Differences Between WebOb and Other Systems — WebOb 1.4.1 documentation

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# Differences Between WebOb and Other Systems

This document points out some of the API differences between the Request and Response object, and the objects in other systems.

Contents

- Differences Between WebOb and Other Systems
  - paste.wsgiwrappers and Pylons
    - Request
    - Response
  - Django
    - Request
    - QueryDict
    - Response
    - Response Subclasses
  - CherryPy/TurboGears
    - Request
    - Response
  - Yaro
    - Request
  - Werkzeug
    - Request
    - Response
  - Zope 3
    - Request
    - Response
  - mod_python
    - Request
    - Response
  - webapp Response
  - PHP
    - `$_POST`, `$_GET`, `$_FILES`
    - `$_COOKIES`
    - `$_SERVER`, `$_REQUEST`, `$_ENV`
    - `$HTTP_RAW_POST_DATA`
    - The response

## paste.wsgiwrappers and Pylons

The Pylons `request` and `response` object are based on `paste.wsgiwrappers.WSGIRequest` and `WSGIResponse`

There is no concept of `defaults` in WebOb. In Paste/Pylons these serve as threadlocal settings that control certain policies on the request and response object. In WebOb you should make your own subclasses to control policy (though in many ways simply being explicit elsewhere removes the need for this policy).

### Request

`body`:
  This is a file-like object in WSGIRequest. In WebOb it is a string (to match Response.body) and the file-like object is available through `req.body_file`
`languages()`:
  This is available through `req.accept_language`, particularly `req.accept_language.best_matches(fallback_language)`
`match_accept(mimetypes)`:
  This is available through `req.accept.first_match(mimetypes)`; or if you trust the client’s quality ratings, you can use `req.accept.best_match(mimetypes)`
`errors`:
  This controls how unicode decode errors are handled; it is now named `unicode_errors`

There are also many extra methods and attributes on WebOb Request objects.

### Response

`determine_charset()`:
  Is now available as `res.charset`
`has_header(header)`:
  Should be done with `header in res.headers`
`get_content()` and `wsgi_response()`:
  These are gone; you should use `res.body` or `res(environ, start_response)`
`write(content)`:
  Available in `res.body_file.write(content)`.
`flush()` and `tell()`:
  Not available.

There are also many extra methods and attributes on WebOb Response objects.

## Django

This is a quick summary from reading the Django documentation.

### Request

`encoding`:
  Is `req.charset`
`REQUEST`:
  Is `req.params`
`FILES`:
  File uploads are `cgi.FieldStorage` objects directly in `res.POST`
`META`:
  Is `req.environ`
`user`:
  No equivalent (too connected to application model for WebOb). There is `req.remote_user`, which is only ever a string.
`session`:
  No equivalent
`raw_post_data`:
  Available with `req.body`
`__getitem__(key)`:
  You have to use `req.params`
`is_secure()`:
  No equivalent; you could use `req.scheme == 'https'`.

### QueryDict

QueryDict is the way Django represents the multi-key dictionary-like objects that are request variables (query string and POST body variables). The equivalent in WebOb is MultiDict.

Mutability:
  WebOb dictionaries are sometimes mutable (req.GET is, req.params is not)
Ordering:
  I believe Django does not order the keys fully; MultiDict is a full ordering. Methods that iterate over the parameters iterate over keys in their order in the original request.
`keys()`, `items()`, `values()` (plus `iter*`):
  These return all values in MultiDict, but only the last value for a QueryDict. That is, given `a=1&a=2` with MultiDict `d.items()` returns `[('a', '1'), ('a', '2')]`, but QueryDict returns `[('a', '1')]`
`getlist(key)`:
  Available as `d.getall(key)`
`setlist(key)`:
  No direct equivalent
`appendlist(key, value)`:
  Available as `d.add(key, value)`
`setlistdefault(key, default_list)`:
  No direct equivalent
`lists()`:
  Is `d.dict_of_lists()`

The MultiDict object has a `d.getone(key)` method, that raises KeyError if there is not exactly one key. There is a method `d.mixed()` which returns a version where values are lists if there are multiple values for a list. This is similar to how many cgi-based request forms are represented.

