下面是关于API保护的三种解决方法的代码示例：

1. JWT（JSON Web Token）：

import jwt

# 生成JWT token
payload = {'user_id': 1234}
secret_key = 'your_secret_key'
token = jwt.encode(payload, secret_key, algorithm='HS256')

# 验证JWT token
try:
    decoded_payload = jwt.decode(token, secret_key, algorithms=['HS256'])
    user_id = decoded_payload['user_id']
    print(f'Token verified. User ID: {user_id}')
except jwt.InvalidTokenError:
    print('Invalid token')

2. HMAC签名：

import hmac
import hashlib

# 生成HMAC签名
message = b'Hello, World!'
secret_key = b'your_secret_key'
signature = hmac.new(secret_key, message, hashlib.sha256).hexdigest()

# 验证HMAC签名
is_valid = hmac.compare_digest(signature, hmac.new(secret_key, message, hashlib.sha256).hexdigest())
if is_valid:
    print('Signature verified')
else:
    print('Invalid signature')

3. OAuth：

import requests

# 获取访问令牌
client_id = 'your_client_id'
client_secret = 'your_client_secret'
redirect_uri = 'your_redirect_uri'
authorization_code = 'your_authorization_code'

token_url = 'https://oauth.example.com/token'
data = {
    'grant_type': 'authorization_code',
    'client_id': client_id,
    'client_secret': client_secret,
    'redirect_uri': redirect_uri,
    'code': authorization_code
}
response = requests.post(token_url, data=data)
access_token = response.json()['access_token']

# 使用访问令牌访问受保护的API
api_url = 'https://api.example.com/protected_endpoint'
headers = {'Authorization': f'Bearer {access_token}'}
response = requests.get(api_url, headers=headers)
print(response.json())

请注意，以上代码示例仅为演示目的，并不是完整的实现。实际实现时，需要根据具体的需求和使用的编程语言进行适当的调整和扩展。