Data Structures¶
Werkzeug provides some subclasses of common Python objects to extend them with additional features. Some of them are used to make them immutable, others are used to change some semantics to better work with HTTP.
General Purpose¶
Changed in version 0.6: The general purpose classes are now pickleable in each protocol as long
as the contained objects are pickleable. This means that the
FileMultiDict
won’t be pickleable as soon as it contains a
file.
-
class
werkzeug.datastructures.
TypeConversionDict
¶ Works like a regular dict but the
get()
method can perform type conversions.MultiDict
andCombinedMultiDict
are subclasses of this class and provide the same feature.New in version 0.5.
-
get
(key, default=None, type=None)¶ Return the default value if the requested data doesn’t exist. If type is provided and is a callable it should convert the value, return it or raise a
ValueError
if that is not possible. In this case the function will return the default as if the value was not found:>>> d = TypeConversionDict(foo='42', bar='blub') >>> d.get('foo', type=int) 42 >>> d.get('bar', -1, type=int) -1
Parameters: - key – The key to be looked up.
- default – The default value to be returned if the key can’t be looked up. If not further specified None is returned.
- type – A callable that is used to cast the value in the
MultiDict
. If aValueError
is raised by this callable the default value is returned.
-
-
class
werkzeug.datastructures.
ImmutableTypeConversionDict
¶ Works like a
TypeConversionDict
but does not support modifications.New in version 0.5.
-
class
werkzeug.datastructures.
MultiDict
(mapping=None)¶ A
MultiDict
is a dictionary subclass customized to deal with multiple values for the same key which is for example used by the parsing functions in the wrappers. This is necessary because some HTML form elements pass multiple values for the same key.MultiDict
implements all standard dictionary methods. Internally, it saves all values for a key as a list, but the standard dict access methods will only return the first value for a key. If you want to gain access to the other values, too, you have to use the list methods as explained below.Basic Usage:
>>> d = MultiDict([('a', 'b'), ('a', 'c')]) >>> d MultiDict([('a', 'b'), ('a', 'c')]) >>> d['a'] 'b' >>> d.getlist('a') ['b', 'c'] >>> 'a' in d True
It behaves like a normal dict thus all dict functions will only return the first value when multiple values for one key are found.
From Werkzeug 0.3 onwards, the KeyError raised by this class is also a subclass of the
BadRequest
HTTP exception and will render a page for a400 BAD REQUEST
if caught in a catch-all for HTTP exceptions.A
MultiDict
can be constructed from an iterable of(key, value)
tuples, a dict, aMultiDict
or from Werkzeug 0.2 onwards some keyword parameters.Parameters: mapping – the initial value for the MultiDict
. Either a regular dict, an iterable of(key, value)
tuples or None.-
add
(key, value)¶ Adds a new value for the key.
New in version 0.6.
Parameters: - key – the key for the value.
- value – the value to add.
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clear
() → None. Remove all items from D.¶
-
copy
()¶ Return a shallow copy of this object.
-
deepcopy
(memo=None)¶ Return a deep copy of this object.
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fromkeys
(S[, v]) → New dict with keys from S and values equal to v.¶ v defaults to None.
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get
(key, default=None, type=None)¶ Return the default value if the requested data doesn’t exist. If type is provided and is a callable it should convert the value, return it or raise a
ValueError
if that is not possible. In this case the function will return the default as if the value was not found:>>> d = TypeConversionDict(foo='42', bar='blub') >>> d.get('foo', type=int) 42 >>> d.get('bar', -1, type=int) -1
Parameters: - key – The key to be looked up.
- default – The default value to be returned if the key can’t be looked up. If not further specified None is returned.
- type – A callable that is used to cast the value in the
MultiDict
. If aValueError
is raised by this callable the default value is returned.
-
getlist
(key, type=None)¶ Return the list of items for a given key. If that key is not in the MultiDict, the return value will be an empty list. Just as get getlist accepts a type parameter. All items will be converted with the callable defined there.
