Python高级应法

__builtins__.end = None  加这句话Python可以在if后面使用end
>>> a
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined
>>> d = {'a': 1, 'b':2}
>>> # 粗暴的写法
>>> for k, v in d.iteritems():
...     exec "{}={}".format(k, v)
...
>>> # 文艺的写法
>>> globals().update(d)
>>> a, b
(1, 2)
>>> 'a', 'b'
('a', 'b')
>>> globals()['a'] = 'b'
>>> a
'b'



字符串格式化
>>> "{key}={value}".format(key="a", value=10) # 使⽤命名参数
'a=10'
>>> "[{0:<10}], [{0:^10}], [{0:*>10}]".format("a") # 左中右对⻬
'[a         ], [    a     ], [*********a]'
>>> "{0.platform}".format(sys) # 成员
'darwin'
>>> "{0[a]}".format(dict(a=10, b=20)) # 字典
'10'
>>> "{0[5]}".format(range(10)) # 列表
'5'
>>> "My name is {0} :-{{}}".format('Fred') # 真得想显示{},需要双{}
'My name is Fred :-{}'
>>> "{0!r:20}".format("Hello")
"'Hello'             "
>>> "{0!s:20}".format("Hello")
'Hello               '
>>> "Today is: {0:%a %b %d %H:%M:%S %Y}".format(datetime.now())
'Today is: Mon Mar 31 23:59:34 2014'

>>> dict((["a", 1], ["b", 2])) # ⽤两个序列类型构造字典
{'a': 1, 'b': 2}
>>> dict(zip("ab", range(2)))
{'a': 0, 'b': 1}
>>> dict(map(None, "abc", range(2)))
{'a': 0, 'c': None, 'b': 1}
>>> dict.fromkeys("abc", 1) # ⽤序列做 key,并提供默认 value
{'a': 1, 'c': 1, 'b': 1}
>>> {k:v for k, v in zip("abc", range(3))} # 字典解析
{'a': 0, 'c': 2, 'b': 1}
>>> d = {"a":1, "b":2}
>>> d.setdefault("a", 100) # key 存在,直接返回 value
1
>>> d.setdefault("c", 200) # key 不存在,先设置,后返回
200
>>> d
{'a': 1, 'c': 200, 'b': 2}


字典视图
>>> d1 = dict(a = 1, b = 2)
>>> d2 = dict(b = 2, c = 3)
>>> d1 & d2 # 字典不⽀支持该操作
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for &: 'dict' and 'dict'
>>> v1 = d1.viewitems()
>>> v2 = d2.viewitems()
>>> v1 & v2 # 交集
set([('b', 2)])
>>> dict(v1 & v2) # 可以转化为字典
{'b': 2}
>>> v1 | v2 # 并集
set([('a', 1), ('b', 2), ('c', 3)])
>>> v1 - v2 #差集(仅v1有,v2没有的)
set([('a', 1)])
>>> v1 ^ v2 # 对称差集 (不会同时出现在 v1 和 v2 中)
set([('a', 1), ('c', 3)])
>>> ('a', 1) in v1 #判断
True
迭代器与生成器：http://www.cnblogs.com/tqsummer/archive/2010/12/27/1917927.html

python静态类方法 http://blog.csdn.net/xluren/article/details/9168535Python



http://www.360doc.cn/article/9482_373285413.html?plg_nld=1&plg_uin=1&plg_auth=1&plg_nld=1&plg_usr=1&plg_vkey=1&plg_dev=1  python 动态扩展包stevedore


>>> import xml.etree.ElementTree as etree
>>> tree=etree.parse('test.xml')
>>> root=tree.getroot()
>>> root
<Element 'note' at 0x7fa6d3c8e510>
>>> root.tag
'note'
>>> len(root)
4
>>> for child in root:
...     print(child)
...
<Element 'to' at 0x7fa6d3c8e550>
<Element 'from' at 0x7fa6d3c8e590>
<Element 'heading' at 0x7fa6d3c8e650>
<Element 'body' at 0x7fa6d3c8e710><Element 'note' at 0x7fa6d3c8e510>


import pickle
with open('entry.pickle', 'wb') as f:
...     pickle.dump(entry, f)
with open('entry.pickle','rb') as f:
...     entry = pickle.load(f)