Python_Tips

• 时间字符串

• python拼接字符串的方法

• python中创建字典的方法

• python中字典合并的四种方法

• 启动下载服务器

• 将字符串转为json

• 检查第三方库是否正确安装

• 变量互换

• 比较操作和逻辑and

• 使用三元操作符来进行条件赋值

• 多行字符串

• 解包

• 语句执行结果

• 列表和字符串反转

时间字符串

>>> import time
>>> d = time.strftime('%Y-%m-%d', time.gmtime(time.time()))
>>> d
'2018-12-24'
>>> 

python拼接字符串的方法

>>> s = 'Hello' + ' ' + 'World' + '!'
>>> print s
Hello World!
>>> 
>>> strlist = ['Hello', ' ', 'World', '!']
>>> print ''.join(strlist)
Hello World!
>>> 
>>> s = '{} {}!'.format('Hello','World')
>>> print s
Hello World!
>>> 
>>> s = '%s %s!' % ('Hello', 'World')
>>> print s
Hello World!
>>> 
>>> s = (
... 'hello'
... ' '
... 'world'
... '!')
>>> print s
hello world!
>>> 
>>> from string import Template
>>> s = Template('${s1} ${s2}!') 
>>> print s.safe_substitute(s1='Hello', s2='World!')
Hello World!!
>>> 

python中字典合并的四种方法

>>> d1 = {"user": "lilei", "pwd": "123456"}
>>> d2 = {"host": "127.0.0.1", "port": 10010}
>>> d3 = dict(d1.items() + d2.items())
>>> print d3 
{'host': '127.0.0.1', 'pwd': '123456', 'user': 'lilei', 'port': 10010}
>>> 
>>> d1 = {"user": "lilei", "pwd": "123456"}
>>> d2 = {"host": "127.0.0.1", "port": 10010}
>>> d3 = {}
>>> d3.update(d1)
>>> d3.update(d2)
>>> print d3 
{'host': '127.0.0.1', 'pwd': '123456', 'user': 'lilei', 'port': 10010}
>>> 
>>> d1 = {"user": "lilei", "pwd": "123456"}
>>> d2 = {"host": "127.0.0.1", "port": 10010}
>>> d3 = dict(d1, **d2)
>>> print d3 
{'host': '127.0.0.1', 'pwd': '123456', 'user': 'lilei', 'port': 10010}
>>> 
# python3
>>> d1 = {"user": "lilei", "pwd": "123456"}
>>> d2 = {"host": "127.0.0.1", "port": 10010}
>>> d3 = {**d1, **d2}
>>> print(d3)
{'user': 'lilei', 'pwd': '123456', 'host': '127.0.0.1', 'port': 10010}
>>> 

启动下载服务器

$ cd /tmp  # 进入要下载文件所在目录
$ python -m SimpleHTTPServer
Serving HTTP on 0.0.0.0 port 8000 ...

$ nohup python -m SimpleHTTPServer 1666 &

$ python3 -m http.server  # python3

wget 10.1.36.27:8000/backup-2019_05_24.zip -O backup-2019_05_24.zip

将字符串转为json

$ echo '{"job":"developer", "name":"lanzhiwang"}' | python -m json.tool 
{
    "job": "developer",
    "name": "lanzhiwang"
}
$ 

检查第三方库是否正确安装

$ python -c "import numpy"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ImportError: No module named numpy
$ 

变量互换

>>> x, y = 10, 20
>>> print x, y
10 20
>>> 
>>> y, x = x, y
>>> print x, y
20 10
>>> 

比较操作和逻辑and

>>> n = 10
>>> result = 1 < n < 20
>>> print result
True
>>> 
>>> result = 1 >= n < 20
>>> print result
False
>>> 

使用三元操作符来进行条件赋值

>>> x = 50
>>> y = 10 if (x == 50) else 20
>>> print y
10
>>> 

多行字符串

>>> multiStr = """select * from multi_row
... where row_id < 5
... order by age"""
>>> 
>>> print multiStr
select * from multi_row
where row_id < 5
order by age
>>> 
>>> multiStr = ("select * from multi_row "
... "where row_id < 5 "
... "order by age")
>>> 
>>> print multiStr
select * from multi_row where row_id < 5 order by age
>>> 

解包

>>> testList = [1, 2, 3]
>>> x, y, z = testList
>>> print x, y, z
1 2 3
>>> 

语句执行结果

>>> 1 + 2
3
>>> _
3
>>> print _
3
>>> 

列表和字符串反转

>>> testList = [1, 2, 3]
>>> print testList
[1, 2, 3]
>>> 
>>> testList = testList[::-1]
>>> print testList
[3, 2, 1]
>>> 
>>> testStr = "qwertyuiop"
>>> print testStr
qwertyuiop
>>> 
>>> testStr = testStr[::-1]
>>> print testStr
poiuytrewq
>>>