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
Changelog
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.
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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.Changelog
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 aValueError
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.Changelog
New in version 0.5.
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class werkzeug.datastructures.MultiDict(mapping=None)
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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 thelist
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 theBadRequest
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 orNone
.
-
add(key, value)
-
Adds a new value for the key.
Changelog
New in version 0.6.
- Parameters
-
- key – the key for the value.
- value – the value to add.
-
clear() → None. Remove all items from D.
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copy()
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Return a shallow copy of this object.
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deepcopy(memo=None)
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Return a deep copy of this object.
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fromkeys(value=None, /)
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Create a new dictionary with keys from iterable and values set to value.
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get(key, default=None, type=None)
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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 aValueError
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 likeget
,getlist
accepts atype
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.
-
items(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.
-
keys() → a set-like object providing a view on D’s keys
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lists()
-
Return a iterator of
(key, values)
pairs, where values is the list of all values associated with the key.
-
listvalues()
-
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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pop(key, default=no value)
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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.
Changelog
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 forkey
.- 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_list – 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
isTrue
the returned dict will only have the first item present, ifflat
isFalse
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(mapping)
-
update() extends rather than replaces existing key lists:
>>> a = MultiDict({'x': 1}) >>> b = MultiDict({'x': 2, 'y': 3}) >>> a.update(b) >>> a MultiDict([('y', 3), ('x', 1), ('x', 2)])
If the value list for a key in
other_dict
is empty, no new values will be added to the dict and the key will not be created:>>> x = {'empty_list': []} >>> y = MultiDict() >>> y.update(x) >>> y MultiDict([])
-
values()
-
Returns an iterator of the first value on every key’s value list.
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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.
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class werkzeug.datastructures.ImmutableMultiDict(mapping=None)
-
An immutable
MultiDict
.Changelog
New in version 0.5.
-
class werkzeug.datastructures.ImmutableOrderedMultiDict(mapping=None)
-
An immutable
OrderedMultiDict
.Changelog
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 theBadRequest
HTTP exception and will render a page for a400 BAD REQUEST
if caught in a catch-all for HTTP exceptions.
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class werkzeug.datastructures.ImmutableDict
-
An immutable
dict
.Changelog
New in version 0.5.
-
class werkzeug.datastructures.ImmutableList(iterable=(), /)
-
An immutable
list
.Changelog
New in version 0.5.
- Private
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class werkzeug.datastructures.FileMultiDict(mapping=None)
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A special
MultiDict
that has convenience methods to add files to it. This is used forEnvironBuilder
and generally useful for unittesting.Changelog
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 afile
-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.Changelog
New in version 0.6.
-
close()
-
Close the underlying file if possible.
-
property content_length
-
The content-length sent in the header. Usually not available
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property content_type
-
The content-type sent in the header. Usually not available
-
property mimetype
-
Like
content_type
, but without parameters (eg, without charset, type etc.) and always lowercase. For example if the content type istext/HTML; charset=utf-8
the mimetype would be'text/html'
.Changelog
New in version 0.7.
-
property 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'}
.Changelog
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,
os.PathLike
, or open file object to write to. -
buffer_size – Passed as the
length
parameter ofshutil.copyfileobj()
.
-
dst – a filename,
Changelog
Changed in version 1.0: Supports
pathlib
.
-
© 2007–2021 Pallets
Licensed under the BSD 3-clause License.
https://werkzeug.palletsprojects.com/en/2.0.x/datastructures/