Handling the “httpresponsebase.__init__() got an unexpected keyword argument ‘mimetype’” Error in Django

When developing in Django, a common issue developers run into is the error httpresponsebase.__init__() got an unexpected keyword argument 'mimetype'. I encountered this problem firsthand while working on a project that involved sending custom responses from a Django view. 

This error can be a bit confusing, especially if you're used to older Django versions where mimetype was accepted as a parameter.

Here’s the journey I went through to understand and resolve the error.

The Initial Encounter

While building a custom file download view, I used HttpResponse to return the file response. Following some older code examples, I added mimetype to define the file type, something like:

response = HttpResponse(file_data, mimetype='application/pdf')

As soon as I ran the server and tested the endpoint, Django threw back the error:

TypeError: httpresponsebase.__init__() got an unexpected keyword argument 'mimetype'

It was a bit baffling at first. I knew mimetype was supported in earlier versions, so why was it causing issues now?

Researching the Error

To get a better understanding, I started researching. Several resources provided insights, and here's what I found:

• The mimetype Argument Has Been Deprecated: In newer Django versions (1.7+), the mimetype argument was replaced by content_type. This means that instead of using mimetype, I should be using content_type.
• Documentation Confirmation: The Django documentation confirmed that using content_type instead of mimetype was the correct approach going forward.

After learning about the change, I updated my code like this:

response = HttpResponse(file_data, content_type='application/pdf')

Once I made this change, the error disappeared, and the response worked as expected.

Possible Solutions for Different Scenarios

During my research, I came across several variations of this error, each with slightly different causes and solutions.

1. Using content_type Instead of mimetype in HttpResponse: The core solution, as explained, is to replace mimetype with content_type. This is applicable in almost any case where you’re defining the MIME type of a response in Django.
2. Checking Third-Party Packages: Sometimes, the error doesn’t come from your code directly but from third-party packages that haven’t updated to the new content_type parameter. In such cases, you might:
   • Look for Package Updates: Check if the package has an updated version that supports content_type instead of mimetype.
   • Edit the Source Code Locally: If the package hasn’t been updated, you may need to modify its code locally to replace mimetype with content_type. However, this approach is more of a temporary fix until an official update is released.
3. Errors in Custom Views Using pdfkit or xhtml2pdf: If you’re using libraries like pdfkit or xhtml2pdf to generate PDFs, you may encounter similar errors:
   • For instance, in xhtml2pdf, when rendering PDFs, use content_type='application/pdf' to avoid the mimetype issue.
   • Similarly, with pdfkit.from_string or pdfkit.from_url, ensure content_type is correctly set to avoid errors.

The error httpresponsebase.__init__() got an unexpected keyword argument 'mimetype' is due to the deprecation of the mimetype argument in Django’s HttpResponse and related classes. By replacing mimetype with content_type, you can ensure your code is compatible with newer versions of Django.