Django后端用PIL处理上传图片时出现AttributeError报错

错误信息 #

<class 'AttributeError'> 347
'_io.BufferedRandom' object has no attribute 'getvalue'

相关代码 #

try:
  if 'image' in request.FILES['image'].content_type:
    image = request.FILES['image']

    image_name = profile["user"] + "." + image.name.split(".")[1]

    image_value = image.file.getvalue()

    with Image.open(image) as im:
      if (getattr(im, "is_animated", False)):
        if profile.premium:
          print("premium image posted")

          updated_profile['pfp'] = image_name 

          functions.upload_image("pfp", image_value, image_name)  
        else:
          print("premium error")

          messages.error(request, "You need premium for animated posts!")
      else:
        print("image posted")
        
        updated_profile['pfp'] = image_name

        functions.upload_image("pfp", image_value, image_name)
except Exception as e:
  exc_type, exc_obj, exc_tb = sys.exc_info()
  print(exc_type, exc_tb.tb_lineno)
  print(e)

报错原因 #

request.FILES['image'].file是_io.BufferedRandom类型的磁盘文件流，这个对象没有getvalue()方法——getvalue()是内存字节流BytesIO的专属方法。直接调用磁盘文件流的getvalue()，就会触发AttributeError。

解决方法 #

方法1：用read()读取内容并重置指针 #

直接调用read()读取文件内容，读取后必须将文件指针重置到开头，否则后续Image.open(image)会因为指针在文件末尾而读不到内容：

# 替换原来的image_value = image.file.getvalue()
image_value = image.file.read()
# 重置文件指针到起始位置
image.file.seek(0)

方法2：转成BytesIO处理 #

如果需要使用getvalue()，可以先将磁盘文件流转成内存中的BytesIO对象，同样要注意重置原文件指针：

from io import BytesIO

# 读取文件内容到BytesIO
image_bytes = BytesIO(image.file.read())
image_value = image_bytes.getvalue()
# 重置原文件指针，保证后续Image.open能正常读取
image.file.seek(0)

# 后续PIL打开可以用image_bytes或者原image对象
with Image.open(image_bytes) as im:
    # 原有处理逻辑不变

修改后的完整代码示例 #

try:
  if 'image' in request.FILES['image'].content_type:
    image = request.FILES['image']

    image_name = profile["user"] + "." + image.name.split(".")[1]

    # 替换报错的行，使用方法1实现
    image_value = image.file.read()
    image.file.seek(0)

    with Image.open(image) as im:
      if (getattr(im, "is_animated", False)):
        if profile.premium:
          print("premium image posted")

          updated_profile['pfp'] = image_name 

          functions.upload_image("pfp", image_value, image_name)  
        else:
          print("premium error")

          messages.error(request, "You need premium for animated posts!")
      else:
        print("image posted")
        
        updated_profile['pfp'] = image_name

        functions.upload_image("pfp", image_value, image_name)
except Exception as e:
  exc_type, exc_obj, exc_tb = sys.exc_info()
  print(exc_type, exc_tb.tb_lineno)
  print(e)

内容的提问来源于stack exchange，提问作者kipteam