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How to Resolve Error "NameError: name 'json' is not defined" in Python

The NameError: name 'json' is not defined is a common Python error that occurs when you try to use JSON functionality without importing the necessary module. Unlike some other languages where standard libraries might be available globally, Python requires you to explicitly import modules before using them.

This guide explains why this error happens and provides the correct way to import and use the json module for serialization (converting objects to strings) and deserialization (converting strings to objects).

Understanding the Error​

When you write code like json.loads(...), Python looks for a variable or module named json in the current scope. If it hasn't been defined or imported, Python raises a NameError.

Faulty Code:

data = '{"id": 1, "name": "Alice"}'

# ⛔️ Error: 'json' is not defined because we forgot to import it
user = json.loads(data)

Output:

NameError: name 'json' is not defined

Solution 1: Importing the Entire Module (Standard)​

The most common and recommended fix is to import the entire module at the top of your script. This gives you access to all JSON functions (loads, dumps, load, dump) under the json namespace.

# ✅ Correct: Import the module first
import json

data = '{"id": 1, "name": "Alice"}'
user = json.loads(data)

print(user["name"])

Output:

Alice

Solution 2: Importing Specific Functions​

If you only need specific functions (like loads or dumps), you can import them directly into your namespace. This allows you to call them without the json. prefix.

# ✅ Correct: Import specific functions
from json import loads, dumps

data = {"id": 1, "name": "Bob"}

# Use dumps() directly
json_string = dumps(data)
print(json_string)

# Use loads() directly
user = loads(json_string)
print(user["name"])

Output:

{"id": 1, "name": "Bob"}
Bob

Solution 3: Using an Alias​

In scenarios where json might conflict with a variable name (though rare for this module) or if you prefer brevity, you can alias the module.

import json as j

data = {"id": 3, "name": "Charlie"}

# Use the alias 'j'
json_string = j.dumps(data)
print(json_string)

Output:

{"id": 3, "name": "Charlie"}

Practical Examples: Loading and Saving Data​

Once the module is imported correctly, here are the four core operations you will perform.

Serializing (Python -> JSON String)​

import json

data = {"key": "value"}
json_str = json.dumps(data)
print(data)

Deserializing (JSON String -> Python)​

import json

json_str = '{"key": "value"}'
data = json.loads(json_str)

Writing to a File​

import json

data = {"log": "system start"}
with open("log.json", "w") as f:
    json.dump(data, f)

Reading from a File​

import json

with open("log.json", "r") as f:
    data = json.load(f)

Conclusion​

To resolve NameError: name 'json' is not defined:

  1. Add import json at the top of your script.
  2. Verify Spelling: Ensure you typed import json (lowercase).
  3. Check Scope: Ensure the import is not inside a function that hasn't been called yet (though top-level imports are standard practice).

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