字典的添加

>>> d = {}
>>> d[1] = 1
>>> d
{1: 1}
>>> d.setdefault(2, 2)
2
>>> d
{1: 1, 2: 2}
>>> d.update({3:3})
>>> d
{1: 1, 2: 2, 3: 3}

>>> d + {6: 6}
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'dict' and 'dict'

字典没有加法运算

字典的删除

>>> d = {1: 1, 2: 2, 3: 3}

>>> d.pop(1)
1
>>> d
{2: 2, 3: 3}
>>> d.pop(6)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 6

>>> del d[2]
>>> d
{3: 3}
>>> del d[6]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 6

索引不存在时会报出IndexError的错误

字典的访问

>>> d = {1: 1, 2: 2, 3: 3}

>>> d[1]
1
>>> d[6]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
KeyError: 6

>>> d.get(6) == None
True
>>> d.get(6, 6)
6

>>> d.setdefault(1)
1
>>> d
{1: 1, 2: 2, 3: 3}
>>> d.setdefault(6, 6)
6
>>> d
{1: 1, 2: 2, 3: 3, 6: 6}

索引不存在时会报出IndexError的错误

字典的更新

>>> d = {1: 1, 2: 2, 3: 3}

>>> d[2] = 6
>>> d
{1: 1, 2: 6, 3: 3}
>>> d.update({2:2})
>>> d
{1: 1, 2: 2, 3: 3}

>>> d.setdefault(2, 6)
2
>>> d
{1: 1, 2: 2, 3: 3}
>>> d.setdefault(6, 6)
6
>>> d
{1: 1, 2: 2, 3: 3, 6: 6}

字典推导式

>>> d = {1: 1, 2: 2, 3: 3, 4: 4, 5: 5, 6: 6}
>>> d = {k: v for k, v in d.items() if k % 2 == 1}
>>> d
{1: 1, 3: 3, 5: 5}

其他创建方式

二元组创建

>>> d = dict([(1, 1), (2, 2), (3, 3)])
>>> d
{1: 1, 2: 2, 3: 3}

默认值创建

>>> d = dict.fromkeys(range(3), 0)
>>> d
{0: 0, 1: 0, 2: 0}