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How to read JSON file in Python: Syntax and Examples

Using the json module

Python provides a built-in module called `json` that allows us to work with JSON data. This module provides methods for reading and writing JSON files. To read a JSON file in Python, we need to import the `json` module.

The `json` module provides two main methods for reading JSON files: `load()` and `loads()`. The `load()` method is used to read a JSON file directly, while the `loads()` method is used to read a JSON string.

In this article, we will focus on how to read a JSON file using the `load()` method.

Opening and reading a JSON file

To read a JSON file in Python, we first need to open the file using the `open()` function. The `open()` function takes two arguments: the file path and the mode in which we want to open the file. In this case, we want to open the file in read mode, so we pass `’r’` as the mode.

Once the file is open, we can use the `load()` method from the `json` module to read the contents of the file. The `load()` method takes the file object as an argument and returns a Python object representing the JSON data.

Here is the syntax to read a JSON file in Python:

«`python
import json

# Open the JSON file
with open(‘file.json’, ‘r’) as f:
# Read the contents of the file
data = json.load(f)
«`

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In the above code, we import the `json` module and open the JSON file using the `open()` function. We then use the `json.load()` method to read the contents of the file and store it in the `data` variable.

Accessing data from a JSON file

Once we have read the JSON file and stored its contents in a Python object, we can access the data using the same syntax as accessing elements in a dictionary.

JSON data is organized in a key-value format, where each key represents a field and each value represents the corresponding data. To access a specific value, we need to specify the key associated with that value.

For example, let’s say we have a JSON file named `data.json` with the following contents:

«`json
{
«name»: «John»,
«age»: 30,
«city»: «New York»
}
«`

To access the value of the `name` field, we can use the following code:

«`python
import json

# Open the JSON file
with open(‘data.json’, ‘r’) as f:
# Read the contents of the file
data = json.load(f)

# Access the value of the ‘name’ field
name = data[‘name’]
«`

In the above code, we read the contents of the JSON file and store it in the `data` variable. We then access the value of the `name` field by using `data[‘name’]` and store it in the `name` variable.

Handling errors when reading a JSON file

When reading a JSON file in Python, it is important to handle any potential errors that may occur. The most common error that can occur is a `JSONDecodeError`, which is raised when the JSON data is not valid.

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To handle this error, we can use a `try-except` block. In the `try` block, we read the JSON file using the `json.load()` method. If the JSON data is valid, the code will execute without any errors. However, if the JSON data is not valid, a `JSONDecodeError` will be raised.

Here is an example of how to handle errors when reading a JSON file:

«`python
import json

try:
# Open the JSON file
with open(‘file.json’, ‘r’) as f:
# Read the contents of the file
data = json.load(f)
except json.JSONDecodeError:
print(«Invalid JSON data»)
«`

In the above code, we use a `try-except` block to handle any potential `JSONDecodeError` that may occur. If the JSON data is valid, the code inside the `try` block will execute without any errors. However, if the JSON data is not valid, the code inside the `except` block will execute and print the error message «Invalid JSON data».

Example: Reading a JSON file in Python

Let’s put everything together and see an example of how to read a JSON file in Python:

«`python
import json

try:
# Open the JSON file
with open(‘data.json’, ‘r’) as f:
# Read the contents of the file
data = json.load(f)

# Access the values from the JSON data
name = data[‘name’]
age = data[‘age’]
city = data[‘city’]

# Print the values
print(«Name:», name)
print(«Age:», age)
print(«City:», city)
except json.JSONDecodeError:
print(«Invalid JSON data»)
«`

In the above code, we open the JSON file named `data.json` and read its contents using the `json.load()` method. We then access the values of the `name`, `age`, and `city` fields and print them.

If the JSON data is valid, the output will be:

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«`
Name: John
Age: 30
City: New York
«`

If the JSON data is not valid, the output will be:

«`
Invalid JSON data
«`

In conclusion, reading a JSON file in Python is a straightforward process. By using the `json` module and its `load()` method, we can easily read the contents of a JSON file and access the data within it. It is important to handle any potential errors that may occur when reading the JSON file to ensure the code runs smoothly.

Author

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