Get args in specific position and pack the rest

>>> a, *b, c, d = range(10)
>>> a
0
>>> b
[1, 2, 3, 4, 5, 6, 7]
>>> c
8
>>> d
9

Return the last value if a seires a value is all True, otherwise get the first value equavilent to False

rc = 1 and 2 and 3
>>> rc
3
rc2 = 'aa' and False and 0
>>> rc2

False

Else if in single expression

List Comprehension

>>> [i if i < 0 else (i, 2) if i%2 == 0 else "good" if 1 < i < 10 else 'bad' for i in range(10)]
[(0, 2), 'bad', (2, 2), 'good', (4, 2), 'good', (6, 2), 'good', (8, 2), 'good']

lambda function

complicate_lambda_func = lambda *args, **kwargs: \
    "No message" if len(args) + len(kwargs) < 2  \
    else "Yes, sir!" if ('id' in kwargs and kwargs['id'] == 'General') \
    else "There is no door for you" if 'alibaba' in args \
    else "It's already long enough, let's top here"

>>> complicate_lambda_func(1,2,3)
"It's already long enough, let's top here"
>>> complicate_lambda_func(command='fuck me', id='General')
'Yes, sir!'
>>> complicate_lambda_func("老乡", "开门啊", "我是", 'alibaba')
'There is no door for you'

看完上面两个例子，我越发觉得elif是源自于 else value if conditon 的表达方式了。
不过与elif不同的时候，上述例子的else if表达式最后一定得跟一个单纯的else语，不然报错在等着你！

Unpacking Argument Lists

在python里你可以使用*来给函数定义可接受任意个参数。同时你也可以用*来将一个iterator unpack成一系列args传给函数!
str, list, tuple, dict都可以使用这个技术，不过dict出来的参数顺序可能是乱的，因为hash的特性。

def print_args(*args):
    print " -- ".join(map(str, args))

# Str
>>> print_args(*"Monster")
M -- o -- n -- s -- t -- e -- r

# List
>>> print_args(*range(5))
0 -- 1 -- 2 -- 3 -- 4

# Tuple
>>> print_args(*("Harry Poter", "Princess White"))
Harry Poter -- Princess White

# Dict
>>> print_args(*{"a":1, "b":2, "c":3, "d":4})
a -- c -- b -- d

Format String with dictionray variables

my_dict = {
    'my_name': 'Z',
    'my_age': 3,
    'my_toy': (set([1,2,3]), {1:2, 3:4}, [5,6,7])
}

print('my name is {my_name}, my age is {my_age}, my toy is {my_toy}'.format(**my_dict))

my name is Z, my age is 3, my toy is ({1, 2, 3}, {1: 2, 3: 4}, [5, 6, 7])

format支持*args和**kwargs, 也就是说你可以用"{0}, {1}, x".format(a, b, x=val)来format args 和 kwargs. 最前面部分的0和1分别代表第1个argument和第二个argument. 你甚至可以用'{0.attr_name}'.format(arg1)来调用第一个argument的属性。

如： In []: '{0.denominator}'.format(-1) Out[]: '1'

In []: '{1.count}'.format(0, 'sth')
Out[]: '<built-in method count of str object at 0x107821ab0>'

对原函数/类方法进行inspect/审查的decorator

import random

def function_inspector(func):
    def new_func(*args, **kwargs):
        Lucky_number = [6, 7, 8, 9]
        result = func(*args, **kwargs)
        if type(result) == int and result in Lucky_number:
            return result, "You are Lucky"
        else:
            return result
    return new_func

@function_inspector
def lottery():
     return random.choice(range(10))

>>> lottery()
3
>>> lottery()
(8, 'You are Lucky')


def method_inspector(method):
    BANNED_WEBSITES = ['google', 'facebook', 'youtube', 'twitter']
    BANNED_WORDS = ['法轮功', '共产党']

    def new_method(self, *args, **kwargs):  # 此处的self参数是为了对类方法进行inspect所加
        if getattr(self, 'name', None) in BANNED_WEBSITES:
            return "404 网站无法访问"
        result = method(self, *args, **kwargs)
        for i in result:
            if type(i) != str:
                continue
            for banned_word in BANNED_WORDS:
                if banned_word in i:
                    return "该网站含有不恰当内容"
        return result

    return new_method

将url中特殊字符(% + alphanum表示的那些字符)进行转换

import urllib
converted_str = urllib.unquote(raw_url_str)

想要把特殊符号再转回成url中的%编码字符，你用 reconverted_str = urllib.quote(converted_str)

使用文件名字符进行from m import *操作

agent = importlib.import_module(module_name)
globals().update(vars(agent))

将一个python数据转换成json格式

import json
converted_json_data = json.dumps(raw_python_data)

一行代码反转字典键值对(需要每个值都是独特的才可以）

inv_map = {v:k for k,v in my_dict.items()}

查看当前python进程使用的内存大小

import resource
mem_usage = resource.getrusage(resource.RUSAGE_SELF)
print mem_usage.ru_maxrss

# OSX 下的单位是byte, 而Linux下的单位是kilobyte
# 将RUSAGE_SELF 换成 RUSAGE_CHILDREN 来查看子进程的内存占用

获得当前文件路径

import os
os.path.dirname(os.ptah.abspath(__file__))      # 文件存储路径
os.getcwd()                                     # 当前所在的执行

检测一个对象是否是字符串(包括普通字符和unicode字符)

isinstance(obj, basestring)

Log detailed error info without exit python process

import traceback
import sys
try:
    eval('Your Arbitary Code here')
except:
    print 'This is diy error log'
    print traceback.format_exc()
    print sys.exc_info()

DATA STRUCTURE

SET OPERATION

UNION               s | t           #  all elements in s and t, except duplicate
INTERSECTION        s & t           #  elements that are in s and t
DIFERENCE           s - t           #  element in s but not in t
SYMMETRIC_DIFFER    s ^ t           #  equal to (s - t) | (t - s), means that element in t or s that are not appeared in both set

DATETIME AND TIME

获取当前自然日的日期字符串

from datetime import datetime
natural_date = str(datetime.now().date())

快速将字符串解析成datetime对象

需要先安装py-dateutil

from dateutil import parser
datetime_obj = parser.parse(datetime_str, fuzzy=True)

fuzzy=True会开启模糊模式，忽略一些parser不能识别的字符

快速打印格式化的当前年月日和时分秒

import time
time.strftime('%F %T')
# %F 是年月日在time模块里的快捷表示，%T是时分秒的快捷表示, 样例：2015-01-01 00:00:00

Python 3 magic