Parameters: - key – The key to be looked up.
- type – A callable that is used to cast the value in the
MultiDict
. If aValueError
is raised by this callable the value will be removed from the list.
Returns: a
list
of all the values for the key.
-
has_key
(k) → True if D has a key k, else False¶
-
items
(*a, **kw)¶ Like
iteritems()
, but returns a list.
-
iteritems
(multi=False)¶ Return an iterator of
(key, value)
pairs.Parameters: multi – If set to True the iterator returned will have a pair for each value of each key. Otherwise it will only contain pairs for the first value of each key.
-
iterlists
()¶ Return a list of
(key, values)
pairs, where values is the list of all values associated with the key.
-
iterlistvalues
()¶ Return an iterator of all values associated with a key. Zipping
keys()
and this is the same as callinglists()
:>>> d = MultiDict({"foo": [1, 2, 3]}) >>> zip(d.keys(), d.listvalues()) == d.lists() True
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itervalues
()¶ Returns an iterator of the first value on every key’s value list.
-
keys
(*a, **kw)¶ Like
iterkeys()
, but returns a list.
-
lists
(*a, **kw)¶ Like
iterlists()
, but returns a list.
-
listvalues
(*a, **kw)¶ Like
iterlistvalues()
, but returns a list.
-
pop
(key, default=no value)¶ Pop the first item for a list on the dict. Afterwards the key is removed from the dict, so additional values are discarded:
>>> d = MultiDict({"foo": [1, 2, 3]}) >>> d.pop("foo") 1 >>> "foo" in d False
Parameters: - key – the key to pop.
- default – if provided the value to return if the key was not in the dictionary.
-
popitem
()¶ Pop an item from the dict.
-
popitemlist
()¶ Pop a
(key, list)
tuple from the dict.
-
poplist
(key)¶ Pop the list for a key from the dict. If the key is not in the dict an empty list is returned.
Changed in version 0.5: If the key does no longer exist a list is returned instead of raising an error.
-
setdefault
(key, default=None)¶ Returns the value for the key if it is in the dict, otherwise it returns default and sets that value for key.
Parameters: - key – The key to be looked up.
- default – The default value to be returned if the key is not in the dict. If not further specified it’s None.
-
setlist
(key, new_list)¶ Remove the old values for a key and add new ones. Note that the list you pass the values in will be shallow-copied before it is inserted in the dictionary.
>>> d = MultiDict() >>> d.setlist('foo', ['1', '2']) >>> d['foo'] '1' >>> d.getlist('foo') ['1', '2']
Parameters: - key – The key for which the values are set.
- new_list – An iterable with the new values for the key. Old values are removed first.
-
setlistdefault
(key, default_list=None)¶ Like setdefault but sets multiple values. The list returned is not a copy, but the list that is actually used internally. This means that you can put new values into the dict by appending items to the list:
>>> d = MultiDict({"foo": 1}) >>> d.setlistdefault("foo").extend([2, 3]) >>> d.getlist("foo") [1, 2, 3]
Parameters: - key – The key to be looked up.
- default – An iterable of default values. It is either copied (in case it was a list) or converted into a list before returned.
Returns: a
list
-
to_dict
(flat=True)¶ Return the contents as regular dict. If flat is True the returned dict will only have the first item present, if flat is False all values will be returned as lists.
Parameters: flat – If set to False the dict returned will have lists with all the values in it. Otherwise it will only contain the first value for each key. Returns: a dict
-
update
(other_dict)¶ update() extends rather than replaces existing key lists.
-
values
(*a, **kw)¶ Like
itervalues()
, but returns a list.
-
viewitems
() → a set-like object providing a view on D's items¶
-
viewkeys
() → a set-like object providing a view on D's keys¶
-
viewvalues
() → an object providing a view on D's values¶
-
-
class
werkzeug.datastructures.
