PUT请求Payload用本地文件报错：BufferedReader无法JSON序列化求助

你尝试向Printful API发送PUT请求，希望在Payload中包含本地PNG文件信息，使用open('images/path-to-image/image-1.png', 'rb')读取文件，但收到错误：

TypeError: Object of type BufferedReader is not JSON serializable

改用网络图片URL时代码可正常运行，需明确错误原因及本地文件的正确使用方式。

你的完整代码： #

order_number = 99
item_number = 12345678
url = f"https://api.printful.com/orders/@{order_number}"

payload={
'items': [
    {'external_id': str(item_number),
     'files': [
         {'url': open('images/path-to-image/image-1.png', 'rb'), 
          'position': {
              'area_width': 3000, 
              'area_height': 4000, 
              'width': 3000, 
              'height': 4000, 
              'top': 0, 
              'left': 0}
         }
     ]
    }
]
}
headers = {
'Authorization': 'Bearer PRIVATE-KEY'
}

response = requests.request("PUT", url, headers=headers, json=payload)
res = response.json()

print(f"Order {order_number}, Code result: {res['code']}")

错误原因 #

你直接将open()返回的BufferedReader文件流对象放入了JSON Payload中，但JSON仅支持序列化字符串、数字、列表、字典等基础数据类型，无法直接处理文件流对象，因此触发序列化错误。

解决方法 #

Printful API支持两种方式处理本地文件上传：

方式1：先上传文件到Printful存储，再使用返回的URL #

先调用Printful的文件上传API将本地图片上传至其服务器，获取返回的文件URL后，再将该URL放入PUT请求的Payload中：

import requests

# 1. 上传本地文件到Printful
upload_url = "https://api.printful.com/files"
headers = {'Authorization': 'Bearer PRIVATE-KEY'}
with open('images/path-to-image/image-1.png', 'rb') as img_file:
    files = {'file': img_file}
    upload_response = requests.post(upload_url, headers=headers, files=files)
upload_data = upload_response.json()
file_url = upload_data['result']['url']

# 2. 发送PUT请求更新订单
order_number = 99
item_number = 12345678
url = f"https://api.printful.com/orders/@{order_number}"

payload={
'items': [
    {'external_id': str(item_number),
     'files': [
         {'url': file_url, 
          'position': {
              'area_width': 3000, 
              'area_height': 4000, 
              'width': 3000, 
              'height': 4000, 
              'top': 0, 
              'left': 0}
         }
     ]
    }
]
}

response = requests.put(url, headers=headers, json=payload)
res = response.json()

print(f"Order {order_number}, Code result: {res['code']}")

方式2：使用multipart/form-data格式直接发送文件 #

无需单独调用上传API，将请求改为multipart/form-data格式，同时传递JSON数据和本地文件：

import requests
import json

order_number = 99
item_number = 12345678
url = f"https://api.printful.com/orders/@{order_number}"

# 定义订单Payload数据
payload_data = {
'items': [
    {'external_id': str(item_number),
     'files': [
         {'url': 'file://image-1.png',  # 用该标识关联上传的文件
          'position': {
              'area_width': 3000, 
              'area_height': 4000, 
              'width': 3000, 
              'height': 4000, 
              'top': 0, 
              'left': 0}
         }
     ]
    }
]
}

headers = {'Authorization': 'Bearer PRIVATE-KEY'}
# 组合multipart数据：JSON转字符串+本地文件
with open('images/path-to-image/image-1.png', 'rb') as img_file:
    multipart_data = {
        'json': (None, json.dumps(payload_data), 'application/json'),
        'image-1.png': img_file
    }
    response = requests.put(url, headers=headers, files=multipart_data)

res = response.json()
print(f"Order {order_number}, Code result: {res['code']}")

注意事项 #

• 使用with open(...) as f:的写法，可自动关闭文件流，避免资源泄漏
• 确保本地文件路径正确，避免触发文件找不到的异常
• 保持Authorization头部的密钥有效，否则会触发权限错误

内容的提问来源于stack exchange，提问作者Alex Capellan