### Response

Constructor:
  Somewhat different. WebOb takes any keyword arguments as attribute assignments. Django only takes a couple arguments. The `mimetype` argument is `content_type`, and `content_type` is the entire `Content-Type` header (including charset).
dictionary-like:
  The Django response object is somewhat dictionary-like, setting headers. The equivalent dictionary-like object is `res.headers`. In WebOb this is a MultiDict.
`has_header(header)`:
  Use `header in res.headers`
`flush()`, `tell()`:
  Not available
`content`:
  Use `res.body` for the `str` value, `res.unicode_body` for the `unicode` value

### Response Subclasses

These are generally like `webob.exc` objects. `HttpResponseNotModified` is `HTTPNotModified`; this naming translation generally works.

## CherryPy/TurboGears

The CherryPy request object is also used by TurboGears 1.x.

### Request

`app`:
  No equivalent
`base`:
  `req.application_url`
`close()`:
  No equivalent
`closed`:
  No equivalent
`config`:
  No equivalent
`cookie`:
  A `SimpleCookie` object in CherryPy; a dictionary in WebOb (`SimpleCookie` can represent cookie parameters, but cookie parameters are only sent with responses not requests)
`dispatch`:
  No equivalent (this is the object dispatcher in CherryPy).
`error_page`, `error_response`, `handle_error`:
  No equivalent
`get_resource()`:
  Similar to `req.get_response(app)`
`handler`:
  No equivalent
`headers`, `header_list`:
  The WSGI environment represents headers as a dictionary, available through `req.headers` (no list form is available in the request).
`hooks`:
  No equivalent
`local`:
  No equivalent
`methods_with_bodies`:
  This represents methods where CherryPy will automatically try to read the request body. WebOb lazily reads POST requests with the correct content type, and no other bodies.
`namespaces`:
  No equivalent
`protocol`:
  As `req.environ['SERVER_PROTOCOL']`
`query_string`:
  As `req.query_string`
`remote`:
  `remote.ip` is like `req.remote_addr`. `remote.port` is not available. `remote.name` is in `req.environ.get('REMOTE_HOST')`
`request_line`:
  No equivalent
`respond()`:
  A method that is somewhat similar to `req.get_response()`.
`rfile`:
  `req.body_file`
`run`:
  No equivalent
`server_protocol`:
  As `req.environ['SERVER_PROTOCOL']`
`show_tracebacks`:
  No equivalent
`throw_errors`:
  No equivalent
`throws`:
  No equivalent
`toolmaps`:
  No equivalent
`wsgi_environ`:
  As `req.environ`

### Response

From information from the wiki.

`body`:
  This is an iterable in CherryPy, a string in WebOb; `res.app_iter` gives an iterable in WebOb.
`check_timeout`:
  No equivalent
`collapse_body()`:
  This turns a stream/iterator body into a single string. Accessing `res.body` will do this automatically.
`cookie`:
  Accessible through `res.set_cookie(...)`, `res.delete_cookie`, `res.unset_cookie()`
`finalize()`:
  No equivalent
`header_list`:
  In `res.headerlist`
`stream`:
  This can make CherryPy stream the response body out directory. There is direct no equivalent; you can use a dynamically generated iterator to do something similar.
`time`:
  No equivalent
`timed_out`:
  No equivalent

## Yaro

Yaro is a small wrapper around the WSGI environment, much like WebOb in scope.

The WebOb objects have many more methods and attributes. The Yaro Response object is a much smaller subset of WebOb’s Response.

### Request

`query`:
  As `req.GET`
`form`:
  As `req.POST`
`cookie`:
  A `SimpleCookie` object in Yaro; a dictionary in WebOb (`SimpleCookie` can represent cookie parameters, but cookie parameters are only sent with responses not requests)
`uri`:
  Returns a URI object, no equivalent (only string URIs available).
`redirect`:
  Not available (response-related). `webob.exc.HTTPFound()` can be useful here.
`forward(yaroapp)`, `wsgi_forward(wsgiapp)`:
  Available with `req.get_response(app)` and `req.call_application(app)`. In both cases it is a WSGI application in WebOb, there is no special kind of communication; `req.call_application()` just returns a `webob.Response` object.
`res`:
  The request object in WebOb may have a `req.response` attribute.

## Werkzeug

An offshoot of Pocoo, this library is based around WSGI, similar to Paste and Yaro.

This is taken from the wrapper documentation.

