Utilities

Utilities

Various utility functions shipped with Werkzeug.

HTML Helpers

class werkzeug.utils.HTMLBuilder(dialect)
Helper object for HTML generation.

Per default there are two instances of that class. The html one, andthe xhtml one for those two dialects. The class uses keyword parametersand positional parameters to generate small snippets of HTML.

Keyword parameters are converted to XML/SGML attributes, positionalarguments are used as children. Because Python accepts positionalarguments before keyword arguments it's a good idea to use a list with thestar-syntax for some children:

>>> html.p(class_='foo', *[html.a('foo', href='foo.html'), ' ',
...                        html.a('bar', href='bar.html')])
u'<p class="foo"><a href="foo.html">foo</a> <a href="bar.html">bar</a></p>'

This class works around some browser limitations and can not be used forarbitrary SGML/XML generation. For that purpose lxml and similarlibraries exist.

Calling the builder escapes the string passed:

>>> html.p(html("<foo>"))
u'<p>&lt;foo&gt;</p>'

werkzeug.utils.escape(s, quote=None)
Replace special characters “&”, “<”, “>” and (”) to HTML-safe sequences.

There is a special handling for None which escapes to an empty string.

在 0.9 版更改: quote is now implicitly on.

werkzeug.utils.unescape(s)
The reverse function of escape. This unescapes all the HTMLentities, not only the XML entities inserted by escape.

General Helpers

class werkzeug.utils.cached_property(func, name=None, doc=None)
A decorator that converts a function into a lazy property. Thefunction wrapped is called the first time to retrieve the resultand then that calculated result is used the next time you accessthe value:

class Foo(object):

    @cached_property
    def foo(self):
        # calculate something important here
        return 42

The class has to have a dict in order for this property towork.

class werkzeug.utils.environ_property(name, default=None, load_func=None, dump_func=None, read_only=None, doc=None)
Maps request attributes to environment variables. This works not onlyfor the Werzeug request object, but also any other class with anenviron attribute:

>>> class Test(object):
...     environ = {'key': 'value'}
...     test = environ_property('key')
>>> var = Test()
>>> var.test
'value'

If you pass it a second value it's used as default if the key does notexist, the third one can be a converter that takes a value and convertsit. If it raises ValueError [http://docs.python.org/dev/library/exceptions.html#ValueError] or TypeError [http://docs.python.org/dev/library/exceptions.html#TypeError] the default valueis used. If no default value is provided None is used.

Per default the property is read only. You have to explicitly enable itby passing read_only=False to the constructor.

class werkzeug.utils.header_property(name, default=None, load_func=None, dump_func=None, read_only=None, doc=None)
Like environ_property but for headers.

werkzeug.utils.parse_cookie(header, charset='utf-8', errors='replace', cls=None)
Parse a cookie. Either from a string or WSGI environ.

Per default encoding errors are ignored. If you want a different behavioryou can set errors to 'replace' or 'strict'. In strict mode aHTTPUnicodeError is raised.

在 0.5 版更改: This function now returns a TypeConversionDict instead of aregular dict. The cls parameter was added.

werkzeug.utils.dump_cookie(key, value='', max_age=None, expires=None, path='/', domain=None, secure=False, httponly=False, charset='utf-8', sync_expires=True)
Creates a new Set-Cookie header without the Set-Cookie prefixThe parameters are the same as in the cookie Morsel object in thePython standard library but it accepts unicode data, too.

On Python 3 the return value of this function will be a unicodestring, on Python 2 it will be a native string. In both cases thereturn value is usually restricted to ascii as the vast majority ofvalues are properly escaped, but that is no guarantee. If a unicodestring is returned it's tunneled through latin1 as required byPEP 3333.

The return value is not ASCII safe if the key contains unicodecharacters. This is technically against the specification buthappens in the wild. It's strongly recommended to not usenon-ASCII values for the keys.

werkzeug.utils.redirect(location, code=302)
Return a response object (a WSGI application) that, if called,redirects the client to the target location. Supported codes are 301,302, 303, 305, and 307. 300 is not supported because it's not a realredirect and 304 because it's the answer for a request with a requestwith defined If-Modified-Since headers.

0.6 新版功能: The location can now be a unicode string that is encoded usingthe iri_to_uri() function.

werkzeug.utils.append_slash_redirect(environ, code=301)
Redirect to the same URL but with a slash appended. The behaviorof this function is undefined if the path ends with a slash already.

werkzeug.utils.import_string(import_name, silent=False)
Imports an object based on a string. This is useful if you want touse import paths as endpoints or something similar. An import path canbe specified either in dotted notation (xml.sax.saxutils.escape)or with a colon as object delimiter (xml.sax.saxutils:escape).

