JSON

Basic JSON rules

• Keys must use double quotes "name"
• String values must also use double quotes "Alan"
• Supported data types
  • string: "hi"
  • number: 123, 3.14
  • boolean: true, false (lowercase — not True/False)
  • null: null (not None)
  • object: { ... }
  • array: [ ... ]
• No comments allowed
• No trailing commas (no extra comma at the end) {"a": 1}

json.dumps()

• json.dumps turns a Python dictionary into a JSON string. 
  • With a dictionary, you can use f-strings for dynamic values, then pass the result to APIs that require a JSON string.

import json
 
# 用 f-string 拼变量
account_id = "123456789012"
user_name = "assignment1_User"
 
# Python dictionary
policy = {
    "Version": "2012-10-17",
    "Statement": [{
        "Effect": "Allow",
        "Principal": {"AWS": f"arn:aws:iam::{account_id}:root"},
        "Action": "sts:AssumeRole",
        "Resource": f"arn:aws:iam::{account_id}:user/{user_name}",
    }],
}
 
# dict → JSON 字符串
trust = json.dumps(policy)
 
print(trust)
# {"Version": "2012-10-17", "Statement": [{"Effect": "Allow", "Principal": {"AWS": "arn:aws:iam::123456789012:root"}, "Action": "sts:AssumeRole", "Resource": "arn:aws:iam::123456789012:user/assignment1_User"}]}