Convert CSV to Dictionary in Python

The best way to convert a CSV file to a Python dictionary is to create a CSV file object f using open("my_file.csv") and pass it in the csv.DictReader(f) method. The return value is an iterable of dictionaries, one per row in the CSV file, that maps the column header from the first row to the specific row value.

Let’s have a look at a simple example to demonstrate this solution next!

Basic Solution: CSV to Dict Example

Here’s the content of an example CSV file "my_file.csv" used in our code snippet below:

Name,Job,Age,Income
Alice,Programmer,23,110000
Bob,Executive,34,90000
Carl,Sales,45,50000

If you visualize this CSV in table form, it looks like this:

Here’s the code to convert that CSV file to multiple dictionaries, one dictionary per row by using the csv.DictReader(file) function:

import csv


csv_filename = 'my_file.csv'

with open(csv_filename) as f:
    reader = csv.DictReader(f)

    for row in reader:
        print(row)

A dictionary is a data structure that maps keys to values.

The output of the previous code snippet shows how the first row of the CSV is used as a header to determine the keys of the dictionary that are mapped to the values defined in the individual rows of the CSV file:

{'Name': 'Alice', 'Job': 'Programmer', 'Age': '23', 'Income': '110000'}
{'Name': 'Bob', 'Job': 'Executive', 'Age': '34', 'Income': '90000'}
{'Name': 'Carl', 'Job': 'Sales', 'Age': '45', 'Income': '50000'}

The csv.DictReader(f) method takes a file object f as an input argument. So, you first need to open the file using the built-in Python open() function.

🪲 Note: A common error is to pass the filename as a string—but this doesn’t work! The csv.DictReader(f) method expects a file object as a required argument.

🌍 Related Resource: You can learn how to convert a list of dictionaries back to a CSV by reading this tutorial on the Finxter blog.

One-Liner Solution: CSV to Dict

I love Python one-liners. That’s why I have written a book on those after all. 🙂

So, can we convert a CSV to a list of dictionaries in a single line of Python?

Of course, we can!

Here’s the one-liner that accomplishes the same as the code discussed before:

import csv; print(*csv.DictReader(open('my_file.csv')), sep='\n')

💡 Explanation: We import the csv module, use the semicolon ; to package two statements in one line, unpack * all rows from the csv.DictReader() output in a print statement, and use the newline character '\n' as a separator between two dictionary rows.

The output is the same as before:

{'Name': 'Alice', 'Job': 'Programmer', 'Age': '23', 'Income': '110000'}
{'Name': 'Bob', 'Job': 'Executive', 'Age': '34', 'Income': '90000'}
{'Name': 'Carl', 'Job': 'Sales', 'Age': '45', 'Income': '50000'}

If you just want to store the CSV contents in a list of dictionaries rather than printing them, you can use the following technique:

import csv; lst=[*csv.DictReader(open('my_file.csv'))]; print(lst)

The output is a list of dictionaries, one per (non-header) row of the original CSV:

[{'Name': 'Alice', 'Job': 'Programmer', 'Age': '23', 'Income': '110000'}, 
 {'Name': 'Bob', 'Job': 'Executive', 'Age': '34', 'Income': '90000'}, 
 {'Name': 'Carl', 'Job': 'Sales', 'Age': '45', 'Income': '50000'}]

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More Python CSV Conversions

🐍 Learn More: I have compiled an “ultimate guide” on the Finxter blog that shows you the best method, respectively, to convert a CSV file to JSON, Excel, dictionary, Parquet, list, list of lists, list of tuples, text file, DataFrame, XML, NumPy array, and list of dictionaries.