If silent is True the return value will be None if the import fails.

werkzeug.utils.find_modules(import_path, include_packages=False, recursive=False)
Find all the modules below a package. This can be useful toautomatically import all views / controllers so that their metaclasses /function decorators have a chance to register themselves on theapplication.

Packages are not returned unless include_packages is True. This canalso recursively list modules but in that case it will import all thepackages to get the correct load path of that module.

werkzeug.utils.validate_arguments(func, args, kwargs, drop_extra=True)
Check if the function accepts the arguments and keyword arguments.Returns a new (args,kwargs) tuple that can safely be passed tothe function without causing a TypeError because the function signatureis incompatible. If drop_extra is set to True (which is the default)any extra positional or keyword arguments are dropped automatically.

The exception raised provides three attributes:

missingA set of argument names that the function expected but wheremissing.extraA dict of keyword arguments that the function can not handle butwhere provided.extra_positionalA list of values that where given by positional argument but thefunction cannot accept.
This can be useful for decorators that forward user submitted data toa view function:

from werkzeug.utils import ArgumentValidationError, validate_arguments

def sanitize(f):
    def proxy(request):
        data = request.values.to_dict()
        try:
            args, kwargs = validate_arguments(f, (request,), data)
        except ArgumentValidationError:
            raise BadRequest('The browser failed to transmit all '
                             'the data expected.')
        return f(*args, **kwargs)
    return proxy

werkzeug.utils.secure_filename(filename)
Pass it a filename and it will return a secure version of it. Thisfilename can then safely be stored on a regular file system and passedto os.path.join() [http://docs.python.org/dev/library/os.path.html#os.path.join]. The filename returned is an ASCII only stringfor maximum portability.

On windows system the function also makes sure that the file is notnamed after one of the special device files.

>>> secure_filename("My cool movie.mov")
'My_cool_movie.mov'
>>> secure_filename("../../../etc/passwd")
'etc_passwd'
>>> secure_filename(u'i contain cool \xfcml\xe4uts.txt')
'i_contain_cool_umlauts.txt'

The function might return an empty filename. It's your responsibilityto ensure that the filename is unique and that you generate randomfilename if the function returned an empty one.

0.5 新版功能.

werkzeug.utils.bind_arguments(func, args, kwargs)
Bind the arguments provided into a dict. When passed a function,a tuple of arguments and a dict of keyword arguments bind_argumentsreturns a dict of names as the function would see it. This can be usefulto implement a cache decorator that uses the function arguments to buildthe cache key based on the values of the arguments.

URL Helpers

class werkzeug.urls.Href(base='./', charset='utf-8', sort=False, key=None)
Implements a callable that constructs URLs with the given base. Thefunction can be called with any number of positional and keywordarguments which than are used to assemble the URL. Works with URLsand posix paths.

Positional arguments are appended as individual segments tothe path of the URL:

>>> href = Href('/foo')
>>> href('bar', 23)
'/foo/bar/23'
>>> href('foo', bar=23)
'/foo/foo?bar=23'

If any of the arguments (positional or keyword) evaluates to None itwill be skipped. If no keyword arguments are given the last argumentcan be a dict [http://docs.python.org/dev/library/stdtypes.html#dict] or MultiDict (or any other dict subclass),otherwise the keyword arguments are used for the query parameters, cuttingoff the first trailing underscore of the parameter name:

>>> href(is_=42)
'/foo?is=42'
>>> href({'foo': 'bar'})
'/foo?foo=bar'

Combining of both methods is not allowed:

>>> href({'foo': 'bar'}, bar=42)
Traceback (most recent call last):
  ...
TypeError: keyword arguments and query-dicts can't be combined

Accessing attributes on the href object creates a new href object withthe attribute name as prefix:

>>> bar_href = href.bar
>>> bar_href("blub")
'/foo/bar/blub'

If sort is set to True the items are sorted by key or the defaultsorting algorithm:

>>> href = Href("/", sort=True)
>>> href(a=1, b=2, c=3)
'/?a=1&b=2&c=3'

0.5 新版功能: sort and key were added.

werkzeug.urls.url_decode(s, charset='utf-8', decode_keys=False, include_empty=True, errors='replace', separator='&', cls=None)
Parse a querystring and return it as MultiDict. There is adifference in key decoding on different Python versions. On Python 3keys will always be fully decoded whereas on Python 2, keys willremain bytestrings if they fit into ASCII. On 2.x keys can be forcedto be unicode by setting decode_keys to True.

