python-dict内置函数

字典内置函数

class dict(object)
| dict() -> new empty dictionary
| dict(mapping) -> new dictionary initialized from a mapping object’s
| (key, value) pairs
| dict(iterable) -> new dictionary initialized as if via:
| d = {}
| for k, v in iterable:
| d[k] = v
| dict(**kwargs) -> new dictionary initialized with the name=value pairs
| in the keyword argument list. For example: dict(one=1, two=2)
| Methods defined here:
| __contains__(self, key, /)
| True if the dictionary has the specified key, else False.
| __delitem__(self, key, /)
| Delete self[key].
| __eq__(self, value, /)
| Return selfvalue.
| __ge__(self, value, /)
| Return self>=value.
| __getattribute__(self, name, /)
| Return getattr(self, name).
| __getitem__(…)
| x.getitem(y) <> x[y]
| __gt__(self, value, /)
| Return self>value.
| __init__(self, /, *args, **kwargs)
| Initialize self. See help(type(self)) for accurate signature.
| __iter__(self, /)
| Implement iter(self).
| __le__(self, value, /)
| Return self<=value.
| __len__(self, /)
| Return len(self).
| __lt__(self, value, /)
| Return self<value.
| __ne__(self, value, /)
| Return self!=value.
| __repr__(self, /)
| Return repr(self).
| __setitem__(self, key, value, /)
| Set self[key] to value.
| __sizeof__(…)
| D.__sizeof__() -> size of D in memory, in bytes
以下为字典的内置函数
| clear(…)
| D.clear() -> None. Remove all items from D.
清除，将字典内所有元素都删光

>>> a = {1:'2'}
>>> a.clear()
>>> a
{}

| copy(…)
| D.copy() -> a shallow copy of D
将字典进行拷贝

>>> a = {1:1}
>>> b = a.copy()
>>> a
{1: 1}
>>> b
{1: 1}

| get(self, key, default=None, /)
| Return the value for key if key is in the dictionary, else default.
根据所给的key来查找字典内的所对应的值，如果没有，则返回default所给定的值，默认为None

>>> a = {1:'1'}
>>> a.get(1)
'1'
>>> a.get(2,'no 2')
'no 2'

| items(…)
| D.items() -> a set-like object providing a view on D’s items
以字典独有的一种dict_items类型将字典内所有键值对按照元组的方式返回

>>> a = {1:1,2:2,3:3}
>>> a.items()
dict_items([(1, 1), (2, 2), (3, 3)])
>>> type(a.items())
<class 'dict_items'>

| keys(…)
| D.keys() -> a set-like object providing a view on D’s keys
以字典独有的dict_keys返回字典内所有的键

>>> a = {1:1,2:2,3:3}
>>> a = a.keys()
>>> a
dict_keys([1, 2, 3])
>>> type(a)
<class 'dict_keys'>

| pop(…)
| D.pop(k[,d]) -> v, remove specified key and return the corresponding value.
| If key is not found, d is returned if given, otherwise KeyError is raised
删除给定的键并且返回键所对应的值，如果键不存在，但是给了一个默认值，则返回默认值，如果没有默认值则报错

>>> a = {1:1,2:2,3:3}
>>> a.pop(1)
1
>>> a
{2: 2, 3: 3}
>>> a.pop(4)
Traceback (most recent call last):
  File "<pyshell#24>", line 1, in <module>
    a.pop(4)
KeyError: 4
>>> a.pop(4,'no 4')
'no 4'

| popitem(…)
| D.popitem() -> (k, v), remove and return some (key, value) pair as a
| 2-tuple; but raise KeyError if D is empty.

删除字典最后一组键值对，并且返回这个键值对，如果字典为空，则报错

>>> a = {1:1,2:2,3:3}
>>> a.popitem()
(3, 3)
>>> a
{1: 1, 2: 2}
>>> a.popitem()
(2, 2)
>>> a.popitem()
(1, 1)
>>> a.popitem()
Traceback (most recent call last):
  File "<pyshell#38>", line 1, in <module>
    a.popitem()
KeyError: 'popitem(): dictionary is empty'

| setdefault(self, key, default=None, /)
| Insert key with a value of default if key is not in the dictionary.
| Return the value for key if key is in the dictionary, else default.

根据所给的key查找字典中是否存在这个值，如果存在则返回key所以对应的值，如果不存在则按照所给的键和默认值插入字典，如果没给默认值也不存在该键，则创建一个值为None的键值对

>>> a = {1:1,2:2,3:3}
>>> a.setdefault(2)
2
>>> a
{1: 1, 2: 2, 3: 3}
>>> a.setdefault(2,20)
2
>>> a
{1: 1, 2: 2, 3: 3}
>>> a.setdefault(20,20)
20
>>> a
{1: 1, 2: 2, 3: 3, 20: 20}
>>> a.setdefault(21)
>>> a
{1: 1, 2: 2, 3: 3, 20: 20, 21: None}

| update(…)
| D.update([E, ]**F) -> None. Update D from dict/iterable E and F.
| If E is present and has a .keys() method, then does: for k in E: D[k] = E[k]
| If E is present and lacks a .keys() method, then does: for k, v in E: D[k] = v
| In either case, this is followed by: for k in F: D[k] = F[k]

跟新，根据所给的字典进行查找，如果相应的键，则进行修改值，如果不存在则创建该键值对

>>> a = {1:1,2:2,3:3}
>>> a.update({5:5})
>>> a
{1: 1, 2: 2, 3: 3, 5: 5}
>>> a.update({1:5})
>>> a
{1: 5, 2: 2, 3: 3, 5: 5}

| values(…)
| D.values() -> an object providing a view on D’s values
以字典独有的dict_values返回字典内所有的键

>>> a = {1:1,2:2,3:3}
>>> a = a.values()
>>> a
dict_values([1, 2, 3])
>>> type(a)
<class 'dict_values'>

| ----------------------------------------------------------------------
| Class methods defined here:
|
| fromkeys(iterable, value=None, /) from builtins.type
| Create a new dictionary with keys from iterable and values set to value.

Static methods defined here:
__new__(*args, **kwargs) from builtins.type
Create and return a new object. See help(type) for accurate signature.
----------------------------------------------------------------------
Data and other attributes defined here:
__hash__= None