Python – Convert CSV to List of Dictionaries

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Convert a CSV file to a list of Python dictionaries in three steps:

  • 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. Each dictionary maps the column header from the first row to the specific row value.
  • As the last step, convert the iterable of dictionaries to a list using the Python built-in list() function.

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

Basic Solution: CSV to List of Dicts – Example

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


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


Here’s the code to convert that CSV file to a list of 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)

lst = list(*reader)

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

The result of the previous code snippet is a list of dictionaries. 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.

πŸͺ² 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.

One-Liner Solution: CSV to List of Dicts

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

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; lst = list(*csv.DictReader(open('my_file.csv')))

πŸ’‘ Explanation: We import the csv module, use the semicolon ; to package two statements in one line, unpack * all rows from the csv.DictReader() output as arguments into the list() built-in function.

The result is stored in the variable lst that now holds the same list 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'}]

Here’s an alternative that is similar but also prints the list in a single line—now the unpacking happens into the bracket notation []:

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'}]

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.

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