AWS提供了多种方式向API用户通知变更，以下是一些解决方法的示例代码：

1. 使用AWS SNS（Simple Notification Service）发送通知：

import boto3

# 创建SNS客户端
sns_client = boto3.client('sns')

# 发送通知
def send_notification(topic_arn, message):
    sns_client.publish(
        TopicArn=topic_arn,
        Message=message
    )

# 示例用法
topic_arn = 'arn:aws:sns:us-west-2:123456789012:my-topic'
message = 'API发生了变更，请注意更新'
send_notification(topic_arn, message)

2. 使用AWS CloudWatch事件规则和Lambda函数发送通知：

import boto3

# 创建CloudWatch事件客户端
events_client = boto3.client('events')

# 创建Lambda客户端
lambda_client = boto3.client('lambda')

# 创建事件规则
def create_event_rule(rule_name, schedule_expression, target_arn):
    response = events_client.put_rule(
        Name=rule_name,
        ScheduleExpression=schedule_expression,
        State='ENABLED',
        Description='API变更通知规则',
        EventPattern='{}',
    )

    # 添加目标
    response = events_client.put_targets(
        Rule=rule_name,
        Targets=[
            {
                'Id': '1',
                'Arn': target_arn,
            },
        ]
    )

# 创建Lambda函数
def create_lambda_function(function_name, role_arn):
    response = lambda_client.create_function(
        FunctionName=function_name,
        Runtime='python3.8',
        Role=role_arn,
        Handler='lambda_function.lambda_handler',
        Code={
            'ZipFile': b'ZIP_FILE_CONTENTS'
        }
    )

# 示例用法
rule_name = 'api_change_notification_rule'
schedule_expression = 'cron(0 0 * * ? *)'  # 每天零点触发
target_arn = 'arn:aws:lambda:us-west-2:123456789012:function:api_change_notification_lambda'
create_event_rule(rule_name, schedule_expression, target_arn)

function_name = 'api_change_notification_lambda'
role_arn = 'arn:aws:iam::123456789012:role/lambda_execution_role'
create_lambda_function(function_name, role_arn)

以上是两种常用的AWS通知解决方法的示例代码。根据具体需求，您可以选择适合您的方式和服务。