Django rest framework  authentication error “ TypeError: 'type' object is not iterable ”

This error comes because "authentication_classes" expecting an iterable(list/tuple) but somehow it is getting something else. So it needs to check a few things to resolve this issue.

File "/usr/local/lib/python3.7/site-packages/django/core/handlers/exception.py", line 47, in inner
    response = get_response(request)
  File "/usr/local/lib/python3.7/site-packages/django/core/handlers/base.py", line 181, in _get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/views/decorators/csrf.py", line 54, in wrapped_view
    return view_func(*args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/django/views/generic/base.py", line 70, in view
    return self.dispatch(request, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/rest_framework/views.py", line 492, in dispatch
    request = self.initialize_request(request, *args, **kwargs)
  File "/usr/local/lib/python3.7/site-packages/rest_framework/views.py", line 394, in initialize_request
    authenticators=self.get_authenticators(),
  File "/usr/local/lib/python3.7/site-packages/rest_framework/views.py", line 272, in get_authenticators
    return [auth() for auth in self.authentication_classes]
TypeError: 'type' object is not iterable

authentication scheme with multiple classes

authentication scheme in setting file

# List
REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': [
        'rest_framework.authentication.BasicAuthentication',
        'rest_framework.authentication.SessionAuthentication',
    ]
}

# OR

# Tuple
REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework.authentication.BasicAuthentication',
        'rest_framework.authentication.SessionAuthentication',
    )
}

per-view or per-viewset basis

# authentication_classes defined in List
authentication_classes = [SessionAuthentication, BasicAuthentication]
   
# OR

# authentication_classes defined in Tuple
authentication_classes = (SessionAuthentication, BasicAuthentication)

authentication scheme with a single class

if you are using only one authentication class then with the tuple assignment put a "comma" at the end otherwise the value is treated as a string which raised the error "TypeError: 'type' object is not iterable"

# Tuple | notice that after 'rest_framework_jwt.authentication.JSONWebTokenAuthentication' 
# there is a "," comma
REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': (
        'rest_framework_jwt.authentication.JSONWebTokenAuthentication',
    ),
}

# OR

# List | comma can be ignored
REST_FRAMEWORK = {
    'DEFAULT_AUTHENTICATION_CLASSES': [
        'rest_framework_jwt.authentication.JSONWebTokenAuthentication'
    ],
}

per-view or per-viewset basis

# Tuple | notice that after 'authentication.TokenAuthentication' there is a "," comma
authentication_classes = (authentication.TokenAuthentication,)
   
# OR

# List | comma can be ignored
authentication_classes = [authentication.TokenAuthentication]