### Request

path:
  As `req.path_info`
args:
  As `req.GET`
form:
  As `req.POST`
values:
  As `req.params`
files:
  In `req.POST` (as FieldStorage objects)
data:
  In `req.body_file`

### Response

response:
  In `res.body` (settable as `res.body` or `res.app_iter`)
status:
  In `res.status_code`
mimetype:
  In `res.content_type`

## Zope 3

From the Zope 3 interfaces for the Request and Response.

### Request

`locale`, `setupLocale()`:
  This is not fully calculated, but information is available in `req.accept_languages`.
`principal`, `setPrincipal(principal)`:
  `req.remote_user` gives the username, but there is no standard place for a user object.
`publication`, `setPublication()`,
  These are associated with the object publishing system in Zope. This kind of publishing system is outside the scope of WebOb.
`traverse(object)`, `getTraversalStack()`, `setTraversalStack()`:
  These all relate to traversal, which is part of the publishing system.
`processInputs()`, `setPathSuffix(steps)`:
  Also associated with traversal and preparing the request.
`environment`:
  In `req.environ`
`bodyStream`:
  In `req.body_file`
`interaction`:
  This is the security context for the request; all the possible participants or principals in the request. There’s no equivalent.
`annotations`:
  Extra information associated with the request. This would generally go in custom keys of `req.environ`, or if you set attributes those attributes are stored in `req.environ['webob.adhoc_attrs']`.
`debug`:
  There is no standard debug flag for WebOb.
`__getitem__(key)`, `get(key)`, etc:
  These treat the request like a dictionary, which WebOb does not do. They seem to take values from the environment, not parameters. Also on the Zope request object is `items()`, `__contains__(key)`, `__iter__()`, `keys()`, `__len__()`, `values()`.
`getPositionalArguments()`:
  I’m not sure what the equivalent would be, as there are no positional arguments during instantiation (it doesn’t fit into WSGI). Maybe `wsgiorg.urlvars`?
`retry()`, `supportsRetry()`:
  Creates a new request that can be used to retry a request. Similar to `req.copy()`.
`close()`, `hold(obj)`:
  This closes resources associated with the request, including any “held” objects. There’s nothing similar.

### Response

`authUser`:
  Not sure what this is or does.
`reset()`:
  No direct equivalent; you’d have to do `res.headers = []; res.body = ''; res.status = 200`
`setCookie(name, value, **kw)`:
  Is `res.set_cookie(...)`.
`getCookie(name)`:
  No equivalent. Hm.
`expireCookie(name)`:
  Is `res.delete_cookie(name)`.
`appendToCookie(name, value)`:
  This appends the value to any existing cookie (separating values with a colon). WebOb does not do this.
`setStatus(status)`:
  Availble by setting `res.status` (can be set to an integer or a string of “code reason”).
`getHeader(name, default=None)`:
  Is `res.headers.get(name)`.
`getStatus()`:
  Is `res.status_code` (or `res.status` to include reason)
`addHeader(name, value)`:
  Is `res.headers.add(name, value)` (in Zope and WebOb, this does not clobber any previous value).
`getHeaders()`:
  Is `res.headerlist`.
`setHeader(name, value)`:
  Is `res.headers[name] = value`.
`getStatusString()`:
  Is `res.status`.
`consumeBody()`:
  This consumes any non-string body to turn the body into a single string. Any access to `res.body` will do this (e.g., when you have set the `res.app_iter`).
`internalError()`:
  This is available with `webob.exc.HTTP*()`.
`handleException(exc_info)`:
  This is provided with a tool like `paste.exceptions`.
`consumeBodyIter()`:
  This returns the iterable for the body, even if the body was a string. Anytime you access `res.app_iter` you will get an iterable. `res.body` and `res.app_iter` can be interchanged and accessed as many times as you want, unlike the Zope equivalents.
`setResult(result)`:

  You can achieve the same thing through `res.body = result`, or `res.app_iter = result`. `res.body` accepts None, a unicode string (if you have set a charset) or a normal string. `res.app_iter` only accepts None and an interable. You can’t update all of a response with one call.

  Like in Zope, WebOb updates Content-Length. Unlike Zope, it does not automatically calculate a charset.

## mod_python

Some key attributes from the mod_python request object.