If the charset is set to None no unicode decoding will happen andraw bytes will be returned.

Per default a missing value for a key will default to an empty key. Ifyou don't want that behavior you can set include_empty to False.

Per default encoding errors are ignored. If you want a different behavioryou can set errors to 'replace' or 'strict'. In strict mode aHTTPUnicodeError is raised.

在 0.5 版更改: In previous versions ”;” and “&” could be used for url decoding.This changed in 0.5 where only “&” is supported. If you want touse ”;” instead a different separator can be provided.

The cls parameter was added.

werkzeug.urls.url_decode_stream(stream, charset='utf-8', decode_keys=False, include_empty=True, errors='replace', separator='&', cls=None, limit=None, return_iterator=False)
Works like url_decode() but decodes a stream. The behaviorof stream and limit follows functions likemake_line_iter(). The generator of pairs isdirectly fed to the cls so you can consume the data while it'sparsed.

0.8 新版功能.

werkzeug.urls.url_encode(obj, charset='utf-8', encode_keys=False, sort=False, key=None, separator='&')
URL encode a dict/MultiDict. If a value is None it will not appearin the result string. Per default only values are encoded into the targetcharset strings. If encode_keys is set to True unicode keys aresupported too.

If sort is set to True the items are sorted by key or the defaultsorting algorithm.

0.5 新版功能: sort, key, and separator were added.

werkzeug.urls.url_encode_stream(obj, stream=None, charset='utf-8', encode_keys=False, sort=False, key=None, separator='&')
Like url_encode() but writes the results to a streamobject. If the stream is None a generator over all encodedpairs is returned.

0.8 新版功能.

werkzeug.urls.url_quote(string, charset='utf-8', errors='strict', safe='/:', unsafe='')
URL encode a single string with a given encoding.

0.9.2 新版功能: The unsafe parameter was added.

werkzeug.urls.url_quote_plus(string, charset='utf-8', errors='strict', safe='')
URL encode a single string with the given encoding and convertwhitespace to “+”.

werkzeug.urls.url_unquote(string, charset='utf-8', errors='replace', unsafe='')
URL decode a single string with a given encoding. If the charsetis set to None no unicode decoding is performed and raw bytesare returned.

werkzeug.urls.url_unquote_plus(s, charset='utf-8', errors='replace')
URL decode a single string with the given charset and decode “+” towhitespace.

Per default encoding errors are ignored. If you want a different behavioryou can set errors to 'replace' or 'strict'. In strict mode aHTTPUnicodeError is raised.

werkzeug.urls.url_fix(s, charset='utf-8')
Sometimes you get an URL by a user that just isn't a real URL becauseit contains unsafe characters like ‘ ‘ and so on. This function can fixsome of the problems in a similar way browsers handle data entered by theuser:

>>> url_fix(u'http://de.wikipedia.org/wiki/Elf (Begriffskl\xe4rung)')
'http://de.wikipedia.org/wiki/Elf%20(Begriffskl%C3%A4rung)'

werkzeug.urls.uri_to_iri(uri, charset='utf-8', errors='replace')
Converts a URI in a given charset to a IRI.

Examples for URI versus IRI:

>>> uri_to_iri(b'http://xn--n3h.net/')
u'http://\u2603.net/'
>>> uri_to_iri(b'http://%C3%BCser:p%C3%A4ssword@xn--n3h.net/p%C3%A5th')
u'http://\xfcser:p\xe4ssword@\u2603.net/p\xe5th'

Query strings are left unchanged:

>>> uri_to_iri('/?foo=24&x=%26%2f')
u'/?foo=24&x=%26%2f'

0.6 新版功能.

werkzeug.urls.iri_to_uri(iri, charset='utf-8', errors='strict')
Converts any unicode based IRI to an acceptable ASCII URI. Werkzeug alwaysuses utf-8 URLs internally because this is what browsers and HTTP do aswell. In some places where it accepts an URL it also accepts a unicode IRIand converts it into a URI.

Examples for IRI versus URI:

>>> iri_to_uri(u'http://?.net/')
'http://xn--n3h.net/'
>>> iri_to_uri(u'http://üser:p?ssword@?.net/p?th')
'http://%C3%BCser:p%C3%A4ssword@xn--n3h.net/p%C3%A5th'

0.6 新版功能.

UserAgent Parsing

class werkzeug.useragents.UserAgent(environ_or_string)
Represents a user agent. Pass it a WSGI environment or a user agentstring and you can inspect some of the details from the user agentstring via the attributes. The following attributes exist:

string