Python常用指令

import time
import os

time.sleep()    #延时
time.clock()    #第一次调用返回程序运行的实际时间；第二次调用返回第一次调用后到这次调用的时间间隔
time.time()     #当前时间戳
time.ctime()    #当前时间的字符串形式

os.getcwd()     #获取当前脚本路径
os.chdir('D:\\') #修改当前路径
os.linesep      #当前环境下的换行分隔符
os.system('pause')  #按任意键继续

---

执行外部.py文件

os.chdir(r'D:\test.py')
exec(compile(open(r'D:\test.py').read(),r'D:\test.py','exec'))

---

带index的枚举

for index, item in enumerate(items):
    print(index, item)

---

字符串合并

l = ['one', 'two', 'three']
s = ''.join(l)    #s='onetwothree'

字符串分割用str.split(sep=None, maxsplit=-1)

'1,2,,3,'.split(',')
#输出['1', '2', '', '3', '']
'   1   2   3   '.split()
#输出['1', '2', '3'] 自动合并空格
items = 'zero one two three'.split()
#方便的单词list初始化

行分割用str.splitlines([keepends])
自动舍弃空行，常用于文件操作
更复杂的要求可用re.split(pattern, string, maxsplit=0, flags=0)

---

显示正则表达式推导树

re.compile("^\[font(?:=(?P[-+][0-9]{1,2}))?\](.*?)[/font]",
    re.DEBUG)

添加注释的正则表达式

pattern = """
^                   # beginning of string
M{0,4}              # thousands - 0 to 4 M's
(CM|CD|D?C{0,3})    # hundreds - 900 (CM), 400 (CD), 0-300 (0 to 3 C's), or 500-800 (D, followed by 0 to 3 C's)
(XC|XL|L?X{0,3})    # tens - 90 (XC), 40 (XL), 0-30 (0 to 3 X's), or 50-80 (L, followed by 0 to 3 X's)
(IX|IV|V?I{0,3})    # ones - 9 (IX), 4 (IV), 0-3 (0 to 3 I's), or 5-8 (V, followed by 0 to 3 I's)
$                   # end of string
"""

re.search(pattern, 'M', re.VERBOSE)

---

从字符串创建对应名字的类对象

class ButtonFactory():
    def create_button(self, typ):
        targetclass = typ.capitalize()
        return globals()[targetclass]()

使用方法

button_obj = ButtonFactory()
button_obj.create_button('button').

---

线程之间队列

def worker():
    while True:
        item = q.get()
        do_work(item)
        q.task_done()
q = Queue()
for i in range(num_worker_threads):
     t = Thread(target=worker)
     t.daemon = True
     t.start()
for item in source():
    q.put(item)
q.join()
#Queue除了提供常规的阻塞/非阻塞put() get()外，还实现了一组取决于计数的阻塞机制：每当添加元素时计数增加1，task_down()计数减1，join()阻塞直至计数归零

---

参数列表

def draw(x, y):
    # do some magic

point_foo = (3, 4)
point_bar = {'y': 4, 'x': 3}

draw_point(*point_foo)
draw_point(**point_bar) #对应参数名的字典

---

tuple多赋值与深度拷贝

import copy
m = [1, 2, [3, 4]]
a = m
b = m.copy()
b1, b2, b3 = m
c1, c2, c3 = copy.deepcopy(m)

m[1] = 20
m[2][0] = 30

print(a)
print(b)
print(b1, b2, b3)
print(c1, c2, c3)

运行结果：

[1, 20, [30, 4]]
[1, 2, [30, 4]]
1 2 [30, 4]
1 2 [3, 4]

---

pprint.pprint可产生相应对象的构造字符串
若更为精细地进行对象序列化，则使用Pickling
序列化

import pickle
data = {'foo': [1,2,3],
                'bar': ('Hello', 'world!'),
                'baz': True}
jar = open('data.pkl', 'wb')
pickle.dump(data, jar) # 将pickle后的数据写入jar文件
jar.close()

反序列化

import pickle
pkl_file = open('data.pkl', 'rb')
data = pickle.load(pkl_file)
print data
pkl_file.close()

---

total = sum([num * num for num in range(1, 101)])

#lazy生成器
total = sum(num * num for num in xrange(1, 101))

---

集合操作

>>> a = set([1,2,3,4])
>>> b = set([3,4,5,6])
>>> a | b # Union
{1, 2, 3, 4, 5, 6}
>>> a & b # Intersection
{3, 4}
>>> a < b # Subset
False
>>> a - b # Difference
{1, 2}
>>> a ^ b # Symmetric Difference
{1, 2, 5, 6}

---

模块结构规范

"""module docstring"""

# imports
# constants
# exception classes
# interface functions
# classes
# internal functions & classes

def main(...):
    ...

if __name__ == '__main__':
    status = main()
    sys.exit(status)

---

magic function内置函数隐含调用列表
http://www.rafekettler.com/magicmethods.html
常用：

__getattr__(self, name): 
    self.name 当name不存在时

__setattr__(self, name, val)
    self.name = val 当name不存在时

__iter__(self)  
    for x in self   迭代器

__getitem__(self, key)  
    self[key] 下标索引访问

__setitem__(self, key, val) 
    self[key] =val 下标索引赋值

__index__(self)
    x[self] 作为数组下标时