OrderedMultiDict
(mapping=None)¶ Works like a regular
MultiDict
but preserves the order of the fields. To convert the ordered multi dict into a list you can use theitems()
method and pass itmulti=True
.In general an
OrderedMultiDict
is an order of magnitude slower than aMultiDict
.note
Due to a limitation in Python you cannot convert an ordered multi dict into a regular dict by using
dict(multidict)
. Instead you have to use theto_dict()
method, otherwise the internal bucket objects are exposed.
-
class
werkzeug.datastructures.
ImmutableMultiDict
(mapping=None)¶ An immutable
MultiDict
.New in version 0.5.
-
class
werkzeug.datastructures.
ImmutableOrderedMultiDict
(mapping=None)¶ An immutable
OrderedMultiDict
.New in version 0.6.
-
class
werkzeug.datastructures.
CombinedMultiDict
(dicts=None)¶ A read only
MultiDict
that you can pass multipleMultiDict
instances as sequence and it will combine the return values of all wrapped dicts:>>> from werkzeug.datastructures import CombinedMultiDict, MultiDict >>> post = MultiDict([('foo', 'bar')]) >>> get = MultiDict([('blub', 'blah')]) >>> combined = CombinedMultiDict([get, post]) >>> combined['foo'] 'bar' >>> combined['blub'] 'blah'
This works for all read operations and will raise a TypeError for methods that usually change data which isn’t possible.
From Werkzeug 0.3 onwards, the KeyError raised by this class is also a subclass of the
BadRequest
HTTP exception and will render a page for a400 BAD REQUEST
if caught in a catch-all for HTTP exceptions.
-
class
werkzeug.datastructures.
FileMultiDict
(mapping=None)¶ A special
MultiDict
that has convenience methods to add files to it. This is used forEnvironBuilder
and generally useful for unittesting.New in version 0.5.
-
add_file
(name, file, filename=None, content_type=None)¶ Adds a new file to the dict. file can be a file name or a
file
-like or aFileStorage
object.Parameters: - name – the name of the field.
- file – a filename or
file
-like object - filename – an optional filename
- content_type – an optional content type
-
Others¶
-
class
werkzeug.datastructures.
FileStorage
(stream=None, filename=None, name=None, content_type=None, content_length=None, headers=None)¶ The
FileStorage
class is a thin wrapper over incoming files. It is used by the request object to represent uploaded files. All the attributes of the wrapper stream are proxied by the file storage so it’s possible to dostorage.read()
instead of the long formstorage.stream.read()
.-
stream
¶ The input stream for the uploaded file. This usually points to an open temporary file.
-
filename
¶ The filename of the file on the client.
-
name
¶ The name of the form field.
-
headers
¶ The multipart headers as
Headers
object. This usually contains irrelevant information but in combination with custom multipart requests the raw headers might be interesting.New in version 0.6.
-
close
()¶ Close the underlying file if possible.
-
content_length
¶ The content-length sent in the header. Usually not available
-
content_type
¶ The content-type sent in the header. Usually not available
-
mimetype
¶ Like
content_type
but without parameters (eg, without charset, type etc.). For example if the content type istext/html; charset=utf-8
the mimetype would be'text/html'
.New in version 0.7.
-
mimetype_params
¶ The mimetype parameters as dict. For example if the content type is
text/html; charset=utf-8
the params would be{'charset': 'utf-8'}
.New in version 0.7.
-
save
(dst, buffer_size=16384)¶ Save the file to a destination path or file object. If the destination is a file object you have to close it yourself after the call. The buffer size is the number of bytes held in memory during the copy process. It defaults to 16KB.
For secure file saving also have a look at
secure_filename()
.Parameters: - dst – a filename or open file object the uploaded file is saved to.
- buffer_size – the size of the buffer. This works the same as
the length parameter of
shutil.copyfileobj()
.
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