How to convert sql varchar array to Python list?

I'm using psycopg2 for interacting with PostgreSQL database in Python2.7.

psycopg2 saves list in database at first in varchar field, and then I need simply to get the same Python list back.

Insert:

data = ['value', 'second value']
with psycopg2.connect(**DATABASE_CONFIG) as connection:
    cursor = connection.cursor()
    cursor.execute("INSERT INTO table_name (varchar_field) VALUES (%s)", (data)
    connection.commit()

In pgAdmin it looks like: {value, second_value}

Then I tried to do something like this:

with psycopg2.connect(**DATABASE_CONFIG) as connection:
    cursor = connection.cursor()
    cursor.execute("SELECT varchar_field FROM table_name")

    for row in cursor:
        for data_item in row: # here I want to iterate through the saved list (['value', 'second_value']), but it returns string: '{value, second_value}'
            print data_item

I have found possible solution, but I have no idea how to implement it in my code.

So, how can I retrieve back Python List from sql ARRAY type?

Copyright Notice：Content Author:「Dmitrijs Zubriks」，Reproduced under the CC 4.0 BY-SA copyright license with a link to the original source and this disclaimer.
Link to original article：https://stackoverflow.com/questions/21002999/how-to-convert-sql-varchar-array-to-python-list