file using the json module

We can use the Python json module to write dictionary objects as text data into the file. This module provides methods to encode and decode data in JSON and text formats.

We will use the following two methods of a json module.

• The dump() method is used to write Python objects as JSON formatted data into a file.
• Using the load() method, we can read JSON data from text, JSON, or a binary file to a dictionary object.

Let’s see the below example of how you can use the json module to save a dictionary to a text file.

import json

# assume you have the following dictionary
person = {"name": "Jessa", "country": "USA", "telephone": 1178}
print('Person dictionary')
print(person)

print("Started writing dictionary to a file")
with open("person.txt", "w") as fp:
    json.dump(person, fp)  # encode dict into JSON
print("Done writing dict into .txt file")Code language: Python (python)

Output:

Person dictionary
{'name': 'Jessa', 'country': 'USA', 'telephone': 1178}

Started writing dictionary to a file
Done writing dict into .txt file

Note: You can also use the dump() method to write a dictionary in a json file. Only you need to change the file extension to json while writing it.

Read a dictionary from a text file.

Now, let’s see how to read the same dictionary from the file using the load() function.

import json

# Open the file for reading
with open("person.txt", "r") as fp:
    # Load the dictionary from the file
    person_dict = json.load(fp)

# Print the contents of the dictionary
print(person_dict)Code language: Python (python)

Output:

{'name': 'Jessa', 'country': 'USA', 'telephone': 1178}

Save the dictionary to a CSV file

The Python csv library provides functionality to read from and write to CSV files.

• Use the csv.DictReader() method to read CSV files into a dictionary.
• Use the csv.DictWriter() method to write a dictionary to a CSV file.

Example: Save the dictionary to a CSV file.

import csv

# Dictionary to be saved
person = {"name": "Jessa", "country": "USA", "telephone": 1178}
print('Person dictionary')
print(person)

# Open a csv file for writing
with open("person.csv", "w", newline="") as fp:
    # Create a writer object
    writer = csv.DictWriter(fp, fieldnames=person.keys())

    # Write the header row
    writer.writeheader()

    # Write the data rows
    writer.writerow(person)
    print('Done writing dict to a csv file')Code language: Python (python)

Output:

Person dictionary
{'name': 'Jessa', 'country': 'USA', 'telephone': 1178}

Done writing dict to a csv file

Example: Read a dictionary from a csv file

import csv

# Open the csv file for reading
with open("person.csv", "r") as infile:
    # Create a reader object
    reader = csv.DictReader(infile)

    # Iterate through the rows
    for row in reader:
        print(row)Code language: Python (python)

Output:

OrderedDict([('name', 'Jessa'), ('country', 'USA'), ('telephone', '1178')])

Note: This will read the contents of the person.csv file and create a dictionary for each row in the file. You can then iterate through the rows and access the values in the dictionary using the column names as keys.