python dict合并_Python 中两个字典(dict)合并

dict1={1:[1,11,111],2:[2,22,222]}

dict2={3:[3,33,333],4:[4,44,444]}

合并两个字典得到类似

{1:[1,11,111],2:[2,22,222],3:[3,33,333],4:[4,44,444]}

方法1:

dictMerged1=dict(dict1.items()+dict2.items())

方法2:

dictMerged2=dict(dict1, **dict2)

方法2等同于:

dictMerged=dict1.copy()

dictMerged.update(dict2)

或者

dictMerged=dict(dict1)

dictMerged.update(dict2)

方法2比方法1速度快很多,用timeit测试如下

$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged1=dict(dict1.items()+dict2.items())'

10000 loops, best of 3: 20.7 usec per loop

$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged2=dict(dict1,**dict2)'

100000 loops, best of 3: 6.94 usec per loop

$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged3=dict(dict1)' 'dictMerged3.update(dict2)'

100000 loops, best of 3: 7.09 usec per loop

$ python -m timeit -s 'dict1=dict2=dict((i,i) for i in range(100))' 'dictMerged4=dict1.copy()' 'dictMerged4.update(dict2)'

100000 loops, best of 3: 6.73 usec per loop

list新增元素使用append方法。并不像php中 直接$array[]='xxx';

>>> a=[]

>>> a.append('bbb');

>>> b={'test':'bbbbbbbbbbb'}

>>> a.append(b);

>>> a

['bbb', {'test': 'bbbbbbbbbbb'}]

>>> c={'cc':"cccccccccccc"}

>>> a[4]=100

Traceback (most recent call last):

File "", line 1, in

IndexError: list assignment index out of range

>>> print a

['bbb', {'test': 'bbbbbbbbbbb'}]

>>> a[2]=100

Traceback (most recent call last):

File "", line 1, in

IndexError: list assignment index out of range

>>> a[1]=100

>>> print a

['bbb', 100]

>>> a[4]=100

Traceback (most recent call last):

File "", line 1, in

IndexError: list assignment index out of range

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