Writing to a CSV File Using Data from Two Dictionaries

What will you learn?

In this tutorial, you will master the art of combining data from two dictionaries and exporting it into a CSV file using Python. This skill is crucial for efficient data manipulation and storing structured information in a format that is easily accessible and widely compatible.

Introduction to the Problem and Solution

Working with dictionaries is common due to their effectiveness in storing key-value pairs. However, there comes a point where we need to export this data, either for reporting or sharing purposes. The Comma-Separated Values (CSV) format is popular for its simplicity and compatibility across various platforms and software.

The challenge lies in merging two dictionaries that may represent related datasets and transforming them into rows in a CSV file. The goal is not only to accomplish this task but also to ensure that our solution can adapt to different types of dictionary data seamlessly.


import csv

# Sample dictionaries
dict1 = {'John': 25, 'Alice': 22}
dict2 = {'Jake': 30, 'Jill': 28}

# Combine dictionaries into a list of tuples
combined_data = list(dict1.items()) + list(dict2.items())

# Specify the filename for writing
filename = "combined_data.csv"

with open(filename, 'w', newline='') as csvfile:
    csvwriter = csv.writer(csvfile)

    # Write headers (optional)
    csvwriter.writerow(['Name', 'Age'])

    # Write the combined data
    for item in combined_data:

# Copyright PHD


  • Combining Dictionaries: Merge dict1 and dict2 by converting their items into lists and concatenating them.
  • Opening a File: Use open() with ‘w’ mode for writing, ensuring no extra newlines are inserted.
  • Creating a CSV Writer Object: Utilize csv.writer() to write sequences into the specified file as CSV rows.
  • Headers: Optionally define column headers ([‘Name’, ‘Age’]) before writing actual content.
  • Writing Data Rows: Iterate through the combined list of tuples to insert each as its own row within the CSV file.
    How do I append data instead of overwriting it?

    To append data, change ‘w’ mode in open() function call to `’a’.

    Can I include more than two dictionaries?

    Absolutely! You can combine any number of dictionaries by extending the concatenation step accordingly.

    What if my dictionaries have different keys?

    Ensure all keys you intend on writing are represented across your header row(s). Consider preprocessing steps if keys differ significantly or values are missing.

    How do I handle non-string values?

    For complex types, consider converting them into strings first or flattening your structure before writing.

    Is there an alternative way without using csv.writer()?

    Yes! You can use pandas DataFrame objects which provide additional flexibility when dealing with complex structures.


    Mastering the process of writing combined dictionary values into a well-formatted CSV file enhances data sharing and analysis capabilities while ensuring interoperability across diverse systems. Understanding effective serialization practices is essential for handling heterogeneous datasets encountered in modern computational tasks.

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