Python列表生成式和字典生成式实例

[ x  for  x in 可迭代对象]
[ x  for  x in 可迭代对象 if 条件]

In [1]: [x for x in 'abcd']
Out[1]: ['a', 'b', 'c', 'd']

In [1]: res = [10,11,12,13]
In [2]: [x for x in res if x > 10]
Out[2]: [11, 12, 13]

原生实现：
In [1]: arr = []
In [2]: for x in res:
  ....:     if x > 10:
  ....:         arr.append(x)
  ....:         
In [3]: arr
Out[3]: [11, 12, 13]

print [v for k,v in {'a':'one','b':'two'}.items()]
输出：['one', 'two']

print [(k,v) for k,v in {'a':'one','b':'two'}.items()]
输出：[('a', 'one'), ('b', 'two')]

print [k+'='+v for k,v in {'name':'lyz','age':'26','job':'IT'}.items()]
输出：['job=IT', 'age=26', 'name=lyz']

d = dict((key, value) for (key, value) in iterable)

dict1 = {'one':1,'two':2,'three':3}
dict2 = {v:k for k,v in dict1.items()}
print dict2
输出：
{1: 'one', 2: 'two', 3: 'three'}

dict1 = {'one':1,'two':2,'three':3}
dict3 = dict((v,k) for k,v in dict1.items())
print dict3
输出：
{1: 'one', 2: 'two', 3: 'three'}

In [1]: arr=['wd','18','nan']
In [2]: dict((k,v) for k,v in enumerate(arr))
Out[2]: {0: 'wd', 1: '18', 2: 'nan'}
In [3]: {k:v for k,v in enumerate(arr)}
Out[3]: {0: 'wd', 1: '18', 2: 'nan'}

arr = [{'id':1,'name':'lyz','age':26},{'id':2,'name':'pc','age':30}]
print {str(x['id']):x['name'] for x in arr}
执行结果：
{'1': 'lyz', '2': 'pc'}

>>> a = [(1, 'ab'), (2, 'bc')]
>>> dict(a)
{1: 'ab', 2: 'bc'}

>>> result = ((1, 'ab'), (2, 'bc'))
>>> dict(result)
{1: 'ab', 2: 'bc'}

In [1]: zip(('name','age','sex'),('wd','18','nan'))
Out[1]: [('name', 'wd'), ('age', '18'), ('sex', 'nan')]

In [2]: zip(['name','age','sex'],['wd','18','nan'])
Out[2]: [('name', 'wd'), ('age', '18'), ('sex', 'nan')]

In [3]: dict(zip(('name','age','sex'),('wd','18','nan')))  # 生产环境最常用
Out[3]: {'age': '18', 'name': 'wd', 'sex': 'nan'}

In [4]: zip(['name','age','sex'],['wd','18','nan'],['11',22])  # 列表元素个数不一致，以最少对列表为准
Out[4]: [('name', 'wd', '11'), ('age', '18', 22)]