### Request

`req.uri`:
  In `req.path`.
`req.user`:
  In `req.remote_user`.
`req.get_remote_host()`:
  In `req.environ['REMOTE_ADDR']` or `req.remote_addr`.
`req.headers_in.get('referer')`:
  In `req.headers.get('referer')` or `req.referer` (same pattern for other request headers, presumably).

### Response

`util.redirect` or `req.status = apache.HTTP_MOVED_TEMPORARILY`:

    from webob.exc import HTTPTemporaryRedirect
    exc = HTTPTemporaryRedirect(location=url)
    return exc(environ, start_response)

`req.content_type = "application/x-csv"` and `req.headers_out.add('Content-Disposition', 'attachment;filename=somefile.csv')`:

    res = req.ResponseClass()
    res.content_type = 'application/x-csv'
    res.headers.add('Content-Disposition', 'attachment;filename=somefile.csv')
    return res(environ, start_response)

## webapp Response

The Google App Engine webapp framework uses the WebOb Request object, but does not use its Response object.

The constructor for `webapp.Response` does not take any arguments. The response is created by the framework, so you don’t use it like `return Response(...)`, instead you use `self.response`. Also the response object automatically has `Cache-Control: no-cache` set, while the WebOb response does not set any cache headers.

`resp.set_status(code, message=None)`:
  This is handled by setting the `resp.status` attribute.
`resp.clear()`:
  You’d do `resp.body = ""`
`resp.wsgi_write(start_response)`:
  This writes the response using the `start_response` callback, and using the `start_response` writer. The WebOb response object is called as a WSGI app (`resp(environ, start_response)`) to do the equivalent.
`resp.out.write(text)`:
  This writes to an internal `StringIO` instance of the response. This uses the ability of the standard StringIO object to hold either unicode or `str` text, and so long as you are always consistent it will encode your content (but it does not respect your preferred encoding, it always uses UTF-8). The WebOb method `resp.write(text)` is basically equivalent, and also accepts unicode (using `resp.charset` for the encoding). You can also write to `resp.body_file`, but it does not allow unicode.

Besides exposing a `.headers` attribute (based on wsgiref.headers.Headers) there is no other API for the webapp response object. This means the response lacks:

- A usefully readable body or status.
- A useful constructor that makes it easy to treat responses like objects.
- Providing a non-string `app_iter` for the body (like a generator).
- Parsing of the Content-Type charset.
- Getter/setters for parsed forms of headers, specifically cache_control and last_modified.
- The `cache_expires` method
- `set_cookie`, `delete_cookie`, and `unset_cookie`. Instead you have to simply manually set the Set-Cookie header.
- `encode_content` and `decode_content` for handling gzip encoding.
- `md5_etag()` for generating an etag from the body.
- Conditional responses that will return 304 based on the response and request headers.
- The ability to serve Range request automatically.

## PHP

PHP does not have anything really resembling a request and response object. Instead these are encoded in a set of global objects for the request and functions for the response.

### `$_POST`, `$_GET`, `$_FILES`

These represent `req.POST` and `req.GET`.

PHP uses the variable names to tell whether a variable can hold multiple values. For instance `$_POST['name[]']`, which will be an array. In WebOb any variable can have multiple values, and you can get these through `req.POST.getall('name')`.

The files in `$_FILES` are simply in `req.POST` in WebOb, as FieldStorage instances.

### `$_COOKIES`

This is in `req.cookies`.

### `$_SERVER`, `$_REQUEST`, `$_ENV`

These are all in `req.environ`. These are not split up like they are in PHP, it’s all just one dictionary. Everything that would typically be in `$_ENV` is technically optional, and outside of a couple CGI-standard keys in `$_SERVER` most of those are also optional, but it is common for WSGI servers to populate the request with similar information as PHP.

### `$HTTP_RAW_POST_DATA`

This contains the unparsed data in the request body. This is in `req.body`.

### The response

Response headers in PHP are sent with `header("Header-Name: value")`. In WebOb there is a dictionary in `resp.headers` that can have values set; the headers aren’t actually sent until you send the response. You can add headers without overwriting (the equivalent of `header("...", false)`) with `resp.headers.add('Header-Name', 'value')`.

The status in PHP is sent with `http_send_status(code)`. In WebOb this is `resp.status = code`.

The body in PHP is sent implicitly through the rendering of the PHP body (or with `echo` or any other functions that send output).

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