How to Read Properties File in Python?

We can use jproperties module to read properties file in Python. A properties file contains key-value pairs in each line. The equals (=) works as the delimiter between the key and value. A line that starts with # is treated as a comment.

Installing jproperties Library

This module is not part of the standard installation. We can install jproperties module using PIP.

# pip install jproperties

Reading Properties File in Python

I have created a properties file for our example: app-config.properties.

# Database Credentials
DB_HOST=localhost
DB_SCHEMA=Test
DB_User=root
DB_PWD=root@neon

The first step is to import the Properties object into our Python program and instantiate it.

from jproperties import Properties

configs = Properties()

The next step is to load the properties file into our Properties object.

with open('app-config.properties', 'rb') as config_file:
    configs.load(config_file)

Recommended Reading: Python with Statement

Now, we can read a specific property using get() method or through the index. The Properties object is very similar to a Python Dictionary.

The value is stored in a PropertyTuple object, which is a named tuple of two values - data and meta. The jproperties support properties metadata too, but we are not interested in that here.

print(configs.get("DB_User"))  
# PropertyTuple(data='root', meta={})

print(f'Database User: {configs.get("DB_User").data}')  
# Database User: root

print(f'Database Password: {configs["DB_PWD"].data}')  
# Database Password: root@neon

We can use len() function to get the count of properties.

print(f'Properties Count: {len(configs)}')  
# Properties Count: 4

What if the key doesn’t exist?

If the key doesn’t exist, the get() method will return None.

random_value = configs.get("Random_Key")
print(random_value)  # None

But, if we use the index then KeyError is raised. In that case, it’s better to handle this exception using try-except block.

try:
    random_value = configs["Random_Key"]
    print(random_value)
except KeyError as ke:
    print(f'{ke}, lookup key was "Random_Key"')

# Output:
# 'Key not found', lookup key was "Random_Key"

Printing All the Properties

We can use the items() method to get a collection of Tuple, which contains keys and corresponding PropertyTuple values.

items_view = configs.items()
print(type(items_view))

for item in items_view:
    print(item)

Output:

<class 'collections.abc.ItemsView'>
('DB_HOST', PropertyTuple(data='localhost', meta={}))
('DB_SCHEMA', PropertyTuple(data='Test', meta={}))
('DB_User', PropertyTuple(data='root', meta={}))
('DB_PWD', PropertyTuple(data='root@neon', meta={}))

Since we are looking to print key=value as the output, we can use the following code.

for item in items_view:
    print(item[0], '=', item[1].data)

Output:

DB_HOST = localhost
DB_SCHEMA = Test
DB_User = root
DB_PWD = root@neon

Getting List of Keys from the Properties File

Here is a complete program to read the properties file and create a list of all the keys.

from jproperties import Properties

configs = Properties()

with open('app-config.properties', 'rb') as config_file:
    configs.load(config_file)

items_view = configs.items()
list_keys = []

for item in items_view:
    list_keys.append(item[0])

print(list_keys)  
# ['DB_HOST', 'DB_SCHEMA', 'DB_User', 'DB_PWD']

Python Read Properties File into Dictionary

A properties file is the same as a dictionary. So, it’s a common practice to read the properties file into a dictionary. The steps are similar to above, except for the change in the iteration code to add the elements to a dictionary.

db_configs_dict = {}

for item in items_view:
    db_configs_dict[item[0]] = item[1].data

print(db_configs_dict)
# {'DB_HOST': 'localhost', 'DB_SCHEMA': 'Test', 'DB_User': 'root', 'DB_PWD': 'root@neon'}

Reference: PyPI jproperties page